The radiological health significance of cardiovascular special procedures

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The radiological health significance of cardiovascular special procedures
Properzio, William Stuart, 1940-
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xx, 291 leaves : ill. ; 28cm.


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Adults ( jstor )
Aprons ( jstor )
Bone marrow ( jstor )
Cardiac surgical procedures ( jstor )
Dosage ( jstor )
Employee assistance programs ( jstor )
Energy value ( jstor )
Heart catheterization ( jstor )
Pediatrics ( jstor )
Physicians ( jstor )
Cardiac catheterization ( lcsh )
Dissertations, Academic -- Environmental Engineering Sciences -- UF
Environmental Engineering Sciences thesis Ph. D
Radiation dosimetry ( lcsh )
bibliography ( marcgt )
non-fiction ( marcgt )


Thesis--University of Florida.
Bibliography: leaves 280-289.
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by William Stuart Properzio.

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ACKNOVJLEDGMENTS I would like to recognize my employer, the Bureau of Radiological Health of the Food and Drug Administration, U.S. Department of Health, Education and Welfare for the opport'onity they provided me to pursue graduate study and work on this project. In addition to the chairman and members of my committee who have contributed advice and guidance throughout this study, I would like to recognize Mr. Schuyler Hardin, Technical Director of the University of Florida Cardiovascular Laboratory. Sky's interest and willingness to provide me v/ith v/hatever v;as necessary to accomplish the goals of the project are sincerely appreciated, The success of the field survey phase of the study was made possible through the cooperation of Mr. William Eldridge of the Radiological Health Section of the Florida Division of Health. The two pediatric phantoms were specially fabricated by Mr, Emmett Murphy of Gaithersburg, Maryland. Murph is a friend and professional associate and in the fabrication of these test phantoms has shown he has lost none of the energy and originality ho was noted for prior to his retirement. Finally I would like to thank my family for their support and encouragement.


TABLE OF CONTENTS ACKNOWLEDGMENTS LIST OF TABLES LIST OF FIGURES ABSTRACT CHAPTER I INTRODUCTION Objectives of Study II CARDIOVASCULAR X-RAY PRACTICES Nine Florida Facilities University of Florida Cardiovascular Laboratory Equipment Patient and Examination Trends III RADIATION MEASUREI4ENT EQUIPMENT AND TECHNIQUES Thermoluminescent Dosim.etry Linearity of Calibration Factor v/ith Exposure Level Dosim.eter Package . Victoreen 555 System Exposure Area Product Measurement Instruraentation of X-ray Unit PAGE ii viii xiv X vi i i 1 5 7 7 19 19 26 34 34 41 44 46 51 53


TABLE OF CONTENTS Continued CHAPTER PAGE III Exposure Area Product Meter Calibration 56 Effect of backscatter. . 59 Energy dependence 60 IV RADIATION EXPOSURE TO CLINICAL PERSONNEL 63 Literature Review 65 Recorded Personnel Exposures in Ten Catheterization Laboratories . . 71 Personnel Exposure Measurements in University of Florida Cardiovasci_lar Laboratory 74 Scatter Levels Around Examination Tables 89 Exposure Measurements for Under Table X-ray Source 91 Expected Exposures for Other Configurations 100 Protective Lead Aprons 105 V PATIENT EXPOSURE STUDY GENERAL CONSIDERATIONS 112 Prospective Cardiac Catheterization Patients ...... 113 Review of Published Dosimetry Studies 117 Need for Patient Dosim.etry Study 12 2 VI PATIENT EXPOSUPvE STUDY PHAI'^TOM MEASUREMENTS 123


TABLE OF CONTENTS Continued CHAPTER PAGE VI Description of Phantoms 124 Phantom Dosimetry Sites 127 Adult Bone Marrow-/ Sites 136 Pediatric Bone Marrow Sites.. 138 Method of Interpreting Dosimetry Data 140 Dose to the Lens of the Eye.. 140 Dose to Reproductive Organs.. 143 Bone Marrow Dose 144 Phantom Dosimetry Results 151 VII PATIENT EXPOSUP^ STUDY CLINICAL PATIENT MEASUREMENTS 15 8 Methodology 15 8 Results of Patient Monitoring .... 160 Results of S\±)sample Monitoring with TLD 166 Group I Results 167 Group II Results 167 Intercomparison of Dosimetry Techniques 177 Incident Exposure 177 EAP Measurements 186


TABLE OF CONTENTS Continued CHAPTER PAGE VII Selected Surface Sites 186 Population Predictions 191 Comparison with Other Published Data 195 VIII SUMi^'lARY AND CONCLUSIONS 19 8 Personnel Exposure 19 8 Patient Exposure 201 X-ray Equipment Alternatives 20 3 Pulsed Fluoroscopy 204 Fluorography 20 8 Application of Predictions to Patient Data 211 Radiation Protection Criteria for Cardiac Catheterization Facilities 212 Equipment and Facility Design 215 Beam limitation for fluoroscopy, cine and spot film fluorography 215 Primary beam 216 Scatter 216 Mechanism for primary physician to monitor operational status of x-ray system 218 Dose reduction in relation to mode of imaging... 219 Fluoroscopic timer 219


TABLE OF CONTENTS Continued CHAPTER VIII Method of quality control of the radiologic facility Examination and Operational Techniques Personnel Radiation monitoring Design of lead apron Position of personnel during x-ray . . . Patient exposure Patient exposure records Dose to reproductive organs Identification of film Cine quality control... APPENDIX A X-RAY CHARACTERISTICS B PATIENT AGE AND FLUORO TIME C TLD STATISTICAL ANALYSIS D PERSONNEL EXPOSURE DATA E BONE MARROVJ DISTRIBUTION AND EXPOSURE FACTORS F INTEGPAJ. DOSE REFERENCES BIOGRAPHICAL SKETCH PAGE 220 2 21 221 221 223 223 224 224 225 227 227 229 239 246 251 261 269 280 290


LIST OF TABLES TABLE PAGE 1 Organization and Operational Characteristics for Nine Cardiac Catheterization Facilities 9 2 Operating Personnel Structure for Nine Cardiac Catheterization Facilities ... 10 3 X-ray Equipment Configuration in Nine Cardiac Catheterization Facilities ... 13 4 Radiological Health Characteristics Associated with Cardiac Catheterization Facilities 16 5 Measured First Half Value Layer for Various X-ray Source and Patient Geometries 24 6 Frequency of Cardiac Catheterization Examinations in the University of Florida Cardiovascular Laboratory .... 29 7 Free Air Chamber Calibration of Victoreen 555 47 8 Energy Dependence of PTW Exposure Area Product Measurement Chamber 62 9 Reported Physician Exposure per Procedure at Indicated Site 68 10 Occupational Exposure by Employer Classification with Breakout of Values for Medical Related Areas 70 11 Personnel Monitoring Records for Individuals Involved with the Conduct of Cardiac Catheterization Procedures 73


LIST OF TABLES Continued TABLE 12 S\iinmary of Measured Exposures to Physicians During Cardiac Catheterization Examinations PAGE 79 13 Summary of Measured Exposures to Technicians During Cardiac Catheterization Examinations on Adult Patients 80 14 Summary of Measured Exposures to Technicians During Cardiac Catheterization Examinations on Pediatric Patients... 81 15 Red Bone Marrov/ Distribution in Body Zones Identified in Figure 17 88 16 Estimated Yearly Occupational Exposures Received by Physicians and Technicians in UF Cardiovascular Laboratory 90 17 Measured Exposure in mR at External Sites of Lead Aprons Worn by Personnel in a Cardiac Catheterization Laboratory 109 18 Weight, Height and Dimensional Characteristics of Phantoms Used in Study 128 19 Location of External Dosimetry Sites on Phantoms and Patients 134 20 Identification of Bone Marrow Dosimetry Sites and Red Bone Marrow Fraction in 15 Subfields of Adult Phantom 139 21 Identification of Bone Marrow Dosimetry Sites and Red Bone Marrow Fraction in 12 S\abfields of Pediatric Phantom,... 142 22 Identification of Vertebrae in the Primary, Transition and Scatter Zones for PA Phantom Exposures 150 23 Normalized Dose Index Values for Adult Phantom 152


LIST OF TABLES Continued TABLE PAGE 24 Normalized Dose Index Value for Child Phantom 154 25 Normalized Dose Index Value for Infant Phantom 156 26 Summary of X-ray Examination Factors Utilized in 304 Cardiac Catheterizations 161 27 Summary of Measured EAP Values in 30 4 Cardiac Catheterizations 154 28 Group I Patient Characteristics 168 29 Procedure Setup and Quantity of Fluoro, Cine and Radiography Used for Group I Examinations 170 30 Group I EAP Values 172 31 Group I Patient TLD Exposure Measurements 174 32 Group II Patient Characteristics 176 33 Procedure Setup, Quantity of Fluoro, Cine and EAP Values for Group II Examinations 173 34 Group II Patient TLD Exposure Measurements 179 35 Estimated Incident Skin Exposure for Group I From EAP Values and Correlation with TLD Site Measurements 181 36 Estimated Incident Skin Exposure for Group II from EAP Values and Correlation with TLD Site Measurements 185 37 Comparison of EAP Values for TLD Monitored Patients with Values from Total Patient Population 187 38 Comparison of Patient and PhantomDerived Dose Indices for Lens of Eye, Thyroid and Scrotum. 189


LIST OF TABLES Continued TABLE PAGE 39 Sioirunary of Exposures Received by Selected Patient Classes During Cardiac Catheterization with Estimations of Selected Dose Indices 193 40 Summary of Patient Radiation Exposure During Cardiac Catheterization Reported by Various Authors 19 6 41 Estimated Patient Exposure Reduction by Use of Pulsed Fluoroscopy and 105 mm Fluorography 213 42 Occupational Dose Limitation Recommendations Suggested by the NCRP 222 Bl Age Distribution for Cardiac Catheterization Patients Less Than 18 Years Old Examined in the UF Cardiovascular Laboratory. 240 B2 Age Distribution for Cardiac Catheterization Patients 18 Years Old or Greater Examined in the University of Florida Cardiovascular Laboratory * 241 B3 Recorded Fluoroscopy Times During Cardiac Catheterization for Adult (A) and Pediatric (P) Patients in the University of Florida Cardiovascular Laboratory 2 43 CI Experimental Calibration Factors for TLD Chips Exposed to Levels of 150 mR to 5000 mR 247 C2 Analysis of Variance for TLD Calibration Points 248 C3 Experimentally Determined Reduction in TLD-100 Sensitivity Read on Eberline TLR-5 and Second Order Polynomial Regression Fit , 249


LIST OF TABLES Continued TABLE PAGE Dl Physician Exposure During Adult Cardiac Catheterization Examinations 252 D2 Physician Exposure During Pediatric Cardiac Catheterization Examinations . . 253 03 Exposure to Technicians in Zone 2 During Pediatric and Adult Cardiac Catheterization Examinations 254 04 Exposure to Technicians in Zone 3 During Pediatric and Adult Cardiac Catheterization Examinations 255 05 Exposure to Technicians in Zones 5, 6 and 7 During Pediatric and Adult Cardiac Catheterization Examinations.. 256 06 Patient and Examination Characteristics Recorded During Personnel Exposure Study 257 07 Summary of Patient and Examination Characteristics During Personnel Exposure Study. 258 D8 Recorded Cine Factors During Personnel Exposure Study 259 09 Analysis of Cine Use During Personnel Exposure Study 260 El Bone and Red Marrow Assignment for Subfields of Adult Rando Phantom 262 E2 Bone and Red Marrow Assignment for Subfields of Pediatric Phantoms 265 E3 Exposure Factors for Adult Phantom Exposures 266 E4 Exposure Factors for Child Phantom Exposures 267


LIST OF TABLES Continued TABLE PAGE E5 Exposure Factors for Infant Phantom Exposures 268 Fl Lateral X-ray Scatter from a 30 x 30 x 22 cm Mix-D Block 273 F2 Integral Dose per EAP . Data Calculated from Values Obtained by Poston and Warner (1974 278


LIST OF FIGURES FIGURE PAGE 1 Dimensional Configuration for Under Table X-ray Source 21 2 Dimensional Configuration for AP Biplane Film Changer. 22 3 Dimensional Configuration for Lateral Biplane Film Changer , 23 4 Distribution of Cardiac Catheterization Patients in the Age Range to 18 Years. 27 5 Distribution of Cardiac Catheterization Patients in the Age Range 20 to 100 Years. 28 6 Mean Fluoroscopic Exposure Time During Cardiac Catheterization Procedures on Patients <18 Years Old 31 7 Mean Fluoroscopic Exposure Time During Cardiac Catheterization Procedures on Patients >^18 Years Old 32 8 Percent Decrease in Sensitivity of Harshaw TLD-100 Chips Read on Eberline Model TLR5 System as a Function of Incident Exposure. 43 9 TLD Dosimeter Package 45 10 Victoreen 555 Calibration Correction Factors as a Function of Half Value Layer. 49 11 Calibration Correction Factors for Victoreen 555 as a Function of X-ray Tiobe Potential. (HVL held constant at 1.25 mm Al Victoreen 555-lOMA chamber used) . 50 12 Block Diagram of PTW Diamentor Exposure Area Product Measurem.ent System. .... 55 13 Setup of Time Delay Relay for Cine Input Signal on Dual Register PTW Exposure Area Product Measurement System 57


LIST OF FIGURES Continued FIGURE PAGE 14 Effect of Backscatter on PTW Exposure Area Product Chainber at Various Phantomto-Charnber Distances 61 15 Identification of TL Dosimeter Sites for Exposure Measurements on Physicians and Technicians 75 16 Room Layout of the UF Cardiovascular Laboratory Showing Work Zones 77 17 Subdivision of Body of X-ray Operational Personnel Wearing Lead Apron With Identification of Active Bone Marrow Fractions 87 18 Isoexposure Contour in Vertical Plane at Side of Table Intercepting Central Axis of X-ray Beam. Adult Phantom, on Flat Table Surface 93 19 Isoexposure Contour in Vertical Plane at Head of Table Intercepting Central Axis of X-ray Beam. Adult Phantom on Flat Table Surface 94 20 Isoexposure Contour in Horizontal Plane at Table Top Height. Adult Phantom on Flat Table Surface 95 21 Isoexposure Contour in Vertical Plane at Side of Tible Intercepting Central Axis of X-ray Beam. Adult Phantom in Rotation Cradle 97 22 Isoexposure Contour in Vertical Plane at Head of Table Intercepting Central Axis of X-ray Beam. Adult Phantom in Rotation Cradle 9 8 23 Isoexposure Contour in Horizontal Plane at Flat Table Surface Height. Adult Phantom in Rotation Cradle 99 24 Isoexposure Contour in Vertical Plane at Side of Table Intercepting Central Axis of X-ray Beam. Adult Phantom in Rotation Cradle with Scatter Shield Added loi


LIST OF FIGURES Continued FIGURE PAGE 25 Isoexposure Contour in Horizontal Plane at Flat Table Surface Height. Adult Phantom in Rotation Cradle with Scatter Shield Added 102 26 Isoexposure Contour in Horizontal Plane 30 cm Above Flat Table Surface. Adult Phantom in Rotation Cradle with Scatter Shield Added 10 3 27 Position of TLD Monitors on External Surface of Protective Lead Apron 10 8 2 8 Wrap-around Lead Protective Apron vrith removable Thyroid Shield 110 29 Alderson Rando Phantom 129 30 Representative Six Month Old Infant Phantom 130 31 Whole Body X-ray of Infant Phantom 131 32 Representative Six Year Old Child Phantom 132 33 Whole Body X-ray of Child Phantom 133 34 Location of External Dosimetry Sites on Phantoms and Patients 135 35 Location of Subfields for the Adult Phantom Model 137 36 Location of Subfields for the Pediatric Phantom Model 141 37 Average Bone Marrov/ Dose per Unit Exposure at Marrow Site 147 38 Idealized Vertebral Bone Marrow Dose Profile for PA Fluoroscopy of Child Phantom 148 Al Indicated mAs for X-ray Tube Potential Settings on Philips "Maximus-100 " Generators Operating in Iso-v/att Falling Load Mode 231 xvi


LIST OF FIGURES Continued FIGURE PAGE A2 Measured Exposure as a Function of Tube Potential for Philips "Maxiinus-10 0" Xray System Operating in Iso-v;att Falling Load Mode . 232 A3 Measured Exposure Rate at Flat Table Surface from Under Table Fluoro/Cine X-ray Tube. 233 A4 Measured Exposure Rate at Surface of Pediatric Restraint Board Positioned on Flat Table Surface from Under Table Fluoro/Cine X-ray Tube. 2 34 A5 Measured Exposure Rate at Cradle Surface from Under Table Fluoro/Cine X-ray Tube. 235 A6 Effect of Backscatter on Surface Exposure Measurement. 237 A7 Variation of Backscatter Factor with Square Field Dimensions and Half Value Thickness 238 Fl Integral Dose per EAP as a Function of X-ray Beam Quality Reported by Carlsson (1963) and Pychlau and Bunde (1965) . 274 F2 Integral Dose per EAP as a Function of Beam Quality Shov/ing Additional Values Obtained from Monte Carlo Calculations of Poston and Warner (1974) 279


Abstract of Dissertation Presented to the Graduate Council of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophv THE RADIOLOGICAL HE7LLTH SIGNIFICANCE OF CARDIOVASCULAR SPECIAL PROCEDURES By William Stuart Properzio June, 19 75 Chairman: Charles E. Roessler Major Department: Environrr^ental Engineering Published information has indicated that radiation exposure to patients and personnel involved v/ith cardiac catheterization procedures is high. A study of the radiation exposure to both groups has been carried out. Variations in exposure levels related to factors such as patient classification, equipment configuration and operational procedures have been investigated. Based on the findings in this study, a comprehensive set of radiological health recommendations are given. Equipment modifications that would allow acquisition of the necessary diagnostic information with less exposure are also proposed. An analysis of tlie personnel monitoring records from ten medical facilities involved with the conduct of cardiac catheterization special procedures showed exposure levels


significantly higher than those reported for diagnostic x-ray workers in general. Exposures at various body sites on the physician and technologists involved with catheterization examinations of pediatric and adult patients were also investigated. The unshielded head and neck regions were seen to receive the highest exposures when compared to the established radiation protection guides for various parts of the body. Physician exposures during studies of acquired heart disease in adults were typically at least twice that received during pediatric congenital defect studies. Annual exposure to a technologist in a facility examining both pediatric and adult patients would be expected to be similar to that of an adult cardiologist involved with a typical yearly case load. The radiation exposure to more than 300 patients undergoing cardiac catheterization for congenital and acquired heart disease have been studied. The incident exposure area product,^, for each patient has been related to multiple surface TLD measurements obtained on a selected subgroup. Adult and pediatric phantoms were used to determine the relationship of incident surface exposure to the resultant dose delivered to specific internal organ systems or parts of the body. These exposure values have been correlated v;ith the examination techniques and equipment used to determine v/here modifications could be made to


reduce these levels. Utilization of pulsed video disk fluoroscopy and 105 mm fluorography may result in reductions of 25 to 60%.


CHAPTER I INTRODUCTION In the last few years, the United States has experienced a drastic increase in the niamber of cardiac catheterization laboratories. The exact number of these facilities is not presently known, but based upon unpublished nanuf acturers sales projections, it may be as high as 600. Wholey (1974) states that it has been estimated that approximately 40 0,00 coronary examinations are being performed in the world yearly. If each laboratory carried out 300 procedures per annum, which is the minimum number of examinations recommended by the Inter-Society Commission for Heart Disease Resources (19 71) required to maintain expertise of the professional team, the number of procedures performed in the U.S. m.ay be as high as 180,000 per year. This is 45% of the v/orld estimate and does not include other acquired valvular, pulmonary, conduction or congenital studies. In a limited number of published studies the radiation exposure to patients and personnel has been shown to be high. Incident exposures in excess of 200 Roentgens (R) have been reported for an individual procedure. The International Comniission on Radiological Protection (ICRP)(1973) has identified this area of radiologic concern. This study was initiated to investigate 1


the radiological health aspects associated with these cardiac special procedures . Cardiac catheterization is an invasive medical diagnostic procedure combining hemodynamic and angiographic techniques . Patient application is found in the evaluation of congenital and acquired heart disease. The evaluation of coronary arterial disease constitutes the largest proportion of the acquired heart disease studies. The procedure is typically performed with single plane fluoroscopy (fluoro) and associated cinef luorography (cine) . The examination will usually consist of a left ventriculargram, and selective coronary angiography. The patient is placed in a rotation cradle to aid in positioning for right and left oblique geometry. Also used is equipment in which the patient position is fixed and the x-ray source and image receptor are rotated on a C-arm. support. The cardiac special procedure room may also be equipped to use rapid film, changers or a 70, 100 or 105 min fluorographic camera. For the study of congenital heart disease, fl^ioro and serial biplane radiography are comm.only used. The patient will usually be positioned on a flat, floating-top table. The. technique of intravascular catheterization can be traced back to Fritz Bleichroder (1912). He passed a catheter from his thigh into the inferior venacava v/ithout fluoro. Werner Frossman (1929) is generally credited with the first individual to pass a catheter into the heart


of a living human subject. At the time of his investigation, Frossman was a 25-year-old German medical student. His concern was to develop a technique whereby drugs could be introduced directly into the heart of patients in severe cardiac distress. Following initial trials on cadavers, he attempted his first investigation on a living subject through selfexperimentation. During his first trial he passed an oiled urethral catheter from an arm puncture site 35 cm into the vein toward his heart. At this point the experiment was aborted due to his colleagues' fear that any further advancement of the catheter might be risky. A week later Frossman made a second attempt v/ith the aid of a nurse. During this trial he advanced the catheter approximately 65 cm under fluoroscopic observation from a left elbov/ venasection. He then walked, with the catheter in place, to the hospital radiology department so a radiograph could be taken to verify the placement of the catheter in the right heart chamber. Frossman described the utilization of this technique in a patient suffering from a perforated appendix (Sourkes, 1966) The patient subsequently died, but he states that the effect of the catheter, which had been left in place for approximately 5-1/2 hours, v/as not the cause. Following hi.s initial investigation the technique of heart catheterization was not put to any general use until 19 40 V7hen Andre Cournard and Dickerson Richards utilized it in their research studies relating to the physiology of the


heart (Cournard and Ranges, 1941). The impact of this research, using heart catheterization techniques, resulted in their receipt of the 1956 Nobel Prize for medicine and physiology. Frossman was also included as a co-recipient of the award due to his initial work. The use of heart catheterization techniques for applied clinical investigations dates back less than 20 years. Dexter and colleagues (19 47) was one of the first to report on its use in the study of congenital heart defect studies. Until 1950, investigations had been limdted to the right heart. Zimmerman and colleagues (19 50) described a retrograde technique whereby the catheter was advanced into the left heart via an artery over the aortic arch. The alternate technique of trans-septal puncture in which the catheter is passed through the septal v;all of the heart to gain access to the left heart chambers was described by Ross (1959) and Cope (19 59) . One of the prim.ary uses of cardiac catheterization techniques today is in the study of acquired heart disease. The work of Sones and colleagues (19 59) in the development of cine angiographic procedux-es opened the door to selective coronary studies in common use today. In the so-called Sones technique, the catheter is introduced into a brachial artery after it has been surgically isolated. Using the percutaneous puncture technique described by Seldinger (19 5 3) , Ricketts and Abrams (1962) described an alternative procedure where the catheter is introduced into a femoral artery in the groin.


Judkins (19 6 7) has further developed this percutaneous technique in combination v/ith the use of preshaped catheters for selective coronary artery studies. Objectives of Study Recognizing the potential high exposure levels that exist during cardiac catheterizations, an evaluation of the radiological health significance of these procedures was undertaken. The specific objectives of the study were as follows : 1. Identify key factors relating to equipment, clinical personnel and procedures currently found in a cross-section of cardiovascular special procedure facilities . 2. Measure patient and operator exposure and evaluate the magnitude of these levels in terms of the doses delivered to selected organ systems or regions of the body. 3. Develop and evaluate equipment and procedural changes that would result in a reduction of unnecessary radiation exposure. 4. Develop guidelines for the radiological evaluation and operation of a cardiovascular x-ray special procedure facility. The above objectives were achieved by (1) conducting a field survey to provide insight into the range of current practices


and (2) performing an in-depth study in the cardiovascular laboratory of the Shands Teaching Hospital of the University of Florida (UF cardiovascular laboratory) . The radiological health aspects were, for the most part, divided into the two broad areas of patient and operator exposure.


CHAPTER II CARDIOVASCULAR X-RAY PRACTICES A general overview of the range of cardiovascular laboratory organization and practices was obtained through a field survey of selected facilities within the State of Florida. In addition, more specific information on a single laboratory was obtained in the initial stages of the in-depth investigations carried out in the UF cardiovascular laboratory. Nine Florida Facilities The exposures to patients and personnel during cardiovascular special procedures would be expected to vary from facility to facility. Factors such as equipment setup and operational characteristics, patient classification and procedural techniques might be expected to be of key importance. To investigate the variations that exist among facilities, a field survey of ten cardiac catheterization laboratories in nine Florida hospitals was conducted. The surveys v/ere conducted in cooperation with the Radiological Health Section of the Florida Division of Health and one or more representeitives from that agency were present during each field visit.


The results of the field survey have been broken down into the areas of facility operational structure, personnel staffing, x-ray equipment and radiological health procedures. Table 1 gives a breakdov/n of the organizational and operational characteristics of the nine facilities. Two were part of a department of radiology and a third, although structurally separated from radiology, was operated under the direct supervision of a radiologist. The remaining six facilities were administratively structured within departments of cardiology. Four of the facilities had been operating for five years or m.ore while the remaining five laboratories were about one year old. Although the number of facilities was limited and selection had not been based on statistical considerations, the general trend regarding the expansion of new cardiac catheterization laboratories on a nationwide basis seems to be borne out by the n\imber of new facilities in this sample. In tv/o-thirds of the facilities, only cardiac studies were performed. For the remaining three, additional noncardiac special procedures v/ere carried out in the room. In each case, these additional studies were conducted by an alternate group of physicians on a second priority basis . Table 2 gives a breakdov/n of the personnel associated with each laboratory. In the majority of the cardiac catheterization laboratories, a cardiologist alone v/as responsible for operation of the facility. In the two


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12 laboratories where radiologists were involved, they acted as technical directors, and cardiologists were still primarily responsible during patient examination. In addition, they were available for consultation with and often assisted the cardiologist during the angiographic portions of a study. The technical support staff were predominantly cardiovascular technologists. This is a relatively new medical technology specialty, but due to an active junior college training program at one location in Florida, a number of graduates have been made available to the laboratories visited in this survey. Better than one-half of the facilities were found to have no x-ray technologist and four had neither a radiologist nor an x-ray technologist. The input of a radiation or health physicist was also seen to be minor. Of the two facilities that are listed as having the input of such an individual, the first was the hospital safety officer v/ho admitted his only involvement v/as in followup studies when high film badge readings v/ere obtained. The participation at the second laboratory related to the author's activity at the University of Florida as a graduate student. Table 3 gives a brief outline of the x-ray equipment setup in the nine facilities (note that facility number six v/as equipped v/ith two separate special procedure rooms) . The x-ray generators represented three manufacturers. Nine of the procedure rooms v/ere equipped to perform single plane fluoro/cine (facility number four had two im.age intensif iers ,


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15 but a single fluoro/cine x-ray source) . For the one facility that had the capability to perform biplane cine, they stated that it was infrequently used at the current time. All facilities were equipped v;ith serial film changers; 70% were capable of simultaneous biplane exposures. Only two of the rooms were equipped with fluorographic cameras and neither was used during cardiac procedures. All facilities v/ere equipped with some type of patient rotation cradle. In onehalf of the cases this device was an add-on cradle that elevated the patient above a lower flat table surface. Table 4 lists a number of items directly relating to radiation safety. Seven of the laboratories had been previously inspected by the State and/or an in-house or outside consultant. Two facilities had not been previously inspected, but both had been in operation for only approximately one year. No determination of the content or adequacy of the prior inspections was attempted. The number of protective aprons available at each facility was consistent with the number of individuals involved with a procedure. Apron design and lead equivalence varied. A number of situations were noted where a technician indicated that he positioned a non-wrap-around apron on his back since the greatest anticipated exposure v/ould result when he was standing with his back to the patient. In most cases the aprons were stored in the procedure room. At one facility an individual entering the room after a procedure


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18 had started would have to walk past the procedure table to select an apron. A shielded control booth was present in all but one room, but the physiological raonitor controls were located in the room in close proximity to the procedure table in six out of ten cases . The personnel radiation monitoring procedures varied from facility to facility. A discussion of the type and position of the monitoring device and records of the exposures received are discussed in Chapter IV. Briefly, it can be stated that badge sites outside and under the protective lead apron were used. In a number of situations no firm policy regarding the badge site existed with the decision as to site being left up to the individual. In only two of the nine facilities were more than one monitor per person used. In one facility an organized rotation of technical support personnel existed. Although the primary purpose was to give experience in all aspects of the procedure to the staff, a distribution of exposure was also achieved. Three other facilities indicated some rotation occurred, but in 50% of the cases each person had a non-varying job assignment. In general, no policy v/as follov/ed to position nonessential individuals at sites away from, the patient during cine exposures. Of the five facilities that utilized serial


19 radiographic techniques on a regular basis, the physician remained next to the patient during serial radiography and was often assisted by one or more technicians. University of Florida Cardiovascular Laboratory The following discussion reports conditions in the UF cardiovascular laboratory at the time of the study. Equipm.ent This room was used to study both adult and pediatric patients. The room was equipped with two Philips^ "Maximus100" x-ray generators. An under table x-ray source with over table image intensifier used for fluoro and cine exposures. The cine camera was a 35 mm unit which operated at frame rates up to 6 4 frames per second. Two ceiling mounted radiographic tubes v/ere used in conjunction with biplane Elema Schonandert* cut film serial changers. The x-ray generators were three-phase units. The maximum tube potential for radiographic exposures was 150 kVp. During radiographic operation, the generators utilized the falling load principle. This falling load, or isowatt principle, which has been described by Van de Wetering (19 71) , achieves the tube loading for any specified setting ^Philips Medical Systems, Inc., Shelton, Connecticut. ^Elema Schonander, Inc., Elk Grove Village, Illinois.


20 of tube potential and exposure time. During the exposure, tube current is initiated at a high value so that the maximum rated anode temperature is quickly achieved. Tube current is subsequently reduced by m.eans of a motor-operated variable resistor in the primary filament circuit. The advantage of this system is that the desired exposure in the minimum exposure period is automatically achieved without the need to reference the tube rating charts. During fluoro the x-ray system, is operated in a single phase m.ode with a maximum tube potential of 110 kVp. The procedure taJole had a flat floating top that allowed longitudinal and lateral movement. For pediatric congenital heart studies, the patient was strapped to a restraint board constructed from 0.64 cm (0.25 inch) fiber board covered with a foam pad. Adult patients v;ere usually examined in an addon rotation cradle. Figures 1 through 3 show the geometric arrangements for the under table fluoro cine tube and the two biplane radiographic sources. The measured half value layer (HVL) values for the x-ray tubes and examination conditions are listed in Table 5. During this study, two image intensifiers v/ere alternately installed in the system. Both intensifiers had a cesium iodine (Csl) input phosphor. One tube was a single mode intensifier and the second a dual mode; they were described by the manufacturer as a six inch and nine inch, respectively. The visible area measured at the input


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23 u u a (U (0 nJ O fC d


24 TABLE 5 Measured First Half Value Layer for Various X-ray Source and Patient Geometries X-ray Tube Measured KVL^ at 80 kVp and Geometry Identification (mm Al) Vertical, PA, radiographic source (Machlett "Dynamax" 69B) 3.3 plus flat table surface 4.2 plus flat table surface and pediatric restraint board 4.4 plus flat table surface and cradle 4.5 Horizontal, LAT , radiographic source (Machlett "Dynamax" 64B) 3.1 Under table fluoro/cine source (Philips grid controlled) plus flat table surface 4.4 plus flat table surface and pediatric board 4.7 plus flat table surface and cradle 4.9 All values measured v/ith PTV?. exposure area product chamber attached to diagnostic source assembly.


25 2 phosphor of the single mode tube was 156 cm (diam.eter of 14.1 cm) and for the dual mode tube 143 cm'^ (diameter 13.5 cm) and 29 6 cm" (diameter 19,4 cm.) . A 60 line 6:1 grid was used with both intensif iers . A 35 mjn cine camera, normally operated at 64 frames per second, was used in conjunction with both intensif iers . The biplane film changers utilized 14 x 14 inch cut film and had a maxinum. rating of six films per second. The changer magazine would accept 30 films so the maximum number of films exposed in a biplane angiographic run v/as limited to 60 films. The lateral changer was equipped with an 80 line criss-cross grid and the under table anterior-posterior (AP) changer v/ith an 80 line 12:1 focused grid. The position of the film with respect to the input grid surface for each film changer is shown in Figures 1 and 2. The fluoro/cine system was equipped v;ith an automatic brightness control system. The brightness of the output phosphor of the image intensifier was monitored by a phototube. The signal from this photo-tube detector was then compared with a pre-set reference value. The output of the x-ray tube was then autom.atically varied until the monitored and reference signals matched. The brightness control system used with the single-miode tube was a current modulation system. For the dual-m.ode intensifier tiobe, potential was varied to maintain the desired brightness level.


26 Appendix A gives characteristic data for operation of the isowatt falling load system. Measured exposure output data for radiographic and fluoro operations are also given. Patient and Examination Trends The cardiac catheterization records at the Shands Teaching Hospital of the University of Florida were reviev/ed to extract information regarding patient age, frequency of repeat examinations and fluoro time. A tabular listing of the patient age and fluoro time is given in Appendix B. Figure 4 shows a plot of the age distribution for catheterization patients less than 18-years old. This group consists primarily of patients evaluated for suspected congenital heart defects. The histogram shows a bimodal distribution with a large peak in the birth to 6-month period and a second at 5 to 6-years . Fifty percent of the catheterizations on patients less than 18-years old were conducted on individuals less than 4-years old. Data for the adult patient studies are shown in Figure 5. Fifty-one percent of these studies were carried out on patients in the 40 to 60 age period. Table 6 lists the frequency rate of cardiac catheterization on a per patient basis. Approximately l/4th of the pediatric patients received multiple catheterizations. The maxim-um number of these repeat procedures was six. For the adult patient, only 15% were examined more than once. The maximum number of multiple examinations was found to be five


27 30 20 10 ... i 1 fmrnmh-h: I i — i i I i I J — r 10 15 20 AGE IN YEARS Figure 4. Distribution of Cardiac Catheterization Patients in the Age Range to 18 Years.


28 15 10 5 ... 4V 20 40 60 80 AGE IN YEARS 100 Figure 5. Distribution of Cardiac Catheterization Patients in the Age Range 20 to 100 Years.


29 c


30 for one individual. Patients seen in a large teaching hospital typically consist of second party referrals. The referral is often made on the basis of a complex or out-ofthe-ordinary diagnosis. This factor might be expected to have some bearing on the examination frequency. In the case of the referral patient, the probability that a prior catheterization had been performed would be expected to be significant. No attempt was made to establish the contribution from heart catheterization examinations at other institutions . Figures 6 and 7 show average fluoro times for pediatric and adult patients studied over a 12-year period. The data points represent the one-month mean for the third and ninth months of the respective years. For 19 73 and 19 74, data for each month are shown. Although the conduct of a congenital heart study in children differs from the acquired heart disease evaluation in an adult, the m.ean fluoro times are seen to be quite similar. Mean values of approximately 15 minutes per procedure were observed during 19 6 3 and had increased to the lov7 tv/enties by 19 73. The increase may be associated with the added complexity and amount of information obtained from the catheterization procedure over this time period. Starting in late 1973 a consistent decrease in fluoro times for pediatric patient studies can be observed. During this period no significant changes in staff or examination


31 o o r« ? o » o I o ^ -H Eh a) • P rH tn o O H, m X M CD O >H •H O rH O V w O W M -p O C 3 (1) t< -p

32 -^ \o u 'a CO O O H (0 -H euro OrH. D a| O M o c 3 0) Pm -P J' (UTIU) awiJL aHnsodxa Didoosoaonu


33 techniques were made. The decrease may be associated with an increased awareness of potential radiation hazards on the part of the physician since the decrease directly parallels the initiation of this study. No similar change in the mean fluoro times for the adult examinations was observed.


CHAPTER III RADIATION MEASUPJ^I'lENT EQUIPMENT AND TECHNIQUES The same radiation measurement equipm.ent was used for studies of both personnel and patient exposure. A thermoluminescent dosimeter (TLD) system, was used for personnel, patient and phantom monitoring. The various x-ray sources were equipped with transmission ionization chamber systems which measured beam area integrated output as an index of the total incident energy delivered to the patient. In addition, a free air calibrated ionization chamber system. was used as a reference instrument for calibration of the other systems and for selected beam intensity measurem.ents . Therm.olum.inescent Dosimetry Thermoluminescent dosim^etry technique has been used extensively in this study. For the assessment of doses associated v/ith diagnostic x-ray procedures TLD offers a niimber of advantages when compared to alternate techniques, such as film or ionization methods. The dynamic range for TLD ' s is large, extending over a range from, lovz mR values to thousands of R. The size of the crystal dosimeters is sm.all compared to ionization chambers or film, thus introducing minimum problems v/hen placed on patients or personnel. One 34


35 of the major disadvantages of using film dosimetry is the large energy dependence of the emulsion in the diagnostic energy region. In comparison, a TL phosphor, such as lithium fluoride (LiF) , shows very little change in sensitivity in this energy region. The utilization of TLD as a radiation dosimetry technique involves the quantification of light emitted from a heated crystal that was previously exposed to ionizing radiation. Becker (19 73) points out that of approximately 3,00Q natural minerals, over three-quarters exhibit this effect. The basic physical principle is associated with the elevation of electrons from the valence band to the conduction band when exposed to radiation. The freed electron and associated hole move through the crystal and may recombine or be trapped at a lattice defect or impurity site. When the crystal is subsequently heated, the electron or hole can be released from the metastable trap and return to its ground state. During this readjustment in energy states, a light photon will be emitted. The quantitative relationship between the thermally stimulated luminescence and the previous exposure facilitates its use as a radiation dosimeter. Harshav/ LiF TLD-100 was the particular phosphor used. The material v/as in the form of 0.32 x 0.32 x 0.09 cm (1/8 X 1/8 X 0.0 35 inch) chips. This particular phosphor is Harshaw Chemical Company, Solon, Ohio


36 presently the most widely utilized TLD material and the one for which the greatest amount of p\:!blished information exists. It is well suited for x-ray dosimetry in the diagnostic x-ray range. The energy response of TLD-100 is relatively independent of photon energy. However, it does have an increase in sensitivity for photon energies of less than 100 keV effective and is approximately 30% m.ore sensitive at an effective energy of 25 keV than at ^^Co energies (Cameron et al., 1963). Harshav; states the effective atomic numloer of LiF TLD-100 for photoelectric absorption is 8.2. This value is close to that of tissue (7.42) and air (7.6 4) . From a dosimetry standpoint this means that the phosphor's response could be considered approximately air or tissue equivalent. Due to the sm^all difference in the effective atomic numbers of LiF and tissue, the chips cannot be seen in a diagnostic x-ray image v/hen positioned on the body of a patient. Thus, the possibility of confusion or misdiagnosis introduced by a dosimeter(s) being interpreted as clinical anatomy in the im.age is eliminated. Harshaw TLD-100 contains a mixture of Li and Li in their natural isotopic ratio of 7.5 to 9 2.5% respectively. The crystal matrix also contains some im.purities . Becker (19 73) states that although the identity and amoun.t of these impurities have not been officially disclosed by the manufacturer, those of dosimetric importance are thought to be magnesium (I4g) and titanium. (Ti) . Edelmann (1967) has shovm


37 that the addition of 0.0013 mole percent of Mg to pure LiF produces a maximum increase in sensitivity for this activator impurity. Becker and colleagues (19 70) have carried out spectral chemical analysis of TLD-100. Based upon this v/ork, Becker states that the probable concentration of Ti is 0.001 mole percent. It is also possible that\jm. (Al) and/or cadmium (Cd) , which were also shov/n to be present in the TLD-100, may play a role as activator or co-activator. The TLD chips were read on an Eberline'^ model TLR-5 system with nitrogen flow. This system employs a low temperature dump during which the chip to be read is heated to a pre-selected temperature sufficient to release the lov; tem.perature peaks. During this dump portion of the readout the counter is not gated on. The chip is then elevated to the readout temperature and the reader registers the counts under the major photopeak. For use v/ith the TLD-10 chips the unit v/as adjusted for the dur^p and read cycles as follows: 140°C for six seconds followed by 250°C for 12 seconds . For dosimetry measurements, the TLD chips were arranged in sensitivity-selected pairs follov/ing the procedure suggested by Gooden and Bricker (19 72). Three hundred virgin chips were obtained for use in this project. These chips ^Eberline Instrument Company, Santa Fe , Nev/ Mexico.


38 ware first arbitrarily divided into three groups of 100 chips each. Each group was then simultaneously exposed to a knov/n exposure level and read out. This procedure v/as repeated three times so that an average sensitivity for each chip could be obtained. Each group of chips was annealed prior to the first exposure and between each subsequent exposure following the procedure to be described belov/. During the exposure each chip was placed in a numbered gelatin capsule so that its identity could be maintained. The average reading for the three exposures was then calculated for each chip. Within each group of 100, the chips were then ranked according to sensitivity. The sensitivity grouping procedure consisted of first pairing the least and most sensitive chips and sequentially working toward the center chips in the ranking scheme. Once the sensitivity selecting procedure was completed, each group of 50 dosimeter pairs v/as utilized individually. A calibration factor for each group v;as determined whenever that group was utilized. When any chip pair within a particular group required annealing, all pairs in the group were included. This procedure was followed so that any changes in sensitivity resulting from the annealing procedure would be equalized in all chips in a particular group. The annealing procedure utilized was that suggested by Harshav;. It consisted of one hour at 400 °C follov/ed by two hours at 100 °C. The chips were positioned on a


39 pre-numbered brass plate. Two ovens were used so that close teraperature control could be n^aintained. The six-second lov/ temperature dump in the TLR-5 readout cycle is intended to remove the low temperature peaks. However, where dosim.eter pair exposures within a specific group of chips may range from lev/ mR to R values , the possibility that the lov/ tem^perature peaks may not be equally removed during the sixsecond reader dump would be a major source of error. To minimize the possibility of this source of error a post-exposure pre-reading annealing at 100 °C for ten minutes was also carried out as recommended by Harshav/. The 100° C for ten minutes' annealing v/as carried out by placing the chip pairs in a 6 x 50 mm Pyrex culture tube. Multiple tubes were then placed in a pre-numbered lucite support grid and suspended in boiling v/ater for the specified time period. With continued use, the sensitivity of a group of TLD chips might be expected to change. Due to an effect seemingly similar to that causing supra-linearity , an increase in sensitivity in TLD-100 follov/ing previous exposures has been reported by Cameron and colleagues (19 6 8) . The increase in sensitivity was noted to be as great as a factor of six for an annealing cycle utilizing a high temperature of 280°C for one-half hour. The effect v/as minimal for a 400 °C, one-hour annealing cycle. For periods of greater than one hour at 400°C, a decrease in sensitivity. by as much as 20% from its


40 original value was noted. A change in sensitivity might also be expected due to cracks or chips in the crystal dosimeters. The accumulation of dirt on the chips would be expected to reduce the sensitivity since a smaller portion of the light would be able to escape and be counted by the photomultiplier tube. Another factor of major importance in this study has been the day-to-day variation of the TLD reader. To account for these factors that can affect sensitivity, a calibration was performed each time a group of chip pairs was used. Calibration exposures were carried out utilizing a Siemens 250 kVp x-ray therapy unit. The unit was operated at an indicated 80 kVp with a source-to-dosimeter distance of 150 cm. The measured HVL of the beam was 4.1 mm of Al with all added filtration removed. This is in reasonable agreement with the HVL reported for the various tubes used on the diagnostic x-ray system. The beam v/as adjusted to a 10 x 10 cm field at the 150 cm source-to-chip distance. The chips were supported on a thin sheet of paper 30 cm from the floor. At this distance the effect of backscatter is negligible. A Victoreen 555-lr4A probe v;as positioned simultaneously in the beam with the chips to determine the delivered exposure. From a 50 chip pairs group, ten chip pairs typically would be set aside for calibration. Two chip pairs would be unexposed and used as background controls. Tv/o pairs each


41 would then be exposed to exposure levels in the range from 150 mR to 5.5 R. The calibration factor could then be obtained from the niimerical average or the slope of the straight line drawn through a plot of TL units versus exposure. Linearity of Calibration Factor v/ith Exposure Level The Eberline TLR-5 reader has a high and low sensitivity setting (low and high range respectively) . For the chips used in this study and read on the Eberline system operating in the high sensitivity range, a calibration factor of 4.5 TL units per raR would be typical. The reader has a fivedigit decimal display v;ith a resultant maximum counting capacity of 10-^-1. This means that for a chip exposed to greater than 22.2 R, the reader v/ould be expected to exceed its maximum counting capacity and recycle through zero. The operator has tv;o options when reading a chip exposed to a suspected exposure level greater than this limit. He can switch to the lov7 sensitivity range or m.anually observe the number of times the counter cycles through zero. VJhen the system is sv/itched from^ high to low sensitivity, the voltage on the photomultiplier is lowered. Trial readings made after sv;itching ranges dem.onstrated that a period of 12 to 2 4 hours 'was required for the system to stabilize following such a change. Due to this unreasonable stabilization period and the fact that additional calibration chips would be required v/hen using both sensitivity


42 ranges, the system was operated in the high sensitivity (low range) position only. To evaluate the response of the dosimetry system, calibration exposures were made over a range up to 100 R. Two chip pairs were exposed at each calibration point. An average calibration factor for each point v.^as determined. A second order polynomial least square fit of tliese data was calculated. A plot of these data as percent decrease in intensity from the values measured at 5 R or less versus exposure is given in Figure 8. The curve shows the decrease in sensitivity for exposure values greater than 6 R. This effect is felt to be due to the reader since the response of TLD-100 has been shown to be linear V7ith exposure for values to approximately 10 R (Eggermont et al., 1971). At this level a supralinear effect is observed which increases the dosimeter response. Calibration exposures were made over the range of 150 mR to 5.5 R. In calculating the calibration factor, it was assumed that the calibration factor had a flat response over the range used. To check this assumption, the experimental data for nine calibration runs were statistically analyzed. An analysis of variance v/as carried out by separating the data into nine blocks v/ith four exposure level treatments for each block. The nominal treatments v.'ere 150, 550, 2000 and 5500 mR respectively. The experimental data and analysis of variance tables are shov;n in Appendix C. The calculated F


43 x:


44 statistic for the treatments (different exposure levels) was not significant to indicate there was departure from linearity over this exposure range. By comparison, the variation between calibration runs is seen to be significant. This is consistent v/ith the expeched variation of factors previously discussed and establishes the requirement to run a calibration point for each use of a particular paired group of chips Dosimeter Packa ge The TLD chips used in the measurement of patient and operator exposure were sealed in polyethylene packages. The chips were first sandwiched between a fold of black art construction paper. This protected the chips from light (ultraviolet) exposures that can affect chip readings. The enclosed chips were then positioned between the polyethylene and the edges fused with a heat-sealing device. The sealed package was air and water tight and could be sterilized by emersion in a liquid solution, if required. The dimensions of the completed dosimeter packages were approximately 1.5 x 1.5 cm. Figure 9 shows an exploded view of the packaging. The International Commission on Radiation Units and Measurements (ICRU) (1962) presents graphical data relating to the required thickness of unit density material required to establish electron equilibrium as a function of photon energy. For the minimum energy of 100 keV given by the ICRU, the density thickness of build up material required is approximately 0.015 g/cm^ . The density thickness of the


45 polyethylene and paper surrounding the TLD chips was found to be 0.0216 g/cm^ . This is in reasonable agreement with the ICRU value for x-ray photons in the diagnostic energy region. Exploded view Sealed dosimeter Polyethylene Black paper with TLD chips Heat sealed edges Figure 9. TLD Dosimeter Package.


46 Victoreen 555 System A Victoreen model 555 Radocon II integrating ratemeter v/as used as the primary dosimetry reference instrument for radiation measurements performed in this study. Victoreen states that the precision of the model 555, operating in the integrate mode, is + 1% for all scale ranges except the 30 mR range. For this most sensitive scale, the precision is + 2%. For long term, operation (over a period of 90 days or greater) these values must be increased by + 0.2%. In the rate mode the precision is + 2% for all except the most sensitive scale for which the value is + 4%. The long term precision for the rate mode of operation m.ust be increased by + 1% for periods greater than 9 days. The chamber calibration inaccuracy for the 555-0. II^LA, 555-lMA and 555-lOMA probes is given as + 5% over the energy range of 30 to 400 keV effective. These three chambers (serial numbers 170, 225 and 262 respectively) were calibrated at the Bureau of Radiological Health, U.S. Department of Health, Education and Welfare using a Victoreen model 481 free air ionization chamber. This free air system has a stated accuracy of + 0.5% over its operational range. The calibration data are given in Table 7 and the calibration Victoreen Instrument Division, Cleveland, Ohio


47 Cr^ C C C C C (U C -H -H -H -H -H Cn-H I E e E e g pc; (1) j en c -P D^ 0) 0:1 m


48 correction factors are plotted as a function of the HVL in Figure 10 . Since the first HVL is not a unique description of the quality of a continuous x-ray spectra, the validity of plotting the correction factor as a function of this index was checked by calibrating a 555-10r4A chamber with the HVL held constant (Morgan and Fewell, 19 73) . The results of this evaluation are shown in Figure 11. For the calibration points from 70 to 100 kVcp, the experimental calibration factors are seen to vary by 2.6% of the mean. This variation is generally consistent with the stated precision of the 555 system v/hen operated in the integrate mode. The random nature of the calibration points in this energy range may indicate that a straight line can be drawn through the mean value. If this mean value is extended as a smooth curve through the lov/er energy calibration points, the chamber seems to have a flat response (to 2.6%) for a constant HVL of 1.25 mm Al over the kVcp range of 50 to 100. No calibration values for operation at kVcp value greater than 100 are given due to operational limits on the free air ionization chamber. If the calibration had been carried out for a higher HVL, such as 3 to 4 rvsn of Al consistent v/ith the values for the diagnostic tubes used in this study, the calibration factor v;ould be expected to vary even less due to the reduction of the lov/er energy components of the x-ray spectrum.


49 1.3 -1.2 1.1 1.0 't integrate mode -At ''': A— Rate mode O.IMA Chamber (SN 170) 1.3 1.2 _. 1.1 1.0 r^ IMA Chamber (SN 225) 1.3 1.2 1.1 .1.0 .. ft lOMA Chamber (SN 262) 1 h 2 4 HALF VALUE LAYER, mm Al Figure 10, Victoreen 555 Calibration Correction Factors as a Function of Half Value Layer.


50 1.2 -1.1 1.0 0.9 -0.8 0.7 Tube Potential (kVcp) 30 40 50 70 80 90 100 Correction


51 Exposure Area Product Measurement In many situations it is desirable to know the exposure, dose or some other index, such as integral dose, received by a patient undergoing a diagnostic x-ray examination. The exposure at any specified point, such as the incident skin surface, is a complex function of a multitude of factors including t^±>e potential and v^ave form, tube current and time of exposure, filtration, source-to-patient distance and field size. If the dose delivered to a specific body site or organ system is desired, additional factors must be considered. Calibration data for a particular x-ray unit can be obtained for its various operating conditions to allov/ determination of the resiTltant patient exposure if all the variables for a particular examination are recorded. This requirement to obtain and record all of the variables associated v/ith each individual exposure can be time consuming. In the case of special procedure vrork where multiple modes of viewing and recording such as fluoro, cine and/or radiography may be employed, the recording task becomes nearly impossible to perform. A number of authors have described the use of x-ray monitors attached to the x-ray unit to directly measure incident energy. Feddema and Oosterkamp (19 53) measured the product of beam area and irradiation time during fluoro. They attached a watt-hour m:eter to the x-ray unit and modulated its reading by a connection to the adjustable diaphragm


52 of the x-ray unit via potentiometers and cog wheels. Morgan (19 61) described an incident-energy monitor which used a twocompartment ethanefilled ionization chamber. The monitor was designed to give a chamber response relatively independent of radiation quality for a HVL range extending from 0.5 mm Al to 10 mm of Al. Reinsraa (1962) utilized an ionization chamber designed so that its spectral response was reasonably independent of the quality of radiation over the usual diagnostic range. This unit, marketed as the Philips Diagnostic Monitor, was attached directly over the exit port of the collimator. The measurement chamber was not transparent to light and thus had to be physically moved when it was necessary to use the collimator light localization system. An alternate approach has been the development of instruments that measure the exposure or exposure area product (EAP) . Airth (19 59) v/as one of the first to report such a system. His unit consisted of an ionization chamber built into a fixed rectangular beam-defining cone. The unit was calibrated to read in units of R exposure at the patient skin surface. Arnal and Pychlau (1962) and Carlsson (1965) have described "pancake" type ionization chambers that are positioned on the distal port of the beam limitation system. The chamber is larger than the m.aximum dimensions of the beam and, therefore, will measure the EAP. The Arnal and Pychlau system, with a transparent 0.5 mm Al equivalent ionization chamber, is currently manufactured by Physikalisch-Technische


53 Werkstatten (PTW) of Freiburg, West Germany and known as the "Diamentor" . Ardran and Crooks (1963, 1965) have evaluated the Philips Diagnostic Monitor and two models of the PTW Diamentor. The Diamentors tested were those utilizing the opaque 2.0 mm Al equivalent ionization chamber and the transparent 0.5 mm Al equivalent unit (Arnal and Pychlau, 1962). They state that the Philips unit, v/hich reads in terms of incident energy, is difficult to calibrate since no applicable direct measurement method exists. It is their opinion that since it is currently impossible to judge the biological effect of a delivered diagnostic dose level to a large area of the body, as opposed to the same dose over a single or small number of areas of the body, the refinement necessary to develop an instrument that will read directly in energy units is unnecessary. The incident energy is also not equivalent to integral absorbed dose. Correction for backscatter, lateral scatter and transmitted energy must be made and can account for variations up to a factor of two (Carlsson, 1963) . Instrumentation of X-ray Unit For the purpose of this study, the under table x-ray source (for fluoro/cine) and the two ceiling-mounted tubes (for biplane radiography) in the UF cardiovascular laboratory were equipped with EAP meters. These m.easurement systems.


54 manufactured by PTW , ^ use a 0.5 mm Al equivalent lighttransparent ionization chamber and remote digital readout. Individual measurement systems were installed on the tvzo radiographic sources and the under table fluoro/cine tube. The readout for the fluoro/cine chamber had a dual register so that the fluoro and cine signals could be registered separately. Figure 12 shows a block diagram of the PTW system. The light-transparent ionization chamber is attached across the exit port of the x-ray beam-limiting device. The chamber is connected to the preamplifier and control unit by a 18 meter triaxial cable. The preamplifier and control modules were located in the shielded control booth of the special procedure room. During radiographic and cine exposures, the signal from the ionization chamber can exceed the input rate of the control readout module. When this occurs, the input signal is shunted to a storage capacitor in the preamplifier section. This signal is s\absequently gated through a constant-current resistor into the control module. In practice, this phenomenon can be observed in a continued count registration by the readout system following termination of the exposure. This creates no problem with the biplane radiography since ^Distributed in U.S. by Nuclear Associates, Westbury, New York.


55 Diagnostic source assembly (TU Preamplifier and gate Control 1 r 18 meter cable Measurement chamber I 1 1 T i 1 1}^ J S storage capacitor W Electronic switch L Constant current resistor K Flip-flop (ADC) R Feedback N Power supply Z Register I Pulse shaper Figure 12. Block Diagram of PTW Diamentor Exposure Area Product Measurement System.


56 each radiographic tube was instrumented with individual ionization chamber and readout system. For the under table fluoro/cine tx±)e, v;here one chamber was used V7ith a dual register readout, a 220 volt signal from the primary cine contactor in the x-ray control was used to activate a relay gate in the dual register EAP control. This allowed automatic separation of the exposure signals resulting from fluoro and cine. Since the cine signal would often exceed the input count rate of the measurement system., a time delay relay was added. This modification, shown in Figure 13, allowed the counter to remain in the cine mode for a predetermined time follov/ing termination of the exposure. The variable time delay relay allov/ed a delay period of to 10 sec. A setting of 5 sec was found to be adequate to register the maximum exposures that might occur for the large adult patient. Exposure Area Product Meter Calibration The EAP meters were calibrated follov/ing installation and at periodic intervals. The calibration procedure involves first measuring the beam size at a predetermined position. X-ray film or Kodak Linograph direct print paper can be used for this field size measurement. A calibrated ionization chamber is then positioned at the same position for which the field size was determined. This measurement position is not critical, but should be at a sufficient distance from the


57 Time delay relay 220 Volts 60 Hertz ^. I To cipxe contactor 115 Volts 60 Hertz Q o r -'W^

58 table top or other support surface to minimize the effect of backscatter. An x-ray exposure is then made and the calibration factor determined as follows: EAP Calibration Factor 2 (Measured R) (beam size, cm ) EAP meter reading Due to the nature of the analog-to-digital converter (ADC) used in the PTV7 meter, a maximum uncertainty of up to one count can exist. This results V7hen a signal almost sufficient to trigger the ADC flip-flop circuit has been collected, To minimize this possible error, at least 75 counts should be registered on the EAP meter. This will reduce this source of error to no greater than 1.3?;. All calibrations were carried out at an indicated tube potential of 80 kVp. This value represents a typical operating potential. The beam size v/as adjusted to approximately a 10 x 10 cm field. Sources of error for the EAP system when operating at other technique factors, beam size and setup geometry will be outlined below. V7ith the patient in the cradle, the beam, at the patient entrance surface will be attenuated and a correction factor must be applied to the fluoro/cine EAP calibration factor. Experimental data at 80 kVp indicate that the EAP meter calibration for this setup rust be multiplied by 0.66.


59 Effect of backscatter Ardran and Crooks (19 63,1965) measured the effect of backscatter on two PTW measurement chambers, a light opaque 2 mm Al equivalent chamber and a 0.5 mm Al equivalent transparent unit similar to the ones used in this study. In their investigation, the chambers were positioned 30 cm from, the x-ray focal spot. The beam size v/as fixed so that a 40 x 40 cm field at a source-to-field distance of 100 cm vras obtained. A 12 X 12 X 8 inch Mix-D phantom v/as then exposed at various phantomchamber separation distances. The effect of backscatter expressed as the ratio of phantom to free air value at various phantom-chamloer distances is shown in Figure 14. In the present study, an intercomparison check was m.ade at 20.5 and 40 cm, two distances that are representative of the chamber to incident patient surface distances for fluoro and radiographic exposures. A 32 x 28 x 12 cm. water phantom 2 2 was used. The beam size was 10 7 cm. and 20 4 cm at the surface of the phantom for the respective phantomchamber distances and the x-ray unit V7as operated at SO kVp . Measurem.ents v/ere made v/ith a Victoreen 555 and 555-0. iMA chamlDer positioned at the same irradiation distance as the targettophantom surface distance. This chamlDer location allowed determination of the incident x-ray exposure without backscatter. Four free air exposures and four exposures with the water phantom in the beam, v.'ere alternately m.ade at each distance. The multiple exoosures were carried out to help


60 average out any variations in the output of the x-ray unit or reading of the model 555 dosimeter. The R output for the phantom exposures v/ere assumed to be equal to the average exposure for the four free air measurements. The effect of backscatter at 20.5 cm was found to increase the Diamentor reading by 3.3%. At a 40 cm phantomchamber distance, no increase was noted. These values are also plotted in Figure 14, and are seen to be in agreement with the p\±)lished data of Ardran and Crooks. Energy dependence Triplicate calibration checks ware obtained at indicated tube potentials of 60, 80, 100 and 120 kVp. Using the measured HVL of 3.3 mm Al at 80 kVp for the Machlett Dynamax 69B tube housing asserribly v/ith collimator and PTW ionization chamber, representative HVL values for the other tube potentials were determined from the values of Reinsma (1960) . Using these HVL values, appropriate correction factors for the Victoreen 555-0. IMA chamber measurements v/ere applied to the measured PTW calibration factors. The results are shov/n in Table 8. These data indicate a m.aximum variation of 3% for the PTW system over a tube potential range of 60 to 120 kVp.


61 Td ^o


62 Q) a, N > •ri M Q) O rH e CO (c M > o o MIS +J -Pi fa


CHAPTER IV RADIATION EXPOSURE TO CLINICAL PERSONNEL A number of authors have reported on radiation exposure received by clinical personnel during cardiac catheterization procedures. These published data shov; a large variation in results. This night be expected since each study generally was carried out in a single institution and the variation between studies reflects differences in factors such as equipment configuration, room layout, patient classification and procedural techniques. Although differences in personnel exposure exist, the general levels reported demonstrate the potential for high operator exposure during this classification of diagnostic special procedure. The ICP.P (19 73) has noted the large increase in the number of coronary artery examinations that has taken place during the last few years. Wholey (1974) states that it has been estimated that 80% of the coronary artery cardiac examinations are currently being performed by cardiologists. In the nine hospitals visited in the field survey described in Chapter II, only two were under the control of a department of radiology. In the majority of cases a cardiologist had sole responsibility for the layout of the room, purchase of the equipment and day-to-day operation of the 63


64 catheterization laboratory. Often the cardiologist had received no specific training in radiology or radiation protection. The technical support staff is also typically composed of individuals with little or no x-ray background. Although an x-ray technologist may be associated with the cardiovascular examination team, the support staff is usually drav/n from other areas. Currently there are three associate degree programs in the U.S. to train cardiovascular technologists. The number of individuals v/ith this formal background are presently insufficient in number to meet the needs of the large nximber of cardiac special procedure laboratories in operation. Thus, individuals v/ith backgrounds in nursing, pulmonary function, bioengineering , etc., are often recruited to work as part of the catheterization team. Their training is primarily on-the-job and v/ould be expected to be m.inimal in areas relating to radiation protection. Cardiac catheterization is a manipulative surgical technique. The aseptic conditions that must be maintained restrict the use of scatter shields such as the lead rubber flaps that are normally attached to a fluoroscope since they cannot be conveniently sterilized. The physician cannot wear protective lead gloves since their use v7ould inhibit his ability to manipulate the catheter.


Because of the potential for high personnel exposures in cardiac catheterization, a detailed evaluation of typical exposure levels and their relationship to classification of personnel, equipment configuration and procedural methods was performed. Literature Review Hills and Stanford (19 50) reported on radiation exposures to surgeons, anesthesists and radiologists involved with catheterization and angiographic studies of the heart. The techniques and equipment used at the time of their v/ork differed significantly from those utilized today; therefore the results of their study are of historical interest only. Fluoro was perform.ed v/ith a conventional direct-viev; fluoro screen. A home-m.ade photof luorographic camera with a 5 x 5 inch Eastman Kodak aerial caraera v/as utilized for singleplane rapid-sequence filming (Hills, 1948). An operational limit of 20 minutes of fluoro was placed on any single examination. This time limit v/as esta.blished to limit the exposure to a typical patient examined on their equipment to onefourth an erythema dose. More recently, Wold and colleagues (19 71) placed TLD ' s at 13 body sites on physicians performing cardiac catheterization studies. The x-ray setup utilized an under table x-ray source and over table image intensifier. Although their report states that operational values for fluoro time,


66 fluoro and cine current and feet of cine film were recorded, this information is not presented in their published results. The average exposure to the dosimeter positioned on the forehead (eye indicator) v/as 26 mR per procedure. This site received the highest fraction of the appropriate maximum permissible dose equivalent values recommended by the NCRP (1971) . Malsky and colleagues (19 71) reported on exposures to physician and auxiliary personnel while performing coronary arteriography using the Judkins technique. The procedures were carried out on a single-phase x-ray unit equipped v/ith a 22 cm diameter (nominal nine inch) image intensifier. The reported fluoro times ranged from 4 to 20 min with 4 min of associated cine (no frame rate or footage of cine film was given) . The beam size at patient entrance surface v/as stated to be in the range of 180-330 cm^ . Ardran and Fursden (19 73) reviev;ed the film badge records of 17 individuals in one institution involved with the conduct of cardiac catheterization examinations. The badges were worn under the protective lead apron; and Ardran calculated the average exposure to the protected trunk of the body to be approximately 2 mR per procedure. In addition, he measured the exposure at four sites on the body of 20 cardiologists involved in 18 procedures. The catheterization examinations averaged 18.6 min of fluoro and 35 sec of cine. The threephase x-ray unit used in these procedures v/as equipped


67 with a 22.8 cm diameter (nominal nine inch) image intensifier, but no recording of actual beam size used in the procedure was given. A tabulation of the exposures reported by Wold, Malsky and Ardran are shown in Table 9. A comparison of the exposure values for these studies shows the Wold and Malsky levels to be significantly higher than those of Ardran. The only real difference between the Malsky and Ardran procedures seems to be the average cine time, 4 min reported by Malsky, versus 35 sec by Ardran. The V7old data cannot be evaluated since no operational factors are given. Ardran states that if the values for his exposure measurements were extrapolated to account for an average of 4 min of cine the personnel exposure would still be considerably less than those of Malsky and colleagues. These differences can only be accounted for by presently undefined conditions unique to each institution. It is improper to say that the lov/er values reported by Ardran must be achieved by every catheterization laboratory since factors such as classification of patient, equipment configuration, procedure format, etc., must also be considered. The value of these studies is the illustration they provide regarding the existing institution-to-institution variation in operator exposure.


68 TP3LE 9 Reported Physician Exposure Per Procedure at Indicated Site


69 shields and protective side panels for both tube and table are all essential features that must be included for this configuration of equipment. The "Year 2000" report of the special study group for the Federal Radiation Council on Estimates of Ionizing Radiation Doses in the United States, 1960-2000 (Element et al,, 19 72) gives a breakdo\\m of occupational radiation exposure. The reported values were based primarily on occupational exposure records for the period 19 69-19 70 obtained from the military services and other Federal agencies involved with radiation, as well as data from state and nongovernmental sources. The report lists an estimated mean annual dose of 210 mrem/worker for an occupationally exposed population of approximately 772,000 individuals. The subcategory of medical x-ray workers constitute 26.4% of these individuals. Table 10 gives a summarv of these exposure values for the various em.ployer classifications V7ith a breakdov/n in the medical related area. The report of the United Nations Scientific Committee on the Effects of Atom.ic Radiation (19 72) also reports values for occupational exposure to personnel in various countries. In the category of medical employment associated exposure, the values range from 70 to 380 mrad/year with the U.S. listed as 340 mrads/year.


70 (U S-l < 0) ^ -P -P fO CD C M O >H tn -P u O (C -H a o tj K *+-! S •H rH W !-l (C CO O OJ iH o > CXM-I g o H O >^ m QJ CO 0) (t


71 In reviev/ing these occupational exposure levels, one must keep in mind the fact that the primary sources of these data are personnel exposure records. Personnel monitoring programs are established to provide an index of exposure, as contrasted to exact dosimetry data. Factors such as the variation in the site of dosimeter placement on the body, lack of standards for accuracy of dosimeter reading, and the variation of units of reported exposures (i.e., R, rad, rem) by different personnel dosimetry services must be considered. An inability to accurately account for these factors as well as a limited data base for the non-governmental medical related exposures were identified in the "Year 20 00" report as resulting in the greatest uncertainty for the values reported in this category. Recorded Personnel Exposures in Ten Catheterization Laboratories The personnel m.onitoring records for individuals working in cardiac catheterization laboratories in ten hospitals in Florida were obtained. These data represent the results for 83 individuals, 38 physicians and 45 technicians. Tv/o of the hospitals were large teaching institutions and accounted for 58% of the physicians and 42% of the technicians in the survey population. It might be expected that the average yearly exposure per patient catheterized in these facilities would be less than in a small hospital since the large staff allov7s for personnel rotation.


72 The position of badge placement varied from facility to facility with a greater percentage of personnel selecting a site under the protective lead apron. Four physicians in one institution utilized monitors both outside and under the apron. Finger badges were utilized by six physicians at two facilities . Values for cumulative exposure were obtained as far back in time as consistent data could be found. In general, the information represents exposure histories up through at least August of 19 74. A summary of these data are shov/n in Table 11. In calculating the average yearly exposure, no data for individuals monitored for less than a quarter of a year are included. Of the 38 physicians for which exposure records were obtained, five had minimal non-detectable levels recorded. In at least tv/o of these cases the values are known to be inaccurate. One individual was the sole physician working in the catheterization laboratory. In the second case the individual had been performing catheterization examinations for over six years. During this entire six-year period the total cumulative exposure had been 20 mrem reported during one monitoring interval. In both cases it seems obvious that the monitoring badge was not worn. Since it vzas impossible to establish the frequency at v/hich badges may have not been worn, the data in Table 11 are reported as found in the records without adjustment. Errors of this type v/ould result in the tabular values being an underestimate of the actual exposure.




74 The values for the exposure to the hands varied drastically between the two hospitals at which hand badges v/ere worn. At one institution, v/here two cardiologists carried out all procedures, the average yearly dose to the hands v/as 12.4 rem. At the second facility at which four cardiologists wore hand badges, the average dose v?as 0.46 rem/year and the hand dose to no single individual was greater than 0.56 rem/year. The yearly patient load in each facility was equivalent; it was not determined if the difference was associated with physician technique, frequency at v/hich the badge was worn, or some other factor. Personnel Exposure Measurements i n University of Florida Cardiovascular Laboratory To determine more accurately the values for the expected radiation exposure received by the physician and technicians during cardiac special procedures, a series of body site measurements were m.ade during individual clinical procedures. Sensitivity paired TL dosimeters v/ere positioned at selected sites on the bodies of the personnel. The characteristics of the patient, examination techniques and the position of the personnel during the examination were recorded so that these factors could be related to the measured exposure levels. The dosimeter sites were selected so that an estim.ate of the dose to the eyes, thyroid, hands, gonads and whole body could be obtained. Figure 15 shov/s the selection of monitoring sites on the body. During the initial phase of


75 p;5 Site No 1 2 3 4 5 6 7 8 9 10 Identification Forehead Right shoulder Left shoulder Back of right hand Back of left hand Collar, under lead apron Collar, outside lead apron Gonad region, under lead apron Gonad region, outside lead apron Thyroid Figure 15. Identificati on o^ TL Dosimeter Sites for Exposure Measurements on Physicians and Technicians.


76 this study the exposures received during the examination of seven pediatric and six adult patients v/ere evaluated. The preliminary results of this v/ork were reported by Gignac (19 74) . Physician exposures during an additional seven adult patient study were subsequently carried out. For these measurements an additional dosimeter was positioned on the neck at the level of the thyroid (site number 10) to determine the difference between this position and the outside apron collar site (site nijmber 7) . During the first series of 13 procedures, the x-ray system was equipped v/ith a single-m.ode nominal six inch image intensifier. In the additional measurements for which the added thyroid site was monitored, the image intensifier had been changed to a dual-mode six inch to nine inch unit. During a catheterization procedure the clinical staff consists of at least one physician and normally three or four technicians. Since the University of Florida is a teaching facility, additional physicians, technicians or observers are often present. It is not uncommon to find eight to ten individuals present during a procedure. Figure 16 shov/s a floor plan of the procedure room. The floor was marked off with tape into eight numbered zones. These zones arc delineated in the figure V7ith dashed lines. The patient lies on the tarjle with his head tovzard zone three. The physician conducting the procedure occupies zone one and is positioned next to the extended arm or groin of the


77 E'luoro and physiological TV monitors Blood-gas analysis equipment Biplane changer control ographic view box -l-f-f-4SCALE Figure 16. Room Layout of the UF Cardiovascular Laboratory Showing Work Zones.


patient into which the catheter is inserted. One technician remains in zone two. This person will raise and lower the image intensifier, assist the physician from this crosstable position and give physiological aid to the patient. A second technician occupies the area in zone three at the head of the table. The controls for beam limitation and table movement are the primary responsibility of this individual. A third technician, v/ho night be thought of as a floater, will usually be present in the room. This individual will move through zones four, five and six assisting the physician and operating the blood-gas analysis equipment located on the counter top area in zone six. A technician is also positioned behind a glass panel and has the responsibility for operating the physiological recording equipment. At the start of the procedure the TLB's v/ere placed on the physician and three of the technicians; those intending to occupy zone two, three and four-five-six respectively. The dosimeter pairs positioned on the hands of the physician at sites four and five v/ere positioned on the back of the hands under the surgical gloves. The sealed dosimeter package attached to the hands v/as sterilized in a liquid solution for approximately 30 minutes prior to the start of the procedure. A log of patient and procedure information v/as maintained. The exposure and associated examination factors are given in Appendix D. Tables 12, 13 and 14 list m.ean and range values for the exoosui-e measurements at the various sites.



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80 Q w C CO (T3 C •H O O -H •H -P O -H O 3 U tn nj o Q) (C m ^^ O n3 U >i M c

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81 c

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82 The average fluoro time v/as 14.7 minutes for the adult catheterization procedures and 22 minutes for the pediatric. Cine was utilized in all adult studies and in 43% of the pediatric cases. The average number of cine frames exposed was 2,483 and 775 respectively. At 64 frames per second this is equivalent to 39 and 12 seconds of cine. No data V7ere recorded regarding the biplane procedures carried out on the pediatric patients since all personnel leave the room during these rapid sequence filmincs and the exposure to operating personnel is negligible. During the initial 13 procedures in vrhich a comparison betv/een adult and pediatric exaraination technique could be obtained, it v/as seen that adult catheterizations resulted in a greater exposure to personnel than pediatric examinations. In addition to the greater patient thicknesses, which require higher incident exposure., the predominant use of cineradiography during adult examinations is the cause for these higher exposures. It was found that considerable nonuseful exposure occurs during the examination; this was due mainly to the "cine test" procedure, v/hich accounts for 19% of the total exposure during the examination. This test procedure was required to be carried out prior to the actual cine run. The x-ray system utilized a current modulation automatic brightness system. The dynamic range of this systeia was limited and the cine test was carried out to set the current level at a nominal midrange operational point. The procedure

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83 consisted of making a test exposure during which the x-ray tube was activated, but the cine film was not advanced. During this exposure the tvhe potential was manually adjusted to a value that v/ould allov/ the required brightness level to be achieved at a mid-range ti±»e current setting. The test setup was required at the start of the first cine run and prior to subsequent runs where the patient's geometry was substantially changed, such as occurred when the patient was rotated into the oblique positions. From a diagnostic standpoint the exposures received during these test procedures were of no benefit. An additional source of nonuseful exposure occurred as a result of the procedure used for identification of the cine film. Lead identification letters were used to spell out the patients name, hospital number, date and institution name. Prior to the first cine run the paddle on which this identification information was arranged was placed in the beam betv/een the patient and the input surface of the intensifier. A short strip of film, was then exposed and when developed v/ould serve as an identification leader. This technique resulted in an average 2% increase in incident exposure to the patient. When the single-m.ode , nominal six inch, image intensifier and current-m.odulated automatic brightness control system were replaced by the dual-mode, six inch to nine inch unit and kV modulated automatic brightness system, the test exposure was no longer required and the unnecessary

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84 exposure associated with the test procedure v/as eliminated. It also became standard operating procedure to mark the cine film prior to arrival of the patient. From Table 12 it can be seen that the highest exposure to an unshielded body site received by the cardiologists involved v/ith adult patients v;as measured on the left shoulder (site number 3) . With the exception of the exposure to the hands, the values recorded during the adult patient studies were about double those received during the pediatric studies. This is logical since one vj-ould expect a higher scatter level to be associated v/ith the larger adult patients. Cine techniques were utilized in all of the adult patients studied, but in the pediatric catheterizations they v/ere employed less than 50% of the time. The number of cine frames per procedure for the adult studies was more than three times that used in the pediatric studies. As previously noted, during the biplane rapid film radiographic techniques employed for the evaluation of congenital heart defects in children, all personnel leave the procedure room and thus receive negligible exposure. The higher exposure to the hands of the physician performing catheterization procedures on children results from their closer proximity to the primary beam. The technician working in zone tv7o during an adult catheterization study receives exposures similar to those incident on the physician. Where the left shoulder had been

PAGE 105

85 observed to be the high unshielded site for physicians, the right shoulder of the technician is seen to be highest. This can be correlated with the normal position of these two individuals. The fluoro and physiological TV monitors are positioned near the foot end of the procedure table. As a result of this placement the left and right sides of the physician and technician are positioned closest to the patient or source of scatter radiation. The measured exposures received by the technicians in zones three and four-five-six are seen to drop off sequentially from those recorded for zone tv/o . The values are generally higher for the adult studie-. . As previously noted, during the first series of measurements the thyroid was assumed to receive the same exposure as recorded by the dosimeter positioned on the outside of the protective lead apron at the collar (site number 7) . A comparison of the values in Tsible 12 for the actual measurements made over the thyroid with those at the collar of the apron (sites 7 and 10) establishes the validity of this assumption. Although no correlation betx^7een surface exposure and absorbed organ dose is made, sites 1, 4 and 5, 8 and 10 are indicators of exposure to the lens of the eye, hands, gonad and thyroid respectively. For v/hole body exposure a single site estimate cannot be used since body surface exposure at different sites varies considerably. If blood-forming organs were considered the critical tissue (NCRP report 39, 19 71,

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86 page. 19 6) for whole body exposure, a weighting system based on its distribution in the body can be developed. Jones (1964) carried out a series of phantom dosimetry measurements to determine the dose absorbed in various organ systems as a function of the incident external exposure. The exposure at sites v/ithin and on the surface of the phantom were measured with TLD for beams incident on the AP surfaces, as well as for a rotational setup. In addition, exposures at the sam.e points in space were measured in the absence of the phantom. For an effective energy of 38 keV, which is similar to the energy of scattered x-rays received by personnel during diagnostic procedures, the bone marrov; dose to free air exposure for the three exposure geom.e tries v;as found to be approxim.ately 0.25 rads/R. The relationship between the exposure measured at a typical personnel monitoring site on the anterior chest surface, at the level of the seventh thoracic vertebra, was also found to be related to the bone marrow dose by a factor of 0.25 for the incident anterior and rotational geomietries . Figure 17 shows the outline of the human body with a lead apron typical of that v/orn by operating personnel in a cardiac catheterization laboratory. The body has been divided into four major zones which include: the head and neck down to the seventh cervical vertebra, the arm and exposed shoulder outside of the lead apron and the trunk of the body predominantly covered by the apron. The bone marrow

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Identification of TLD monitoring locations given in Figure 15. Figure 17. Svibdivision of Body of X-ray Operational Personnel Wearing Lead Apron with Identification of Active Bone Marrow Fractions .

PAGE 108

88 distribution for these respective areas, based on the data of Ellis (19 61) , is shovTTi in Table 15. Using these bone marrow distribution values and the relationship between incident exposure and bone marrow dose of Jones, a v/hole body "bone marrow dose index" can be derived as follows : Whole Body Bone Index = ( Sites 1+7+10) (0.165) (0.25 ) + 3 ( Sites 2 + 3) (0.02) (0.25 ) + ( Sites 6+8) (0.815) (0.25 ) 2 2 TABLE 15 Red Bone Marrow Distribution in Bodv Zones Identified in Figure 17 Mass of Percent of Body Anatomical Marrow^ Total Bone Zone Location (g) Marrow Cranium. Mandible Cervical vertebra 124,

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89 The measured exposure values received by operating personnel were interpreted in terms of the established radiation protection guides for various tissues. The follov^ing yearly workload assumptions v/ere used to develop estimated annual dose values : 1. A staff adult cardiologist performs 250 procedures per year. 2. A staff pediatric cardiologist performs 125 procedures per year. 3. A technician may assist in the procedure room during 300 examinations per year. The patient classification will be evenly split between adult and pediatric. An equal rotation of duties will result in one-third of the time being spent in zone two, three and four-five-six respectively. The results of this evaluation are presented in Table 16. Scatter Levels Around Examination Tables The requirement for a sterile field during cardiac catheterization has previously been noted. This requirement, which usually results in the absence of a scatter shield attached to the equipment, results in exposure levels higher than for other fluoro procedure rooms such as a typical gastrointestinal suite. Since scatter radiation cannot be adequately controlled through the use of a drape shield, the design of the table becomes a matter of primary concern.

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90 M O >i+J Xi (« u Td O (1) ^ > (C H 1-1 a) p CO u :3 > m o O -H Cund x; 5^ W (C o •rH C a, en O (C O -H o o -H S-l u (0 0) (U EH >H tn •rH en O -P O 3 •M 'C 'O < 5h C Q (UU U) 4-' O G C 0) >i m g rH > QJ 0! tr

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91 Exposure Measurements for Under Table X-ray Source A number of different source-patient-image receptor configurations are used. The most comjnon setup consists of an under table x-ray source and over table image intensifier assemi)ly. The geometry of the source-image receptor combination is fixed, except for allowing variation of source-toreceptor distance. The patient examined on this type of equipment is positioned on a floating-top table and positioned in the beam by controlling table motion. The table typically allows use of a flat or rotation cradle surface. If serial radiography is to be carried out, it is usually desirable to position the patient as close to the film changer as possible to reduce the magnification effect. To accomplish this, the flat table surface is employed. For studies such as coronary angiography, cine is the predominant recording mode and it is necessary to rotate the patient for various oblique projections. To accomplish this the patient is strapped in the rotation cradle. Tables of this type in current use have either interchangeable tops or have an add-on cradle that is positioned above a permanent flat table surface. The table currently in use at the UF cardiovascular laboratory is of the add-on cradle type. Using an adult Rando phantom, radiation scatter levels in various planes were measured with the phantom on the table and in the cradle. String v.'as used to establish a grid which identified measurement sites on 30 cm centers. The x-ray system was then operated in the fluoro mode and measurements

PAGE 112

92 were made with a Nuclear Chicago,^ Model 2588, cutie pie type survey meter. The x-ray technique factors were adjusted in accordance with standard operational procedures. Tube potentials of 80 and 9 2 kVp at a tube current of 2 mA were used for the flat table and cradle configurations respectively. These settings resulted in an optional fluoro brightness level reading of 100 units representative of normal operating conditions. The input surface of the im.age intensifier assembly was positioned 5 cm from the anterior mid-chest surface of the phantom. The intensifier v/as operated in the nominal six inch mode with the edges of the rectangular x-ray field tangent to the circular visible image (exact collimation) . Figures 18 through 2 shov; the isoexposure rate contours determined with the phantom on the flat table surface. Figure 18 represents a plane perpendicular to the longitudinal dimension of the table and intercepting the central axis of the x-ray beam. This position is approximately that occupied by the physician during a catheterization procedure. The vertical plane at the head of the table is shov/n in Figure 19. At this position, occupied by the technician in charge of table movement, the exposure rates are seen to be less than at the side of the table. At this head-of-tai)le position, the distance to the central axis of the x-ray beam is greater ^Searle Analytic Inc. (formerly Nuclear Chicago), Des Plaines Illinois .

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93 -P a, 0) o S-l (D -p c • H OJ o (D fO X3 >^ E-i W 4-1 CD O r-\ Q) fS •H CO +J

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PAGE 115

95 Exposure conditions : Under table x-ray source 80 kVp Nominal six inch mode Exact collimation Figure 20. Isoexposure Contour in Horizontal Plane at Table Top Surface Height. Adult Phantom on Flat Table Surface .

PAGE 116

96 than at the side of the table. The amount of patient tissue between the incident beam and the exit patient surface is also greater for this position thus providing a greater attenuation of scattered radiation. Figures 21 through 2 3 show the scatter levels in the vertical and horizontal planes with the patient in the cradle. As noted by the increased tube potential required for operation in this configuration, a higher x-ray tube output is required. This is due to the added attenuation of the cradle and the greater source-to-image receptor distance. The elevated position of the patient when positioned in the cradle results in a significant amiount of backscatter. These effects are seen to increase the exposure rate at the side edge of the table by a factor of approxim.ately five times over that measured for the flat table geometry. The exposure levels at the head end of the table are not seen to be significantly different for the flat table or cradle position. The head end cradle support houses the motor drive assembly for this apparatus and also provides additional shielding . The back and side scatter could be considerably reduced by addition of some type of scatter shield. To evaluate such a modification, a 0.5 mm strip of flexible lead vinyl v/as attached to the edge of the cradle. The length v/as such that when the cradle was in the extreme right anterior oblique

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PAGE 118


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99 2.5 mR/h /^<~\S ir.R/hr Exposure con Under table x-ray source 80 kVp Nominal six inch raod Exact collirnation Figure 23. isoe xsoexposure Contour" in Horizontal Plane at Flat C?adL w^t ^^ ^'":^-"''^^^'^ ^^^-t°i^ Rotation cradle wxtn ^.catter Shield Added.

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100 position the drape still extended over the edge of the table. The isoexposure rates for the horizontal and tv/o vertical planes are shown in Figures 24 through 26. Figure 26 represents a plane 30 cm above the flat table surface. The isoexposure contours, although differing in shape, somewhat correspond to those previously measured in the horizontal table top plane with the phantom on the flat table surface (Figure 20) . This is as expected and indicates that these values would be consistent with the expected exposure rates for a removable cradle that fits flush v/ith the edges of the table structure. Expected Exposures for Other Configurations In addition to the conventional under table x-ray source configuration, over table and C-arm units are in use. The potential for high personnel exposures from an over table fluoro x-ray source have been noted by Jacobson (19 71) . These result primarily from backscatter from the primary incident beam and the increased probability of getting the hand in the primary beam. Stacey and colleagues (19 74) reported on a comparison of personnel exposures from units with under table and over table x-ray tubes used for cardiac catheterization. From a design standpoint, the over table source has tv/o advantages. First it is not necessary to provide an additional x-ray tube for use with an under table serial film changer. The

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102 O tC . u
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10 3

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104 second advantage results from the fact that serial radiography can follov/ fluoro without moving the patient. These advantages are counter balanced by much higher scatter levels. Stacey measured the exposures to the same group of cardiologists working with the under table and over table systems. Although the exposure to the forehead was found to be slightly less for the over table configuration, the levels at the chest, waist and shins were increased by factors of three, 40 and 60 respectively. An estimated increase in physician bone marrov/ dose by a factor of 1.7 was given for the over table unit. Wholey (19 74) has also reported on the potential higher exposure levels that v/ould be expected v/ith an over table x-ray source. The C-arm configuration, v/hich is specifically designed for acquired heart disease studies, is currently available with various modifications from at least four manufacturers. In these units the patient is placed on a flat cantilevered table. The source and image receptors are mounted on opposite ends of a C-or U-arm. This assembly is rotated instead of the patient to achieve the oblique projections. Although no measurements v/ere made on a unit of this type, one might anticipate the operator exposure to be equal or greater than that expected v/ith an over table source. Shielding to reduce backscatter is not used and the rotational freedom would be expected to increase the possibility of the physicians or technicians getting their hands in the beam.

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105 One of the manufacturers' advertised features of the C-arm configuration is the increased patient load that can be handled. In at least one of the available models, the removable table top fits on a patient transport stretcher. The increased efficiency is achieved by use of a preand postcatheterization preparation area. The initial patient preparation, including cutdov/n and vessel isolation or percutaneous puncture is carried out in the preoperative area. The patient is then moved to the x-ray suite. Following completion of the examination, the patient is again m.oved to a postoperative area. By proper scheduling an increased patient load can be accomjnodated since the x-ray equipment is tied up during the examination phase only. This increased efficiency only compounds the potential radiological hazards . These units should be viev/ed with extreme caution and may be acceptable only vrhen sufficient staff is available to allow liberal rotation. Protective Lead Aprons The use of protective lead aprons by personnel involved with diagnostic x-ray procedures is a well-accepted principle. However, the selection of the correct design and weight for the apron to be used in a particular room is often overlooked. A knowledge of the duties and work habits of the v/earer must be considered in relation to radiation scatter levels. In terms of the accepted health physics goal of reducing

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106 unnecessary exposure to a iriir.imxim, an apron providing the maximum x-ray attenuation should be worn. In practice this must be balanced against the physical strength of the individual and period of time over vrhich the apron must be worn. At the UF cardiovascular laboratory both 0.25 and 0.50 mm lead-equivalent aprons are available. With the exception of a fev/ male physicians who use the 0.50 mjTi. variety, all other personnel routinely select the lighter one. The v/eight of the 0.50 mm aprons currently used is too great for the average female to v;ear for the two to three hours that m.ay be required to complete a procedure. In a cardiac catheterization special procedure room., it is a common practice to see one or m.ore of the technicians v/ith their backs to the patient. These individuals, who may be running physiological monitors, blood analysis equipment, etc., have often been observed to wear their apron on their back or use an additional lap apron strapped across the lower back. Although these solutions are adequate if correctly employed, it is difficult to assume that the person who finds it necessary to position the apron on his back will not turn and face the patient and source of x-ray scatter from time to time. If a second device, such as the lap apron, is required for adequate protection, it would be expected that it would be forgotten from time to time. Over a period of one month the external exposure on the surface of tv/o protective lead aprons v/as mieasured.

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107 Thermoluminescent dosimeters were attached at 14 sites on each apron, as shown in Figure 27. The aprons were randomly worn by physicians and technicians. No was made to record this frequency. The chips were removed and read after the first, second and fourth weeks. The results of these m^easurements are shown in Table 17. The maximum exposure is seen to be at the m>id-chest position (site number 5) . This is consistent with the maximum scatter levels measured at this position. The exposure at the two sites on the back of the apron (sites numbered 13 and 14) are seen to be less than 10% of the mid-chest values. Using these exposure m.easurements in conjunction with an understanding of the flow patterns in a typical special procedure room as a guide, a set of criteria was developed for the optimum protective lead apron for use in a cardiac catheterization special procedure room. The criteria are as follows : 1. The maximum thickness of attenuation material must be in the and gonad regions. 2. Some shielding should be provided for the neck and thyroid region. 3. The apron should provide wrap-around 360° protection for the lower pelvic area. Figure 2 8 shov/s a sketch of the proposed design. The length is intended to extend to the mid-thigh level of the wearer. This apron length is shorter than that provided by

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108 Level of: Figure 27. Position of TLD Monitors on External Surface of Protective Lead Apron.

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110 0. 25 mm Pb equivalent Meek-thyroid shield (removable) 0.5 nuTi Pb equivalent Figure 28. Wrap-around Lead Protective Apron with Removable Thyroid Shield.

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Ill the aprons in current use v/hich. extend to the mid-calf of a six foot adult male. This shorter length will allovr redistribution of attenuation material to areas of higher anticipated scatter and/or biological radiosensitivity . A detachable thyroid shield has also been added. This attachment is removable since it is only felt to be a mandatory prerequisite for individuals working directly next to the patient. Although the detachable shield could be inadvertently forgotten or put aside, this compromise is considered necessary so that one apron design can be used for all individuals in a special procedure room. The apron incorporates a wrap-around design with 0.50 mm lead equivalence over the gonadal area. To achieve a weight that is acceptable to the small female wearer and still provide adequate protection for the large male, aprons in proportioned sizes should be provided.

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CHAPTER V PATIENT EXPOSURE STUDY GENERAL CONSIDERATIONS An evaluation of the radiological health significance of cardiac catheterization procedures, as they relate to the patient, involves a number of considerations. In addition to quantification of the anticipated radiation dose, factors such as patient age and life expectancy are of key importance. If the examdnation involves a small population group v/here alternate diagnostic techniques do not exist and the absence of medical intervention will result in deterioration or life-threatening consequences, the concern regarding radiation exposure of the patient may be insignificant. Although the radiation hazards may assume a role of reduced importance in a benefit/risk analysis in some situations, every step should be taken to carry out those procedures that are felt to be necessary v/ith the minimum exposure. Advances in cardiac surgical techniques create a changing environment in v;hich the radiation hazards must be considered. These advances in operative techniques are continuously increasing the life expectancy of the patient. This, in turn, alters the anticipated somatic and genetic effects that may potentially be m.anifest in the individual. 112

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113 The majority of cardiac catheterization examinations are performed on patients suspected of having acquired heart problems with coronary arterial disease being the major contributor. The large e:Kpansion in the number of cardiac catheterization laboratories that has recently occurred in the U.S. are primarily involved with these adult patient studies. In many situations the patient is beyond the reproductive age and the somatic consequences need only be considered. As the availability of facilities equipped to perform these procedures expands , their use on an ever increasing population group can be expected, V7hen a medical facility invests one-half million dollars or more in a special procedure room, the patient load m.ust be m.aintained to cover the investment. The utilization of cardiac catheterization as a screening technique on healthy subjects in certain occupational groups , such as airline pilots , is already being used. In these situations the efficacy of the examination must be considered. Prospective Cardiac Catheterization Patients Accurate statistical data on the number of cardiac catheterizations currently performed, or age distribution of patients, do not exist. In the congenital area, a review of the incidence of cardiac defects will help identify the maximum patient population. Children evaluated for rheumatic heart disease must also be considered in this patient age category. The majority of adult acquired heart disease

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114 studies involve coronary angiography. In this case, statistical data regarding the individual v/ith angina pectoris who is a prime candidate for this examination, can be evaluated, A number of studies of the incidence of congenital cardiac defects has been reported. MacMahon and colleagues (1953) studied all children born in Birmingham., England betv/een 1940 and 1949. The total number of births during this period was 19 9,418. The incidence of cardiac defects diagnosed in this population v/as n.32%. The incidence of discovered defects increased in direct proportion to the length of time over v/hich the siobjects were follo^./ed. MacMahon states that the reported incidence frequency v/as suspected to be an underestimate due to this factor. Using methods similar to those employed by MacMahon, Richards and colleagues (1955) found an 0.8% incidence of cardiac malformations for infants born in New York City betv/een 19 46 and 1953. The study v;as based on a group of 6,053 children. Two studies originating from the Massachusetts General Hospital illustrate the influence of the tim.e period during V7hich a study is performed. McGinn and VJhite (19 36) reported that 0.9% of the patients seen by autopsy betv/een 189 5 and 19 35 were diagnosed to have had congenital heart defects. A later study for the period 1936 to 1951 by White (1955) shov/ed the identification of congenital cardiac defects had increased in number by greater than a factor of two. This change was

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115 not thought to be related to an increased frequency of this problem, but to a better understanding and siobsequent recognition of the specified defects. In reviewing the various published studies regarding the incidence of congenital cardiac defects, Fontana and Edwards (19 62) also point out this problem. They state that pathologic studies carried out by them through 19 6 2 indicate the incidence may be as high as one percent. The impact of surgical techniques, such as the insertion of prosthetic heart valves and coronary vein bypass grafts, have been one of the major factors associated with the increase in the number of adult patient studies. The ICRP (19 73) noted the increased number of coronary angiographic procedures that are being carried out and their direct relation to patient exposure. In the last few years the U.S. has experienced a drastic increase in the number of cardiac catheterization laboratories. The large majority of these facilities are concerned with the study of adult patients with acquired heart disease. The exact number of these facilities is not presently known, but based upon unpublished manufacturers sales projections, it miay be as high as 600. Since a majority of adult catheterization studies are for the evaluation of coronary arterial disease, the life expectancy of the patient with angina pectoris is of interest.

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116 White, Bland and Miskall (1943) reported that 90% of 500 patients seen in their practice and diagnosed as having angina died within eight years. In a follov/up report in which 456 of these patients were traced over a 25-year period, Richards, Bland and White (1956) found only 12 individuals alive at the end of the period. The initial 5-year survival in this study group of 456 was 64% for men and 74% for women and after ten years the survivals were 41% and 44% respectively. Block et al. (1952) reported on a much larger group of nearly 7,00 angina patients. They found an average annual mortality, after the first year, of about 9%. The 5-year survival rate V7as 58.4%. Kannel and Feinleik (1972) reported on the fate of angina patients in the Framingham study. In this study an initial group of 5,127 patients v;ere selected based on their absence of any clinical manifestation of coronary heart disease. In a 14-year followup, 492 individuals in the original group developed angina pectoris. The annual death rate for men in the angina group was about 4%. By the end of an 8-year period following the initial diagnosis of angina, 40% of those over the age of 50 v/ere dead. The death rate for patients in the Richards and Block studies is seen to be greater than that for the Framingham. group. This might be expected since the population study groups in the Richards and Block evaluation were composed of

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117 patients who had sought medical help for their angina symptoms. In the Framingham study, the angina subgroxip had evolved from an original asymptomatic population. It might, therefore, be expected that the Framingham group would include individuals \>;ith less advanced coronary complications. From the above studies it can be seen that the individual with angina pectoris, v;ho is a prime candidate for a coronary arterial examination, has a limited prospect of longevity. When considering the typical latent period of 10 to 20 years that may exist between the time of radiation exposure and the development of a carcinoma, leukemia, etc., concern for these somatic effects for this group of individuals is minimal. Genetic effects are also of little concern for a large segment of these adults due to the age of the typical patient studied for coronary artery disease. Reviev/ of Published Dosimetry Studies Recognition of the potential high radiation exposure that can be received by patients during cardiac examinations v/as reported on as early as 19 50 by Hills and Stanford. They state the risk to the patient undergoing this type of examination is that he m.ay receive a skin dose sufficient to produce some degree of "x-ray burning." During angiocardiography they used an over table x-ray tube and under table photof luorographic system.. This specially designed unit, described by Hills (1948) , vrould

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118 result in an incident exposure to the chest of an adult patient of approximately 1.3 R/frame of information. Fluoro was carried out with an under table x-ray tube and a conventional direct-viev; fluoroscopic screen. They state that a typical table top exposure rate for their system might be 5,5 R/inin. Based on this exposure rate, they limited fluoro time during catheterization to no greater than 20 minutes. These investigators reported typical patient entrance exposure levels of 136 R for a complete examination which included a chest film, a barium swallow with 3-1/2 min of screening, 20 min of fluoro during the catheterization portion of the examination and a 10 film angiographic series, Approximately 80% of the exposure was delivered during the catheterization phase of the cardiac examination. Larsson (1956) measured incident skin exposure during 32 cardiac catheterization examinations performed in seven hospitals. Sixty-three percent of the procedures involved exposures of less than 50 R, but one value of 20 6 R v/as reported. The advent of modern image intensifiers and fast film screen image receptor systems have resulted in a large increase in the amount of diagnostic information obtained per unit of incident exposure. Concurrent increases in the amount of diagnostic information desired during heart catheterizations have also occurred. As recently as 19 68, Gaugh, David and Stacey (19 68) reported incident skin exposures similar to those of Hills and Stanford.

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1.19 Gaugh and colleagues reported the estimated skin, gonad and bone marrow doses received by 91 patients having cardiac catheterization examinations in Brampton Hospital in London. The values for incident skin exposure were estim.ated from output calibration data for the x-ray unit used in conjunction with the recorded technique factors employed during a particular procedure . The gonad and bone marrow doses were in turn calculated using the incident exposure estimate v/ith beam size and patient geometry assumptions. Probably the greatest error in the Gaugh study was the fact that he had no way of measuring fluoro beam size and assumed a maximum of 20 x 20 cm (400 cm^) for the entire examination. This value may be as much as four times larger than is required or usually employed, according to measurements made by Ardran and colleagues (19 70) . Beam size is a key factor in Gaugh' s determination of bone marrow dose since the calculation is based on a known fraction of the ribs, sternum and number of thoracic vertebrae in the primary beam. For 85 patients, which included both pediatric and adult subjects, a mean marrow dose of 1.4 rads was reported. The maximum individual marrow dose was 3.81 rads. Estimates of bone marrov; dose received during cardiac catheterization have also been reported by Seidlitz and Margalis (1974). Phantom, measurements were made to relate body surface exposure to absorbed dose in the vertebral column. Surface exposures were then measured during ten

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120 clinical procedures. The mean integral vertebral marrow dose was 1,700 g-rads with individual values ranging from 760 to 2,900 g-rads. As part of a study of exposure to patients during angiographic procedures, Kaude and Svahn (19 74) reported on the male gonad and integral dose received during cardiac procedures. The examination facility in which the measurements were carried out was equipped with biplane im.age intensif iers , each with 35 miri cine and 70 mm fluorographic cameras. Biplane serial film changers were also used as an alternate mode of exam.ination. During five adult procedures, the mean male gonad dose v/as found to be 10 mrad and was reduced to 4 mrad by use of gonad shielding. For 12 examinations of children 15 years old or less, the mean gonad dose v/as reported as 13 and 2 80 mrads determined with and without testicular shielding. During 10 adult procedures, the mean integral dose was 5 8 kg-rad and for 12 pediatric studies it was 16 kg-rad. The range for the individual values in the respective groups were 17 to 101 and 1 to 42 kg-rads respectively. Although some measurements v/ere made during discrete phases of the procedures to estimate the contribution of different modes of viewing, the values for an entire examination as referenced above gave no breakdown as to the extent each mode of examination was utilized.

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121 The exposures resulting from cardiac special procedure work can be expected to vary from facility to facility. These variations will reflect the differences in technique, patient classification and equipment configuration. Rov/ley C19 74) compared the use of a 16 mm. cine camera operated at 200 frames per second to serial angiography. In pediatric cardiac studies, the patient doses were sim.ilar. For adult coronary studies , the exposure resulting from use of this high cine frame rate v/as felt to be prohibitive. When operated in the range of 50 to 100 frames per second, the combined fluoro and cine exposure in 37 patient studies had a mean incident exposure value of 41 R with individual values ranging from 11.5 to 100 R. New technical advances in x-ray equipment design may lead to reduced exposures in the future. Dorph and colleagues (19 70) and Grollman and colleagues (19 72,1974) have described the use of pulsed fluoro carried out with a video disk recorder. Grollman states that adult coronary studies carried out using this technique have resulted in patient dose reduction of up to a factor of three. The employment of pulsed fluoro and the v/ider use of 70, 100 or 105 mm fluorography have been noted by the ICRP (19 73) as areas where equipment developments m.ay aid in lox\7ering dose.

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122 Need for Patient Dosimetry Study Although a limited number of reports of patient exposure during cardiac catheterization procedures have been made, it is difficult to drav/ conclusions with regard to the radiologic significance of these exposures. The data were often obtained from mixed patient groups including both pediatric and adult siobjects. An adequate description of the equipment performance and examination technique v/as usually lacking. The exposure or dose index reported by the various authors also varied v/idely. Due to these shortcomings of the existing data, a study of patient exposure v/as carried out. This study included both phantom, and live patient investigations. The patient simulations and clinical patient studies v'ill be discussed separately in Chapters VI and VII.

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CHAPTER VI PATIENT EXPOSURE STUDY PHANTOM MEASUREMENTS Data necessary to estimate dose to selected internal patient body sites during cardiac catheterization v/ere developed by monitoring hinnan-equivalent dosimetry phantom.s withTL dosim.eters under typical e:xam.ination conditions. A commercial adult phantom was used to simxilate conditions of an acquired heart disease study, while two specially fabricated pediatric phantoms were employed to simulate congenital heart studies. The phantom mLsasurements were reported by Katta (19 75) . A description of the procedures and summary of the results will be reviewed. The internal organ dose values have been converted to units of absorbed dose instead of the R exposure units given by Katta. The values for the bone marrow dose have been recalculated to more accurately account for the amount of red bone marrow in the primary beam for the PA fluoro/cine projections. Adjustments have also been made in the bone marrow values for the AP and LAT radiographic exposure conditions to correct for geometric restrictions associated with the infant and child phantom.s . 123

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124 Descrintion of Phantoms Human-equivalsnt phantoms are commonly used to investigate the doses resulting from, the medical uses of ionizing radiation. Dosimetry at internal body sites, which is often impossible to carry out in live patients, is facilitated by the use of these devices. The ICRP and ICRU (19 61) have outlined a number of factors that must be considered in the makeup of a human representative phantom.. The effects introduced by the differences in composition of soft tissue, bone and air cavities must be considered. The photoelectric effect predominates in the energy range used in diagnostic radiology, therefore the differences in density and attenuation coefficient for these components that make up the body are important. To Simula phantom was used. The Rando phantom consists of a human skeleton surrounded by a thermosetting synthetic plastic. Alderson Research Laboratories (19 69) states this m.aterial has an effective atomic number of 7.30 and a mass density of 0.985 (both held to a tolerance of 1-1/4%) and represents a composite of muscle, normal body fat and fluids. The lungs a Alderson Research Laboratories, Stamford, Connecticut.

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125 are constructed of a microcellular plastic foam of density 0.32 + 0.01 having the same effective atomic number as that of the soft tissue material. Air spaces are provided to simulate the oronasal pharynges , the larynx, the trachea and the stem bronchi. Alderson and colleagues (19 62) state that the anthropomorphic specifications for the Rando are based on a U.S. Air Force survey of male personnel slightly modified to conform with results of a second civilian survey. The adult male model is proportioned to a representative individual 1.73 m high who weighs 73.5 kg (Lanzl, 1973). The phantom is divided into 2.5 cm thick transverse sections. Each section is subsequently drilled on 3 cm centers to facilitate internal dosimeter placement. The holes are plugged with removable Mix-D inserts (Jones and Raine , 19 49) . No commercial phantom is available to simulate the pediatric patient. From the review of the catheterization patient records (Chapter II) , the age at the tim.e of the catheterization was seen to have a bimodal distribution with peaks in the to 6-month and 5 to 6-year ranges. Representative phantoms in these two age groups were subsequently custom fabricated.^ The height and v/eight records Construction by private fabricator under sponsorsliip of the Bureau of Radiological Health, Food and Drug Administration, Department of Health, Education and Welfare.

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126 of t±Le UF cardiovascular laboratory were analyzed to determine representative values for patients in the tv/o age groups. Radiographs were subsequently obtained from patients matching the representative values to aid in the anatomical modeling of the phantoms. To simulate soft tis and beeswax was used. This m.ixture has a density of 0.9 4; it is solid and durable at room temperature but can be easily molded at elevated temperatures. The lungs were constructed of polystyrene foam having a density of 0.3. Inserted into the plastic foam, were the heart and pulmonary vessels made of the soft tissue wax m.ixture. The bones were fabricated from equal weights of calcium phosphate and calcium carbonate mixed with melted paraffin. The ratio of calcium to wax was varied until a simulated bone producing the same radiographic density as an equivalent-sized sample of bone was obtained. The mineral content of this simulated bone material typically accounted for 65 to 75%, by volume, of the bone phantom material. The skeletal structure was first molded from the bonesimulation material. The lungs were inserted and soft tissue was then added to build up to the normal external dimensions of the representative subject. The head was removable and a Microcrystaline wax manufactured by the Exxon Corporation.

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127 the chest was sectioned so that mid-plane dosimeter sites could be used. The dimensions of all three phantoms are given in Table 18. Figure 29 shows a photograph of the sectioned adult Rando phantom. Photographs and whole-body x-rays of the representative 6-month and 6-year old phantoms, which will siibsequently be referred to as the "infant" and "child" phantoms are shown in Figures 30 through 33. Phantom Dosimetry Sites Radiation measurements were made at multiple external and internal sites on the phantoms with TL dosimeters. The sites were chosen so that the doses delivered to the bone marrow, thyroid, gonads, skin (entrance exposure) and lens of the eye could be determined. Liver and spleen were also monitored for the pediatric exposures. Physiologically the liver and spleen play a role in erythropoiesis and lymphopoiesis during the early stages of life, while the bone marrow is the chief hematopoietic organ. Although the exact radiobiological consequence of exposure to the spleen and liver during this early stage of life is not known, some indication of the dose delivered v/as felt to be important. Ten external body sites were monitored with TL dosimeters. Table 19 and Figure 34 identify these sites. For the measurements made with the adult Rando phantom, 2 8 internal body sites were chosen. Tv;enty-four v;ere

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129 / Figure 29. Alderson Rando Phantom,

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131 Figure 31. Whole Body X-ray of Infant Phantom,

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133 Figure 33. Whole Body X-ray of Child Phantom.

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134 TABLE 19 Location of External Dosimetry Sites on Phantoms and Patients Site Number Location' a See Figure 3' 1 Forehead at glabella 2 Right lobe of thyroid 3 Left lobe of thyroid 4 Anterior mid-chest (mid-sternum) 5 Left lateral mid-chest 6 Posterior mid-chest 7 Right lateral mid-chest 8 Anterior lov/er abdomen 9 Posterior lower abdomen 10 Left inner thigh adjacent to scrotum

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135 Figure 34. Location of External Dosinetry Sites on Phantoms and Patients.

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136 associated v/ith determination of the bone marrov/ dose and two each with thyroid and ovarian estimates. In the two pediatric phantoms, 18 internal sites v/ere used, 13 at selected bone marrov/ sites, two at the thyroid and one each at the assumed location of the ovaries, spleen and liver. Adult Bone Marrow Sites Any method of estimating exposure to the total bone marrow must take into account the distribution of active marrow in the skeleton. Relatively little research has been conducted to determine the bone marrow distribution in adults and children. Ellis (19 61) described an estim.ation of the active bone marro;-/ distribution in the 40-year old adult. Qualitative distributions of marrow in humans had been studied by Piney (1922) , Higgins and Blockson (1963) and Custer (1949); and a study of the quantitative distribution of the marrow space was conducted by Mechanik (19 26) . Ellis applied a correction factor, based on Custer's work on cellularity, to Mechanik 's data to generate the percentage of active red bone marrow in each bone of the 40-year old adult. These results, tabulated in Appendix E, were utilized in the adult bone marrow dose calculation. To estimate the bone marrow dose, a method similar to that employed by Liuzzi et al. (1964) was utilized. The adult human skeleton was subdivided into a total of 15 subfields, as shown in Figure 35. In the establishment of the subfields, the fractionation of individual bones was avoided

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138 as much as possible to facilitate the determination of the marrow fraction in each s\.ib field. The mass of red marrow in each subfield was determined by identifying each bone, or part of bone, in each subfield and assigning that bone with a mass of the red marrow from Ellis' distribution. Appendix E gives a detailed breakdown of the bone structure and red marrow mass within each of the 15 subfields. Dosimetry sites were then selected so that exposure values representative of the entire subfield could be obtained. The adult phantom subfield sites are listed in Table 20. Pediatric Bone Marrow Sites Since anatomical differences in bone marrow distribution of children and adults are present, it was necessary to develop a different model for pediatric total average bone marrow exposure determination. VThile the bone marrow distribution in adults is fairly constant after age 25, there is a continual change of the distribution in children. No determination of pediatric bone marrow distribution was made until Hashimoto and Yamaka's study in 19 64. They determined the bone marrow distribution for 3 to 7-year old Japanese children. Although not expressly stated, the marrow distribution can be considered the red marrov/ distribution as nearly all marrow in the young child is active red marrow. The Hashimoto values were also used for the infant phantom since no better infant bone marrov/ distribution data exist.

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139 TABLE 20 Identification of Bone Marrow Dosimetry Sites and Red Bone Marrow Fraction in 15 S\±)fields of Adult Phantom Internal Fraction of Total Dosimetry Red Marrow in Sx±)field Site Subfield 1 Frontal bone 0.1236 Occipital bone 2 Mandible 0.0258 Vertebra (C4) 3 Vertebra (C6) 0.0252 4 Right scapula 0.0594 Right rib 3 5a Sternum 0.0224 5b Vertebra (T6) 0.1001 6 Left scapula 0.0594 Left rib 3 . 7 Right rib 7 0.0206 Right rib 10 8 Vertebra (T12) 0.1427 Vertebra (L 3) 9 Left rib 7 0.0205 Left rib 10 10 ' Right ilium ^ ' 0.1114 Right ischium 11 Left ilium 0.1114 Left ischium 12 Sacrum 0.139 2 13 Right femoral head 0.0191 14 Left femoral head 0.0191 Total 1.0000

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140 The same subfield model was used for the infant and child phantoms. The layout consisting of 12 subfields is shown in Figure 36. A detailed identification of the principal bone structures in each subfield is given in Appendix E. Table 21 lists the dosimetry sites and red marrow fraction for each subfield. Method of Interpreting Dosimetry Data The phantom TL dosimetry values reported by Katta were expressed in R exposure units normalized to an incident EAP of 10-^^. These data have beer, re-analyzed with regard to the method of calculation. The exposure values have also been converted to units of absorbed dose. For soft tissue such as the skin, thyroid and reproductive organs, an f-factor^ of 0.88 (Johns and Cunningham, 19 74) v;as utilized. Further consideration regarding the lens of the eye, reproductive organs and bone marrov/ doses are described in the following. Dose to the Lens of the Eye The production of a lenticular opacification is the biological effect of concern for radiation exposure to the eye. In an evaluation of patient exposure during carotid angiography, Bergstrom and colleagues (1972) measured the ^f-factor is the value used to convert values of exposure to dose (R to rad) .

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141 Pi \ Mi Figure 36. Location of Subfields for the Pediatric Phantom Model .

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142 TABLE 21 Identification of Bone Marrow Dosimetry Sites and Red Bone Marrow Fraction in 12 Subfields of Pediatric Phantom Fraction of Total Red Marrow in Subfield 0.0694 0.0516 0.0772 0.0250 0.0271 0.0922 0.0772 0.0516 0.1352 0.2875 0.0530 0.0530 Total 1.0000 Subfield

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143 lens tissue dose. Measurements in a 1 cm thick stack of TL dosimeters placed at the eye position on a representative human phantom were related to knov/n lid and lens distances for a standard model of the eye. Negligible difference between the dose measured over the eye lid and that to the center of the lens was found. The forehead site chosen for patient measurements during cardiac catheterization is only a few centimeters from either eye and would be expected to receive approximately the same exposure as a site on the eye lid. As shown by Bergstrom, the exposure measured at eye lid v/ould be expected to be representative of that at the lens. The forehead measurements v/ere thus directly converted to the lens of the eye dose by using the usual factors for exposure to dose conversion in soft tissue. Dose to Reproductive Organs To estimate the dose to the male gonads, a measurement site on the left inner thigh next to the testes was used. A more difficult problem is posed in selecting a dosimetry site for the female ovaries. The actual location of the ovaries is known to vary from individual to individual and will shift depending upon whether the woman is standing or in a prone position. In measurements of ovarian dose made by Morgan and Gehret (1971), the ovaries were assumed to be . in the center of the abdomen at a distance midway between

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144 a transverse plane passing through the superior iliac crest and the symphysis pubis. The selection of internal ovary sites was based upon this assumption. Bone Marrow Dose The dose to irradiated bone marrow is increased over that expected in a large soft tissue mass due to photoelectron emissions from, the surrounding mineral bone. This variation in absorbed dose is a function of the dimensions of the trabecular bone marrow space and the energy of the x-ray photons. The ICRU (19 59) points out that this change can be thought of in two v/ays : (1) the macroscopic distribution is altered by a reduction in intensity for soft tissue beyond the bone; (2) on a microscopic scale, the tissue adjacent to bone will receive a higher dose due to the increased number of photoelectrons from the mineral bone. Spiers (19 69) states that for photoelectrons produced from an incident energy x-ray beam of 200 keV or less, the particulate range in bone is of the same order as the thickness of trabeculae. Under these conditions, each cavity can be considered as surrounded by an equilibrium thickness of bone. For this case the calculation of bone marrow dose can be based on an assumed geomietry configuration of a single cavity. The size and geometry of trabecular bone spaces are of key importance in any analysis of the relationship between

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145 exposure and absorbed dose in bone marrow. Shleien (19 73) has reviewed the work of various authors regarding the dimensions of bone marrow cavities. With few exceptions, these studies have been isolated to adult subjects. The values are shown to vary over a range of 50 to 2,000 microns. The ICRU (19 59) states that representative mean dimensions might be 100 microns for bone lamellae and 400 microns for the marrow interspaces. Using this representative geometry, the ICRU gives calculated values for iriean dose (D) per unit exposure (X) for a cubical (plane slab) marrov; space geometry. Spiers has exam.ined both spherical and cylindrical cavities. He states that the values for the spherical model lie a little above those for the cylindrical. The spherical geom.etry is probably the best approximation of the actual trabecular structure . Figure 37 shows the values for D/X at various photon energies for the spherical, cylindrical and plane slab geometry. The dimensions of the TL dosimeters used in this study are large compared to the range of the photoelectrons in bone resulting from exposure to x-rays in the diagnostic region. Consequently the effect of the increased photoelectron emission from the mineral bone will be m.inimal and the chip readings can be interpreted directly in term.s of the R through its calibration value. The exposure to dose

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146 conversion values can then be based upon calculated values as shown in Figure 37. For a typical effective photon energy of 30 keV, the D/X conversion factor is observed to vary from 0.9 85 to 1.0 45. Since the exact shapes of the trabecular spaces are not known, the exposure and dose values were assumed to be equal. Katta determined the bone marrov; dose for each phantom and x-ray projection by multiplying the average measured exposure in each subfield by its representative bone marrow fraction and then summing these values over all subfields. Where this method seems valid for regions out of the incident primary beam, which receive only scatter or attenuated primary beam radiation, some error v/ill result for those subfields partially in the incident primary beam. An over or under estimate of the subfield contribution would be obtained depending on whether the measurement site is in or out of the primary beam. This error would be expected to be greatest for the PA fluoro/cine setups due to the large contribution of bone marrow in the vertebral column which is in the primary beam. Figure 38 shows a plot of the normalized exposure measurements at the vertebral marrow sites for the child phantom. Due to the lack of measurement sites, it was assumed that the intensity did not vary over the dimensions of the primary beam. Similar curves v/ere obtained for the adult and infant phantoms. By physical inspection of the phantoms and x-rays

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147 1.2 1.1 1.0 _. 0.9 -^ 2^ Spherical bone marrow interspace, Spiers (1969) . Cylindrical bone marrow interspace, Spiers (1969) . Plane slab geometry, ICRU (19 59) 25 50 75 100 PHOTON ENERGY (keV) Figure 37. Average Bone Marrow Dose per Unit Exposure at Marrow Site.

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148 asoa woHHvw awoa TVHaai.HaA aaziT^fwaoN 0) -P

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149 of their vertebral structure, the vertebrae in and out of the primary beam were identified. The individual vertebra were separated into three subclasses; those in the primary beam, a transitional segment at the edge of the primary beam and those receiving only scatter radiation. Table 22 lists the breakdown of the vertebrae for the various exposure conditions • The bone marrow dose contribution for these vertebral sites was then calculated. For each case a dosimeter site vzas located in the primary beam and its reading was used as representative of all vertebrae in the primary beam. A factor of 0.5 and 0.05, of this primary beam value, v/as used to estimate the dose received by vertebrae in the transitional and scatter zones. A second correction to the Katta results was made for the AP and LAT radiographic projections of the child and infant phantoms. During live patient serial biplane radiography, the arms are lifted over the head or positioned out to the side so that they will not be observed in the lateral chest image. The position of the phantom arms could not be changed from their normal position at the side of the body. The dosimeter site for subfields 2 and 6 containing the humerus, radius and ulna was located in the primary beam of the LAT beam and at the edge of the beam for the AP beam. Use of these nonrepresentative values v;ould result in an overestimate of the bone marrow dose. The measurement site in

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150 C en U U m O U X (C H E H e M O d CD M fd O U 4-1 X! (U -P U (]) > U +J o c U -P (U -H a tn Eh M CD OJ -P D O o> in Eh t^ O in (N LO
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151 the cervical vertebra v/as felt to be the best approximation of the dose received by the marrow in the right and left arms for the more realistic position. The values for these two subfields were re-calculated using this assumption. Phantom Dosimetry Results The results of the adult and pediatric phantom exposures are given in Tables 23, 24 and 25. The dose in mrads to the selected tissue or organ system has been norm.alized to an incident EAP of lO^^. The data were obtained from multiple phantom exposures for each patient geometry simulation. For the nine inch PA and six inch RAO adult simulations triplicate exposures were made, but in all others two were carried out. One of the duplicate infant AP radiographic experimental runs was carried out v/ith an atypical large beam dimension. The data from this run were considered to be nonrepresentative and the normalized dose indicies were calculated from a single phantom exposure run. The recorded x-ray operational character, incident EAP, tube current and potential, and measured beam size for each experimental run are shown in Appendix E.

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154 o en o

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156 cNi-ir-u-irMvocorHooino'^ (NCOrHHrHnrvliHCO ••^ iH in >H 00 o o ro G> rH CN C LD rQ CM incNJcncx)CNVD(X)c\ir-m(N a; o O -P s o U O •H CL, c

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157 r~ rj ^x> t^ o r^ 00 o^ o n r-H ro^ o r-~ c^ Lo •* '3r^£ vo

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CHAPTER VII PATIENT EXPOSURE STUDY CLINICAL PATIENT MEASUREMENTS Over a period of approximately one year the radiation exposures to 304 patients undergoing cardiac catheterization at the UF cardiovascular laboratory were measured and analyzed. The intent of this phase of the study was to: (1) determine x-ray examination characteristics as related to patient age and type of procedure and (2) to estim.ate the doses delivered to various organ systems or regions of the body. Methodology The primary radiation measurement devices employed during the clinical patient study consisted of the EAP ionization chambers attached to the fluoro/cine and radiographic x-ray tubes. In addition to recording the 2 cumulative values in the various x-ray m.odes (fluoro, cine and AP and LAT radiography) during each procedure, additional patient and examination characteristics were logged. For the patient these characteristics included age, weight, height, sex and mid-chest dimensions. Total fluoro time and, where possible, the x-ray ti.±)e potential were also recorded. 158

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159 The Philips "Maximus-lOO " x-ray generators do not have a tube potential (kVp) meter on the control. During radiographic exposures and for fluoro/cine operation with the tube current modulation automatic brightness system, the operator is required to select the tube potential. For these cases, the indicated dial setting was recorded. During the period in which the x-ray unit functioned with the tube potential modulation brightness system there vras no means to establish the operating value. In a subsample of the clinical patients, the exposures at various body sites v/ere measured v/ith TLD . No statistical selection process was used for designating this subsample, but it consisted primarily of the first patient examined each day during the monitoring period. The sites monitored were those previously used during the phantom exposures. These additional measurem.ents were performed during 62 clinical procedures which represent approximately 20% of the total patient population observed. Patients were separated into two general groups on the basis of the suspected heart disease being of a congenital or acquired nature. Individuals with suspected congenital heart problems were classified as Group I. During the catheterization procedure for this class of patients, the individual is positioned on the flat floating-top table. Fluoro and serial biplane radiography are the primary x-ray techniques employed with cine sometimes used to augm.ent or

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160 replace the serial radiographic filming. The pediatric phantom studies were set up to simulate this type of examination. Patients evaluated for suspected acquired heart disease were identified as Group IIThe majority of the patients in this group had coronary angiography and/or intracardiac angiographic procedures performed to evaluate the ventricular or valvular function. These patients were positioned in a rotation cradle during the procedures and fluoro/cine was utilized. The adult Rando phantom studies approximated the exposure conditions associated with this type of procedure. The remaining Group II patients were separated due to the difference in x-ray examination techniques used. One subgroup involved pulmonary or aortic angiography. These patients v/ere positioned on the flat table surface to facilitate use of the serial radiographic film changers. A second subgroup involved pacemaker insertion and His bundle conduction studies. During these conduction studies, the patient v;as on the flat table surface and fluorography alone was used. Results of Patient Monitoring Table 26 summ.arizes the x-ray examination factors recorded for the 30 4 observed patients. Group I constituted approximately 65% of the patients evaluated during the study. Patient age showed a bimodal distribution similar to the

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163 12 year UF pediatric profile described in Chapter II. Onethird of the 19 7 Group I patients were less than 1 year old. Twenty-four percent of the patients fell in the second high-frequency age group of 4 to 7 years. Ninety of the 10 7 patients in Group II had coronary angiography and/or intracardiac angiographic procedures. The remaining 17 consisted of five pulmonary or aortic angiographic studies and 12 pacemaker or His bundle conduction studies. For the Group I patients, radiography is seen to be the predominant method of recording being used in 9 7% of the procedures as contrasted to the 56% utilization of cine. The significance of the radiographic exposures are better illustrated by looking at the distribution of the EAP values for the two recording modes as presented in Table 27. Radiography accounted for 54% of the total incident EAP, whereas cine was responsible for 8%. The mean fluoro times varied randomly as a function of the patient age. Individual values were seen to range from a minimum of 2 min to a maximum of 54 min. The fact that the minimum 2 min time was found in the less than 1 year age group might be expected since newborns would be included in this siibgroup. If life-threatening cardiac complications are found at birth, a catheterization will often be performed during the first or second day of life. The patient's condition is often critical and every effort is made to complete the necessary diagnosis as quickly as possible.

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166 For the Group II patients examined in the rotation cradle where fluoro and cine alone are used, the mean incident EAP values were about equally divided (fluoro [46%, cine 54%]). The total mean incident EAP for patients less than 40 years old was approximately half that for the 40 and greater class. The higher values for the older patients is suspected to be related to the greater number of coronary artery examinations carried out. As a result of the multiple selective angiographic exposures that are involved with these procedures, both fluoro time and amount of cine film exposed is great. The five Group II procedures carried out using the serial film changers (pulmonary or aortic angiography) were seen to result in an incident EAP approximately twice that for the fluoro/cine cradle exposures. This increase is directly associated with the radiographic techniques. For the 12 conduction studies where fluoro alone was used, the mean exposure values v/ere 40% of the fluoro/cine cradle exposures . Results of Subsample Monitoring v/ith TLD The TLD monitored subsample consisted of 41 Group I and 21 Group II patients. In addition to the general descriptive information collected on all patients, an observers' log was kept throughout each of these procedures. The fluoro/cine and radiographic beam sizes v/ere determined so that the

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167 incident EAP values could be converted to exposure units and compared with the surface TLD readings . Body TLD sites 7 and 8 on the anterior and posterior abdomen over the assumed ovarian location and site 9 on the inner left upper thigh, used to estimate the male gonad dose, were simultaneously used on all clinical patients irrespective of sex. Group I Results The 41 Group I patients were coded as I-l through 1-41 in order of increasing age. Table 28 presents the patient characteristics for this group. T^^/enty-nine percent of the individuals were in the less than 1 year of age classification. This is in close agreement with the l/3rd value found for this age group in the total patient population group. The second peak of the expected bimodal distribution of patient age at about 6 years is not obvious due to the small number of patients monitored with TLD, Table 29 lists the patient configuration and the fluoro tim.e as well as the number of cine frames and/or radiographic films exposed during each procedure. Tables 30 and 31 give the measured EAP and TLD site measurement values respectively . Group II Results Table 32 presents the characteristics for the acquired heart disease patients. The patients have been arranged in order of increasing age and coded as II-l through 11-21.

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168 TABLE 2 8 Group I Patient Characteristics

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169 TABLE 2 8 Continued Chest Dimensions Patient

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170 TABLE 29 Procedure Setup and Quantity of Fluoro, Cine and Radiography Used for Group I Examinations

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171 TI^BLE 29 Continued

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17; TABLE 30 Group I EAP Values

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173 TAaiiJb; 3u continued

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174 tn

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176 TABLE 32 Group II Patient Characteristics

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17 7 Patients 11-20 axnd 21 have been separated from the other patients in this grouping since they were conduction studies where fluoro only was used. Table 33 lists the patient setup and amount of fluoro and cine used, as well as the measured EAP values for these modes of exposure. The individual sits TLD measurements are given in Table 34. Interccmparison o f Dosimetry Techniques Exposure measurements during clinical studies and for simulated examination conditions using human equivalent phantoms have been performed. The results of these individual measurements, carried out with EAP meters and TLD, were intercomipared to identify differences in predicted and measured value. Incident Exposure By using the measured EAP values and the TL dosimLeter readings, two independent estimates of incident skin exposure can be made. If exposure from a single fixed geometry beam is considered, a surface TL dosimeter at the center of the incidence skin surface should register the same exposure value as that estimated from the EAP measurement. Bushong and colleagues (1973) have shown this to be true for normal chest radiography. Hov;ever, during cardiac catheterization multiple beam incidences are involved. Under these conditions any individual surface TL dosimeter may ba exposed to primary, attenuated primary or scatter radiation.

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178 > < Ti (U en H o ^ tC o c M -H o e -H O C O 13 M Ol O S-J

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179 -p

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180 The beaiT\ size at the plane of the image receptor (input phosphor of image intensifier for fluoro/cine and the film plane for radiographic exposures) measured during the procedure was first converted by triangulation to the estimated position of the input skin surface. The geometry assumptions used for the various modes of exposure were discussed in Chapter II. For fluoro and cine, it v^as assumed that the external input surface of the fluoro image assembly was 5 cri from the surface of the chest. Two cm were then added to account for the distance of the plane of the input phosphor from the intensifier assembly's external surface. The measured EAP value was then divided by the area at the input skin surface and a correction for backscatter, using the data in Appendix A, was made. To evaluate the difference betv/een the two exposure measurements, the TL dosimeter reading was divided by the estimate obtained from the representative EAP measurem.ent (i.e., TLD site number 6 for fluoro/cine, TLB site nur:t)er 7 for LAT radiography, site number 4 for AP radiography) . The values for the Group I patients are tabulated in Table 35, In general, the posterior chest site (number 5) value was abou-c 80% lower than the^ fluoro/cine estimate. This would be expected since during a catheterization procedure the fluoro beam is used to aid the physician in advancement and positioning of the catheter. This may involve considerable exposure to areas other thai r^^ 4-V,„ -h,

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181 Q)

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183 For the AP and LAT radiographic exposures , the ratio of 2 the TL dosimeter to R.cra derived exposure estimate v/ould be expected to be one or greater. Except for the intravenous pyelogram (IVP) exposures that may have been taken at the conclusion of the examination, the radiographic beams would be centered over the heart with sites number 4 and number 7 in the respective primary AP and LAT beams. During two procedures (patients 1-33 and 1-41) , the TL dosimeters were inadvertently removed as a result of patient manipulation prior to completion of the procedure. The ratio of the tv;o exposure estim.ates, as identified by the footnote in Table 35, is seen to be low, as expected. The site number 4 AP values for patients I-2S and 1-30 are also seen to be lov/. For each of these procedures, two IVP films were taken. Patient 1-29 had biplane scout films taken, but serial biplane radiography was not performed in either case. The lower value for the site number 4 to AP ratio can thus be explained by the high proportion of the AP exposure during which the site number 4 dosimeter received only scatter radiation. The precision of the exposure estimates obtained from the EAP values is directly dependent upon the accuracy of the exposure geometry factors. The geometric uncertainties for the PA and AP exposures would be expected to be less than for the LAT projections. The source-to-patient distance for the under table fluoro/cine tube is fixed. For the AP

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184 the only variation that might be involved would be use of an inaccurate measurement of the mid-chest dimension, or technician error in positioning the x-ray tube at the correct source-to-image receptor distance. For the LAT exposure, the patient must be physically slid toward the lateral film changer. The goal is to position the patient as near to the changer as possible. For calculation purposes, a physical separation of 7.4 cm (9 cm from patient surface to plane of film) v/as assumed, as shown in Figure 3 of Chapter II. If, in fact, the patient is in contact v/ith the changer, the incident exposure estimate calculated from the measured EAP value for a patient with a nominal 20 cm^ lateral chest thickness would be approximately 20% high. This, in turn, would result in a similar reduction in the site number 7 to LAT ratio and may account for the ratio values less than one. Table 36 lists the incident exposure estimates calculated from the EAP value and the ratio of the posterior thorax TLD site number 6, to this estimate for the Group II patients. The mean value of the ratio for the 21 patients was found to be 0.21 which is significantly less than the Group I patient values. The primary reason for the lower value is related to the significant amount of exposure that takes place when the patient is in an oblique projection.

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186 EAP Measurements To evaluate how representative tiie exposure conditions, for the sx±igroup of clinical patients monitored with TLB's were of the similar patients in the total population group, the EAP values were compared. The comparison values are listed in Table 37. For the Group I patients, separate comparisons are made for the 21 year old and the 5 to 7 year olds because the patients in these age groups are comparable in size to the two infant and child pediatric phantoms. The mean EAP values are seen to be similar with the less than 1 year Group I and Group II data varying by 5 and 10% respectively. The Group I 5 to 7 year old TLD patients had a mean EAP 20% greater than the comparable total patient population, but these results were based on data from only four TL monitored patients. Selected Surface Sites All of the phantom exposures were carried out v/ith the x-ray beam in line with the transverse sectional plane passing through the heart; however, during clinical procedures this condition is not always met. The scanning of the fluoro beam over the upper or lower portion of the trunk of the body would be expected to alter the dose received by the eyes thyroid and gonads. To examine the possible magnitude of this effect dose indices derived from TLD measurements at these patient sites were compared with the corresponding phantom-derived dose index values.

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187 Ti^J^LE 37 Comparison of EAP Values for TLD Monitored Patients with Values from Total Pc.tient Population Patient Classification AdultGroup II (in cradle) Number of Patients Total EAP [^) Mean (range) 1 Monitored with TLD 2 All in group 19 90 3,552 (1,0429,982) 3,951 ( 437-11,079) Child-Group I (5-7 year) 1 Monitored v/ith TLD 2 All in group 2,069 (1,3402,965) 1,643 ( 1393,249) Infant-Group I (<1 year) 1 Monitored with TLD 2 All in group 12

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188 As in the EAP comparison, patients in the less than 1 year and 5 to 7 year Group I classification and Group II patients examined in the rotation cradle were used for this evaluation. Using the fluoro, cine and AP and LAT radiographic EAP values and allocating between various fluoro and cine modes, a weighted phantom dose index value v/as obtained for each of the organ systems. For the adult phantom values, the fluoro PA and oblique geometries were weighted equally; whereas for the cine, the oblique projection was assumed to be used 75% of the time. Fluoro v;as divided equally between the nominal six and nine inch modes, but cine was assumed to be carried out in the six inch mode exclusively. For the child phantom, fluoro and cine was weighted equally between the six and nine inch modes. The results of this intercomparison are shown in Table 38. In all but two cases the patient and phantom dose indices varied by no more than a factor of approximately two. The measured patient values for the infant thyroid and adult lens of eye are seen to be higher than the phantom-derived values by factors of three and five respectively. For the infant thyroid site the variation is assumed to be due to its close proximity to the edge of the primary beam. The probability is high that during clinical procedures this site will be in and out of the primary beam. The variation for the adult lens of eye estimate may be due to the difference in geometry for the phantom and patient. The

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K ! 189

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191 position of the '^hantoin. head is fixed. When placed in the cradle, the longitudinal axis of the skull is in line with the horizontal axis of the cradle and does not duplicate the adult patient position. During clinical studies the patient's head is propped up with a pillow. This elevated position places the forehead site, used for the lens of eye measurement, closer to the source of scatter. Attenuation provided by the nose or other skull tissues would also be expected to be less for this patient position. The absolute value of the dose to the eye is small in comparison to the quantities that are significant in cataractogenesis so the variation betv;een the mieasured patient and phantom-derived predictions is not critical. The phantom-derived dose indices were judged to be sufficiently comparable to the indices obtained from, the clinical patient measurements to justify using them with the EAP values as a practical means of evaluating the magnitude of exposures during cardiac catheterization. Population Predictions By reviev/ing the differences in types of cardiac catheterization procedures in combination with the variation in patient description, it can be seen that the calculation of typical exposure values is difficult. Accurate dose estimates can only be made on a patient-by-patient basis where the individual factors can be appropriately accounted for.

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192 Although these limitations are recognized, the phantomderived dose index values have been utilized in conjunction with the typical examination conditions observed in the UF cardiovascular laboratory to estimate mean and limit values. •These values are given in Table 39 . For the Group I patients the total EAP value was assumec to be equally sp].it between fluoro/cine and AP and LAT radiography. For the 5 to 7 year old patient group the fluoro/cine operation Vv-aE equally divided between the nominal six and nine inch modes. The image intensifier was operated exclusively in the six inch mode for the less than 1 year old patients. The contribution from fluoro and cine for the Group II patients examined in the rotation cradle was assumed to be equally divided. The fluoro EAP contribution was equally divided between the PA and oblique geometries for the two intensifier modes of operation. All cine v/as assumed to be carried out in the nom.inal six inch mode with the oblique projection used 75% of the time. The body surface exposure estimates were based on the subsample of patients monitored with TLD since accurate beam size information was available to facilitate conversion of EAP to exposure units. The integral dose \^alues were obtained using the EAP conversion factors developed by Carlsson (19 6 3) as described in Appendix F.

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19 3 0)

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19 4 The mean EAP values are seen to incx-ease with patient age with the value for the adult Group II patients being 4.3 times that reported for the Group I patients less than 1 year old. This increase is, in turn, reflected in the mean patient surface exposure which increased from 15 R for the infanr to 57 R in the Group II adults. A maximum body surface exposure of 171 R was determined for an individual in the Group II TLD monitored subgroup. This exposure value was determined from the EAP reading, and it must be kept in mind that since the patient is rotated during the examination no individual surface skin site would be expected to receive this total amount of exposure. For the smaller pediatric Group I patients the primary beam(3) intercept a greater portion of the total body surface than for an adult. The maximum, skin exposure would thus be expected to more closely approach the estimated surface value. Although EAP and incident surface exposure values were observed to increase with patient age, all other organ doses decreased. This is directly related to the increase in patient size with age and the resultant decrease in the number of critical tissue sites in or in close proximity to the primary beam. In all cases the bone marrov; received the highest dose and must be considered the critical dose-limiting organ system. Of second importance is the thyroid. The phantom estimated infant thyroid surface dose (anterior neck skin surface) was

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19! shown to be approximately one-third that measured in a limited patient sampling. If this correlation accurately reflects the general situation, the thyroid exposure to the young child may be highly significant. The ovarian dose was found to be greater than the male testicular value. Comparison with Other Published Data Table 40 summarizes patient radiation exposure values reported by various authors. Detailed comparitive analysis is difficult due to differences in patient populations, equipment dosimetry and procedural techniques. The range associated v/ith all the reported data is seen to vary widely as the values did in the UF patient study. Comparison of the various reported mean values with the UF data shows general agreement v/ithin an order of magnitude. In spite of the unquantified differences in patient, equipment and techniques that exist from facility-to-facility, the comparability suggests that the results of this study could be used to make preliminary dose estimates for a wider sampling of cardiac catheterization patients.

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196 0) rH 0! > c (1) — O r3 a, T!

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19 7 a) > G m (U •— -4-) M C O fO e E S E S o r-

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CHAPTER VIII SUI-^MARY AND CONCLUSIONS Detailed radiation studies in the UF cardiovascular laboratory and field surveys in other Florida facilities have confirmed the anticipated high potential for significant radiation exposure to patients and personnel involved with x-ray cardiovascular special procedures. Personnel Exposure Personnel monitoring records for 38 physicians and 45 technologists associated with 10 Florida cardiac catheterization facilities were reviev/ed. The locations of the primary monitoring badges were about equally divided between ovei" and under apron positions. Four physicians were found to use duplicate badges so that values for both sites could be determined, but single monitoring sites were used exclusively by the technologists. The yearly mean dose equivalents at the under apron site were 184 and 251 mrem for the physicians and technologists respectively. At the over apron position the yearly mean values were 1,376 and 625 mrem. The ratio of the shielded to unshielded value is seen to be significantly different v/ith 198

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199 a value of 7.5 for the physicians and 2.5 for the technologists. This variation may be related to differences in the lead equivalent thickness of the protective aprons worn by the two groups, or variations in v/orkload and procedural duties for the individuals utilizing the respective badge sites. Due to the limited sample population and method of information retrieval, the reason for this difference could not be determined. In Chapter IV, the published data reporting estimated occupational exposure levels were reviewed. Klement and colleagues (19 72) listed mean values for medical x-ray workers in the U.S. ranging from 83 to 320 mrem/year. The United Nations Scientific Committee (19 72) reported a similar range for world-wide medical x-ray workers of 70 to 380 mrad/year with the U.S. estimate as 340 mrad/year. These values were based on personnel exposure records, but no information regarding the badge site was given. If it is assumed that similar under apron and over apron practices exist for medical x-ray workers in general, as was observed in the ten Florida cardiac catheterization facilities, the mean exposure for this subpopulation can be com.pared to the U.S. mean values. For the Florida sample, the estimated yearly exposures from the unadjusted personnel monitoring records are 723 mrem for physicians and 417 mrem for the technologists. If the assumptions are correct, these values suggest that

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200 exposures to cardiac cat±Leterization v/orkers may be as much as twice that of medical x-ray workers in general. Detailed personnel exposure measurements were carried out in the UF cardiovascular laboratory. The exposure received by physicians conducting adult patient studies was at least twice that received by physicians involved with pediatric examinations. The lens of eye and thyroid were found to be the critical dose-limiting sites. The lens of eye was also shown to be the critical tissue for the technologists. On a per procedure basis, the technologist generally receives less exposure than the physician. When the individual procedure values v/ere converted to anticipated yearly estimates by taking into account typical personnel workload factors, the lens of the eye value for the technologist was slightly greater than for the physicians. Based on the significant potential for high exposures to personnel during cardiac catheterization, radiation safety is an important consideration in the setup and operation of a laboratory. The input of a medical or health physicist should be included during the initial planning and operational phases . The layout of the procedure room and configuration of the x-ray source(3) and examination table are of key importance. Appropriately designed protective shielding must be used by all personnel. A wrap-around apron that also

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201 provides shielding to the neck (thyroid) should be used. Since the eyes were shown to be the critical dose-limiting organs for both physicians and technologists, the use of some type of high-density glasses may be appropriate. For the physician and technologist working in close proximity to the patient, the use of two monitoring badges is recommended. One should be located at the head or neck level at a position external to the lead apron (a site on the collar or shoulder nearest the patient is recommended) . The second badge should be positioned on the hand or wi^ist. The exact location of the badge should be established in relationship to the anticipated scatter radiation contours around the examination table and the position of the personnel during the procedure. The recommended site m^ust be clearly understood by each individual and should be recorded as part of the personnel exposure record. P atient Exposure Dosimetry studies using phantoms and clinical patients examined in the UF cardiovascular laboratory were carried out to investigate the dose to various organ systems including the gonads, bone raarrov.', thyroid and lens of the eye. The bone marrov; v/as found to receive the highest dose in both adult and pediatric patients and may be considered the critical organ system of interest with relation to somatic

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202 effects. For the pediatric patient, the dose received by the thyroid may also be of concern. The ICR? (19 73) has identified the examinations for coronary arterial disease as a protection problem of current concern in which very high exposures are to be expected and maximum effort needs to be continuously exerted to ensure that exposures in these examinations are no higher than necessary. They recommend that the fluorc, cine and radiographic exposures utilized in these procedures be recorded. The use of EAP measureraent systems offers a practical approach to this measurement problem. The value determined with these instruments can be easily converted to surface exposure or integral dose values. Through the use of phantom-derived dose index values, the measured EAP values can be related to selected organ doses. The majority of cardiac catheterization examinations performed involve adult coronary angiographic procedures. The significance of the radiation exposure in these procedures must be evaluated with respect to the patient's age and life expectancy. The majority of the patients suffering from coronary artery disease are beyond the reproductive age and the genetic consequences of the radiation exposures are usually of minimal concern. The potential for somatic effects must also be viewed in relation to the less-thannormal life expectancy for this class of individual.

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20. At the present time statistical descriptions of the adult cardiac catheterization patient population are not available but would be e^xpected to be heavily weighted in the older age groups with advanced coronary complications. As the nuinber of trained personnel and cardiac catheterization facilities increase it is likely that a younger patient population, whose genetic and life expectancy'' is significantly different from that presently seen, will be routinely examined. The possible catheterization of asymptomatic subjects in certain occupational areas, such as airline pilots, has also been suggested. The efficacy of these examinations must be questioned. For the pediatric congenital heart patient the situation may be quite different. Individuals in this group are often catheterized at a very young age and the frequency of recatheterization, as obsei'ved in this study, is higher than for the adult acquired heart disease patient. V7ith the advent of ne;; and more successful surgical techniques many of these patients will have normal life expectancies. In this situation the genetic and somatic consequences are of paramount concern . Xr ay E q u i PqjgIlt_A^lt ern a t i ve s Radiation protection for the patient ^indergoing a cardiac catheterization examination involves acquisition of the necessary diagnostic information with the minimum

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20^ radiation exposureThe two areas where this minimization can be achieved are in the examination techniques used bv physicians and the configuration and exposure characteristics of the x-ray equipment. These areas are closely interrelated; the examination procedure may be dictated in a large degree by tlie characteristics and limitations of the equipment. In the equipm.ent area, every advantage must be taken of new technology. In cardiac catheterization, the use of intermittent pulsed fluoro and fluorography as a substitute for serial radiographic procedures appears promising. Pulsed Fluoroscopy During cardiac catheterization, fluoro is used as a visualization technique to assist the physician in placement and manipulation of the indwelling catheter. The diagnostic information is primarily derived from the angiographic, hemodynamic and electrocardiographic procedures. Therefore, during the fluoro visualization phase the information content provided by the normal television setup utilizing a double interlaced 30 Hertz (Hz) frame (two fields) rate may be much more than is required by the physician who is only interested in knowing the position of the catheter. Pulsed fluoro systems utilizing video disk recorders or image storage tubes have been proposed for applications of this type. Dorph and colleagues (19 70) and Grollman and colleagues (19 72,19 74) have reported on video disk systems. The unit

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205 described by Grollman vvas utilized for adult cardiac catheterization studies. In the Grollman system, the video disk recorder was operated in a synchronous fashion with a grid-controlled x-ray sourceDuring the l/60th of a second associated with one field of the double interlaced television display, the x-ray source is gated on and the resultant image stored on the video disk recorder. The disk which is rotated at 60 Hz can be played back each l/60th of a second so that a continuous display is viewed on the monitor. Since only one field of the usual double interlace display was used, a 945 line television system was substituted for the standard 525 line system to increase vertical resolution in this system. With the Grollman system the operator could select the desired pulse rate over a range of 15 to 15/16 pulses per second. Operation at 15 and 7-1/2 fields per second have been used during cardiac catheterization. At 15 fields per second, no loss of continuous smooth movement can be seen on the monitor; whereas, at a frequency of 7-1/2 fields per second some loss is apparent. Grollman states that no objection was found at the 15 per second rate and only a few physicians expressed concern over the fact that they thought they might be losing some required information at the 7-1/2 per second rate. During actual clinical studies, Grollman states that the use of this technique did not result in any

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206 increase of the overall fluoro tiine necessary for an adult catheterization procedure and he found a typical reduction of overall patient exposure of 50%. A theoretical evaluation of the degree of exposure reduction that can be achieved by use of a pulsed fluoro system has been reviev/ed by Siedband (19 73) . He contends that if the f luoroscopists require the same image quality in pulsed mode operation as that obtained during continuous real time fluoro, no dose reduction can be achieved for pulse rates faster than five per second. This prediction is based upon a typical integration time for the eye of 0.2 seconds. For an image of equivalent quality (i.e., equal signal to noise ratio) the same amount of quantum information must be present in a single or series of multiple fram.e images. If this conclusion is correct the pulsed images available from the Grollman system, which were obtained at rates faster than the five per second limit, would have been expected to be of reduced image quality. This, in turn, may indicate that during the fluoro portion of a cardiac catheterization examination a pulsed image with some reduction in image quality is acceptable. The design of a pulsed image system for use in cardiac catheterization might logically em.ploy a lead oxide TV tobe used in conjunction with, a video disk recorder operating in a field (one-half interlaced frame) storage replay mode. The lead oxide TV tube is superior to a vidicon since it can be

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207 read out after the second observed field (l/BOth second) as opposed to a required three or four fields for the vidicon. The half frame, field storage node of operation v/ould also seem more logical for this application where resolution is not of primary importance. Although vertical resolution would be lost by vievring a single field as compared to full frame viewing, a savings in exposure is realized. The problem of interframe jitter that can exist with full frame replay of a moving object will also not be present in the field mode of operation. Although it can be expected that some decrease in patient exposure will result from utilizing pulsed fluoro, an accurate prediction cannot be made. The limits to which image quality and pulse rate can be reduced must be established under clinical situations. Grollman's v/ork indicates that operation at 7-1/2 fields per second v/ith an assumed reduction in image quality is acceptable during adult cardiac studies. If these values represent the minimum for adult studies and if these same conditions are applicable to pediatric congenital heart studies is presently unknown. Although a considerable number of unknowns exist, a predicted reduction in the fluoro exposure by at least a factor of two seems within reach. This value is consistent witJi operation at 7-1/2 fields per second with a times two boost in the exposure rate to partially compensate for the loss in signal-to-noise ratio associated with the pulse mode operation.

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203 Flu Q rograph.y A second area where an equipment change may result in a reduction of exposure would be the substitution of fluorographic techniques for the serial film techniques usually employed in congenital studies. Fluorographic techniques typically utilise a 70 or 10 5 mjti camera coupled to the x-ray im.age intensifier. The exposure per frame of information required for operation in this mode is less than that required for conventi.onal rc.diographic film. The actual difference in exposure bety.'een the two methods depends on a number of factors which include the conversion efficiency of the intensifier and optical chain, as well as the field size; film type and development scheme. Carlsson and Kaude (1968) state that a 70 rvm fluorograph required approximately 12% of the exposure of that for a full size radiograph taken with m.edium-speed screens and high-speed film. For a 105 mm fluorographic cam.era adjusted for 100 micro R per frame at the intensifier input (external input surface of image intensifier tube) , Maddison and Handel (19 74) report the fluorographic system required an exposure level 20% of that necessary for radiographic exposures in a serial film changer. Kaude (19 6 7) has discussed the potential of dose reduction by use of 70 mra fluorography in a num.ber of selected radiographic procedures. He and co-authors have reported on the use of this technique as compared to other modes of

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209 filming during hysterosalpingography , gastrointestinal examinations and voiding urethrocystography (Bang and Kaude (1967), Carlsson and Kaude (1968), Kaude and Reed (1969) and Kaude, Lorenz and Reed (1969)). Although DeVilleneuve (19 73) has discussed his use of 70 nim fluorography for congenital heart studies at his institution in the Netherlands, the use of 70 mm techniques for congenital heart studies in the U.S. has not as yet been accepted. Certain restrictions, such as film size and limitation of resolution of the 70 mm format when compared to conventional serial radiographic films may be the reason. The larger 10 5 mm cameras now available may answer some of the objections associated with the 70 mm. To carry out an angiographic study with the serial radiographic film changers, the catheter is first positioned at the desired site v/ith the aid of fluoro. The patient must than be moved over the serial changer for the angiographic exposure. Since fluoro can no longer be carried out the physician has no means of knowing if the catheter is still at the desired site or has unknowingly been shifted out of position during the patient repositioning procedure. The adequacy of the examination can only be determined following the developm^ent and viewing of the films. If fluorography techniques were used, the patient v/ould not be required to be moved and the status of the catheter could be determined up to and during the actual angiographic injection. By this procedure the possibility of achieving the desired results

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210 during the initial angiographic series is increased. An immediate evaluation of the adequacy of the diagnostic results can instantly be determined. If the catheter was m.isplaced during the injection phase, the x-ray exposures could be terminated and not allowed to go to completion as is the usual case with a programmed serial changer. Serial film changers are usually equipped with a programming device which allows the operator selection of the rate and number of films that are to be exposed during an angiographic series. The programmer is provided to overcome the inherent limitations of the changers relating to the maximum number of films that can be loaded at one time. Secondarily, limitation of heat loading of the x-ray tube and reduction of exposure to the patient are also achieved by use of the programming device. During pediatric congenital heart studies carried out in the UF cardiovascular laboratory biplane serial radiography is the primary mode of filming. An acceptable amount of inform.ation is presently obtained using Elema Schonander cut film changers. These changers, which hold a of 30 films, can operate at rates up to six films per second. During an angiographic study the programmer is usually set so that the changer is operated at the maxirjum rate of six frames per second during the initial tv/o or three seconds vi-hile the bolus of contrast media is concentrated in the site of interest. Following this initial phase the films are

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211 exposed at some reduced frequency. During actual procedures, it is rarely necessary to ;itilize th.e full capacity of the changers. Eighteen to 2 2 films per changer are usually sufficient. Presently fluorographic cameras are not equipped with similar programming capabilities. The operator can select various frame rates , but once the camera is in motion this setting cannot be changed. The on-off initiation of the exposure is usually controlled by an operator foot switch. A fluorographic camera such as the General Electric 105 mm unit v/ill hold film sufficient to expose 40 and can operate at rates up to 12 per second. The possible dose reduction that might be achieved by substitution of this m.ode of for a serial film changer could not successfully be achieved by operating at a fixed frame rate with manual exposure control. A programming device used in conjunction v^ith a grid controlled x-ray source would have to be developed. Application of Predictions to Patient Data The predicted performance characteristics of the pulsed fluoro and 10 5 m.m. fluorographic systems have been applied to the patient dosimetry data to estimate the expected overall reduction in patient exposure that might be achieved. The pulsed fluoro system was assumed to result in a reduction of exposure by one-half. For the 10 5 mm fluorographic camera the factor of five reduction specified by Maddison and Handel

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212 has been used. The results in Table 41 shov; a reduction of approximately 63% for the Group I congenital studies. For the adult Group II patients a 25% reduction would be expected for studies such as coronary angiography. The 10 5 min fluorographic v/ould not be expected to be used for adult pulmonary or aortic angiographic studies. A reduction of 13% would, therefore, possibly be expected to be achieved in this type of examination by using pulsed fluoro. During conduction studies fluoro only is used. The exposure reduction is thus directly related to the performance of the pulsed system. Radiation Protection Criteria for Cardiac Catheterization Facilities The Inter-Society Commission on Heart Disease Resources (ICHD) has pi±ilished recommendations regarding the optimal setup and operation of a cardiac catheterization-angiographic laboratory (ICHD, 1971). The ICHD is still active and through its radiological study group a revision of these recommendations are currently near completion. The following recommendations, drawn primarily from the observations and findings of this study, were prepared for inclusion in the revised comirdttee report.^ ^Prepared in cooperation with Dr. Larry P. Elliott, Cardiovascular Radiologist, University of Florida. Dr. Elliott is a working member of the ICHD radiological study group.

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213 CO O ^ >i c Xi (a o c u o 0) •H Ci +j "— u P 0) « -a u o 3 o to E-" O X 0) m in -H (b o -P 0) o a •H ca -a jDiHO>'*ooo'=iM U -a) 4J O w ffi M-s. O O en o =3 --^ X! <~\ H CH 0) CN "O 4-1 ^ 01 in 4J iH • -H 13 r-^

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214 '-H

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215 Equipment and Facility Design The x-ray equipment and procedure room should be designed and maintained to meet accepted radiation protection criteria (NCRP, 1968 and 1970; ICRP , 1970). Many of these requirements will be met for x-ray systems manufactured after August 1, 19 74 under the Federal performance standards for diagnostic x-ray equipment (42 CFR 1020-30,31,32). Every attempt should be made to upgrade older systems not covered by these requirements . In addition to the requirements consistent with accepted radiological health criteria for diagnostic x-ray installations, as outlined in the aforementioned references, the follov^ing aspects are considered of particular importance for cardiac catheterization laboratories. Beam limitation for fluoroscopy, cine and spot film fluoro graphy The x-ray equipment shall be designed to allov; x-ray production only when the primary beam is alligned and completely intercepted by the image intensifier for fluoro and cine. The primary physician and assisting personnel should never be positioned so that any portions of their bodies intercept the primary beam. Consequently, the major source of exposure to all personnel within a catheterization laboratory is secondary or scattered radiation. The following are suggestions regarding equipment design for primary beam limitation and protection of personnel from scattered radiation.

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216 Primary beam . AdjustaJ^le triple-leaf beam-limitation devices (collimators) v/ith. or without additional cones to limit the x-ray field should be utilized. If the fluoroscopist requires visualization of the entire circular image produced by the intensifier, a circular beam-limiting device should be employed. The beam-limitation system, should be designed to limit the primary beam to no greater than the dimensions of the visible image. When the x-ray tube image intensifier combination allov/s independent movement of the image intensifier and/or x-ray tube, the unit should be designed so as to limit the field size at the plane of the intensifier input phosphor to no greater than the dimensions of its visible image. On units equipped v/ith a dual or triple mode intensifier, the beam shall be automatically limited to the dimensions of the particular mode in use. Scatter . To reduce scattered radiation from, the under table tube to as low a level as possible, the following criteria should be followed: a. For units with an under table x-ray tube and over table image intensifier, shielding should extend up along the sides of the table to the edge of the table top. In the advent of an add-on cradle which positions the patient above the table surface,shielding should extend up to the cradle edge. In most laboratories with add-on or portai)le cradles, this form of shielding is not in current use. The elevated position of the add-on cradle

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217 creates an exit port allowing back or side scatter radiation to strike the hands and mid-body region of any person adjacent to the table. The floating-top table surface, which is not used for patient support when a cradle is in use, also increases scatter, which in turn reduces image quality. To maintain the rotational cradle concept, yet abolish the air gap, a table with interchangeable tops should be utilized. b. Caution should be exercised in the use of equipment of the so-called Cor U-arm configuration. In this unit, the patient remains horizontal v;hile the xray tvbe and intensifier are moved in an arc around the patient. Scatter shielding is difficult to adapt to a unit of this type. As a result, the degree of scattered radiation to operating personnel is high. Limitation of use may be the only acceptable means of maintaining adequate personnel protection. c. An installation v/ith over table x-ray tube and under table intensifier shall not be used. d. A detailed determination of isoexposure levels around the x-ray unit shall be made to establish the optimal position for operating personnel. Scattered radiation levels should be obtained with a phantom which approximates the geometry of a typical patient. For personnel required to rem.ain in the room during fluoro or filming, these data will establish areas of

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21? minimiii-n exposure. In addition, design and placement of monitoring equipment, etc., should be made based upon knowledge of these scatter levels. e. A shielded control room should be included as part of the installation. This should house the main x-ray controls, physiological monitoring equipment, and any other items (i.e., scriob sink) v/hich are nonessential to room. use. Mechanism for primary ptiysi c ian to moni tor operational status of x-ray system The x-ray system should be designed and installed so that the physician conducting the examination can determine the operational status of the fluoro/cine imaging system (s) throughout the entire procedure. Of primary importance is an indication of the brightness level of the im.age intensifier and the heat loading status of the x-ray tube. The brightness level indication will assure him that the cine films are being exposed to a light intensity consistent with adequate film recording. Knov/ledge of the moment-to-moment heat loading status of the x-ray tube and housing will allow him to carry out the procedure v/ithin the restraints posed by the x-ray equipment. Of slightly less importance, a.lthough highly desirable under ideal conditions, is a system that will provide an indication of the technique factors such as x-ray tube \'oltage,current or pulse v^idth which is varied automatically by the

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219 x-ray unit or that is required to be adjusted irianually to achieve an adequate brightness level. These indications should also be located so that the physician conducting the examination can see them from his usual operating position. Dose reduction in relation to mode of imaging Whenever possible a mode of x-ray examination consistent with acquisition of sufficient diagnostic information with the mdnimal radiation exposure should be utilized. Examples of possible choices include: 1. Video disk pulsed fluoro. 2. Cine film and radiographic film-screen combinations which require minimum radiation exposure. 3. Substitution of 105 mm fluorographic techniques for situations where large film seriographic techniques were ordinarily used. 4. Limitation of cine frame rate to the minimum necessary to obtain the necessary diagnostic inform.ation. Fluoroscopic tim .er A cumulative fluoro timing device shall be provided as part of the x-ray control. This device shall indicate the status of fluoro time by an audible signal emitted at tim.e intervals of 5 min or less. The timing unit shall also provide a total cumulative time for" an entire procedure. Indication of this total cumulative tim.e sxiould be visible to the physician performing the procedure.

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220 Method of quality contr ol of th e radiologic facility All cardiac catheterization facilities shall be evaluated by a qualified radiological physicist. 1. In the case of a new facility the physicist should be involved during the planning stage. Following installation a complete radiological evaluation shall be performed prior to patient studies. 2. In the established laboratory, periodic evaluation of the radiographic facility at time intervals of six months or less should be made. There are numerous equipment functions that should be periodically evaluated. Those such as the interlocking between the x-ray tube and image intensifier are usually straightforward. On the other hand, slow deterioration of the image intensifier systemi may go undetected. With the latter, this miay involve two m^ajor areas: (a) a decrease in quantum conversion efficiency requiring a higher incident x-ray level to achieve the necessary output brightness (more radiation) and (b) a reduction of image resolution capabilities which reduces tlie quality of diagnostic information available (i.e., radiation adequate, but intrinsic defect in imaging capability of system) . Periodic testing of these systems will identify these changes.

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221 3. Following manufacturer service adjustment or replacement of components (x-ray tubes, intensif iers , etc.) a check of system performance should be made. Examination and Operational Techniques Apart from the design and installation of the x-ray equipment and facility, reduction of exposure to patients and personnel can only be assured through certain precautions associated v/ith the examination and operational techniques. Personnel Radiation monitoring . For occupational exposed personnel, yearly exposure limits are established (Table 42 lists the maximum annual permissible dose equivalent values for occupational exposures to various parts of the body) . A maximum exposure of 5 rems/year for whole body exposure is specified. The lens of the eye, gonads and red bone marrov; are considered the critical organs for this whole body limit. For an individual wearing a lead apron, the gonads and the major portions of the red bone marrow are shielded, resulting in the eyes being the critical limiting organ. In addition, the next most sensitive portion of the body that is not covered by the lead apron is the thyroid, which has a yearly limit of 15 rem. A personnel monitoring device, film or TLD badge, should be worn by all personnel. This monitor should be located at the head or neck level at a position external to the protective lead apron.

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222 TABLE 42 Occupational Dose Limitation Recoimnendations Suggested by the NCRP Prospective Annual Limit^ Portion of Body Exposed (r em/year) Whole Body 5 Including lens of eye,gonads and red bene marrow Skin 15 Unlimited areas other than hands and forearms Hands 75 Forearms 30 Other Organs, Tissues and Organ 15 Systems (i.e. , thyroid) For the physician and technician working adjacent to the patient, an additional hand or wrist monitor should be worn. The proximity of the hands and arms to the patient and

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223 primary beam can result in high e>:posure . If exposure levels for these hand positions are shown tc be consistently lov? their day-to-day use may not be necessary. To check on changes in technique and habit patterns , periodic rechecks (for example, every six months) should be carried out to reconfirm the acceptable low levels of exposure at these sites. In addition to maintaining a log of measured personnel exposure levels an indication of the site of measurement should be included as part of the permanent record. Design of lead apron . The choice of letid apron design should be based on a knowledge of the work habits and tasks required of the wearer. For instance, if an individual is frequently positioned with his back to the patient, a full wrap-around design should be utilized. Although a separate waist apron worn on the back would provide some protection, it is not considered as acceptable as the single wraparound design. The v/aist apron covers only the lower portion of the back and cannot be expected to be worn as consistently as the all-in-one v/rap-around design. For the physician as v/ell as the personnel working in close proximity to the patient a . 5 mm equivalent lead apron should be worn. For those circulating in and out of the room., a 0.25 mm lead apron is usually adequate. Posit j-on of personnel durin g x-ray . During radiographic procedures all personnel shall be behind a protective barrier. During cine fluorography auxiliary'personnel not directly assisting the physician, shall step back away from the

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224 procedure table and preferably behind a protective barrier. Neither the physician nor auxiliajry personnel shall directly hold the patient for x-ray positioning purposes. The physician conducting the examination should acquire the habit of verbally alerting the members of the examination team as to his intent to initiate fluoro or cine exposures whenever an individual is in a position v/here high exposure rates exist. Situations of particular concern exist when an individual with unprotected portions of his body m.ight be present in the room. This could be an individual scrubbing in preparation to assist in the procedure with his back to the patient or any other individual in the room carrying out some task that does not allow him. to keep in moment-tomoment contact with the physician's conduct of the examination. To prevent an individual from receiving an inordinate amount of radiation exposure, the various duties dealing with x-ray should be on a rotational basis. Patient exposure Patient exposure records . A record of fluoro time, as well as each separate mode of recording should be maintained. This can be done by recording the x-ray technique factors, kVp, mA and pulse width, etc., in addition to total time for fluoro and feet of cine film. If seriographic or fluorographic exposures are made, the x-ray techniques utilized and the number of films exposed should be recorded. Therefore, a

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22[ calculation of patiant exposure can be made utilizing the aforementioned factors along with a knowledge of the output cf the x-ray machine. Because this type of data retrieval is laborious and time consuming, the use of a Roentgen-area-product ( ) meter can be made. This device utilizes an ionization chamber mounted on the distal end of the x-ray beam-limiting device (collimator) and has a remote readout that v/ill integrate the area exposure product for an entire procedure. A dual register readout can be used to automatically separate the fluoro and cine exposures. The initial installation and format for measurement should be established v/ith the consultation of a radiation physicist. Dose to reproductive organs . Whenever possible the gonads should be excluded from, the primary beam. For patients who are capable cf reproduction, the use of gonad shields should be used if the primary beam v/ill intercept the reproduction organs . a. For adult patients of reproductive age v/here the gonads are greater than 5 cm from the edge of the primary beam, gonad shielding may be of limited usefulness (Bureau of Radiological Health, 19 74) since scatter originating in the patient will be the major source of gonad exposure. Among females, external body shielding is of little use in reducing ovarian dose. In m.ales only a male gonad shield which isolates the testes v/ill

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226 be effective. As a practical guide, unless other patient information indicates the contrary, persons above age 45 years need not be considered candidates for gonad shielding. Statistics show .that over 95% of all babies in the U.S. are born to parents of age 45 or less. b. The 10 day rule (ICRP, 19 69) should be applied to female patients of reproduction age. This rule v/hich calls attention to the embryonic and fetal sensitivity to ionizing radiation, states that all radiological examinations of the lower abdomen and pelvis of women of reproductive capacity that are not of importance in connection with the immediate illness of the patient, be limited to the period when pregnancy is improbable (the 10 day period following the onset of menstruation) . Although cardiac catheterizations are not lower pelvic examinations, the high exposures and occasional visualization in the lower abdomen that are often associated with these procedures, makes it appropriate to apply this rule. c. For pediatric patients, gonadal shielding should be utilized. Even if the gonads are not in the primary beam, the position of the reproductive organs with respect to the primary beam wi'll be much closer than for the adult patient. Every -attempt should be made to reduce this unnecessary exposure.

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227 Identification of film . The marking of cine film with patient and . institution identification inform.ation should be done without the patient in the beam. Cine quality control Maintaining quality control in all x-ray systems is the touchstone for obtaining the optimum amount of inform.ation with the least amount of radiation. In the area of cine, a routine evaluation of each of the facets of system performance should be made. Because of the complexity of the many varied components forming the cine imaging system (i.e., from generators to ultimate method of viewing) , it is not feasible to check each component on a daily basis. The tv;o major areas that are most subject to variation can be evaluated on a day-to-day basis. These are the conglomerate aspects (x-ray source, image intensifier, automatic brightness system., cine cameras and optical chain) of the exposure phase, and the film development phase. A test of cine operation should be made at the start of each day. Ideally, this includes subjecting tv/o strips of cine film to the following: (1) an x-ray exposure made utilizing a suitable test object, and (2) a film strip exposed with a regulated light sensitometer . The variation in the x-ray exposed strip would indicate problems in either the cine exposure system or development phase. Whereas,

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228 variations in the sensitometer exposed strip can be isolated to processing problems alone. In addition, it is recommended that a test phantom be included as part of the cine identification frames which are exposed to identify each roll of cine film. This procedure would provide an examination-by-examination index of system operation which may be useful in evaluating the long term operational status of the equipment.

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230 APPENDIX A During biplane serial radiography the Philips "Maximus100" x-ray generators were operated in the falling load mode. For pediatric radiography, the exposure time was set at 16 msec and the t^ibe potential varied to achieve the desired exposure value. Figure Al shows the variation in indicated mAs as a function of the kVp selector setting for operation in the falling load m.ode . Figure A2 shov/s the measured free air exposure at a source-to-chamber distance of 73 cm. This distance corresponds to the skin surface of a patient with a 14 X 16 cm AP and LAT chest dimension positioned on a pediatric restraint board (additional geometric factors are diagrammed in Figures 1 to 3 of Chapter II. Inverse square corrections must be applied for other source-to-patient distances . Figures A3, A4 and A5 give table top exposure values from the under table fluoro/cine tube. Measurements were made on the flat table surface, at the surface of the pediatric restraint board position on the flat table surface and in the cradle. Data were obtained with and without a 15 cm thick water phantom to evaluate the effect of backscatter. A].l values v/ere measured at a tube current of 1 mA. A linear correction can be applied to determ.ine the output at other tube current values.

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232 +J (D

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233 0) u w o a. X • W CD _ Xi 'd :3 0) E^ =: >i CO (0 CD I uxui/H 'aiva annsodxa

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234 ir o

PAGE 255

235 a

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236 The backscatter factor is a function of the beam size and quality of the radiation. During fluoro and cine radiography the beam size is usually restricted to the dimensions of the visible area of the input phosphor of the image intensifier. The variation in beam size during this mode of viev/ing will thus be much less than experienced during radiography. The variation of backscatter for fluoro and cine operation has thus been determined for a single beam size as a function of x-ray tube potential. The effect of backscattei for the three patient examination positions is shown in Figure A6 . The values for the pediatric restraint board and for the cradle are seen to be similar and greater than those determined at the flat table surface. This difference is primari3.y due to the change in backscatter associated with the increased effective energy of the beam for the cradle or restraint board configuration (see Chapter II, Table 5 for HVL values) . Backscatter values for the serial biplane procedures were obtained from values p\±)lished in the British Journal of Radiology ( BJR ) Supplement number 11 (1972) . The values given in the BJR report are for circular fields. These data can be used for rectangular beam geometries by first determining the equivalent diameter for the respective rectangular field. Figure A7 shows the values for square fields obtained by this method.

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237 H x^ cu

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238 -\v

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240 TABLE Bl Age Distribution For Cardiac Catheterization Patients Less Than 18 Years Old Examined in the UF Cardiovascular Laboratory Age

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241 TABLE B2 Age Distribution For Cardiac Catheterization Patients 18 Years Old or Greater Examined in the University of Florida Cardiovascular Laboratory Age

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242 TABLE B2 Continued Age

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243 TABLE B3 Recorded Fluoroscopy During Cardiac Catheterization For Adult (A) and Pediatric (P) Patients in the University of Florida Cardiovascular Laboratory

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244 TABLE B3 Continued

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245 TABLE B3 Continued

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248 c <-i

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249 TABLE C3 Experimentally Determined Reduction in TLD-100 Sensitivity Read on Eberline TLR-5 and Second Order Polynomial Regression Fit Exposure

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250 TABLE C3 Continued Exposure

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254 IT) crir^vcm'voc'3' Xi

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256 •^TrHiHrHtNmrH «^ >X) ^ vCrHr-l-HMnCN CM fNi^LD ^ in nrsi^r-HCNf^cN n mrO(y,'gin rnc^OI-ifS^^lnn oj >X)rHVDf^ ty\ r-> (JDrOrHrHCMr^CNJ m o^rHCN'^r CO en t^mr-tiniHincN en O C-H to -P •H (0 O U •H -H C tw ^ -H O 4-1 0) C O fe K H ffi O

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258 TABLE D7 Suimnary of Patient and Examination Characteristics During Personnel Exposure Study Monitored Characteristic

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259 Q) -P C cn •H OJ U E-i X S 4-1 P^ o 'O

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260 •H U iw U •H -l (0 a) -P 04 o Eh a en in CN iH iH r—l rQ M M nH M -P •H 0) oj vT) rCu Pm Oi A4

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262 TABLE El Bone and Red Marrow Assignment for Subfields of Adult Rando Phantom

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263 TABLE El Continued Subfield Structure Red Marrow Total Red Mass for Marrow Mass Structure in Subfield Cg) (g) Vertebra (T7) 12.1 Vertebra (T8) 13.9 Vertebra {T9) 14.8 Vertebra (TIO) 15.9 Left scapula 25.2 Left clavicle 8.1 Left humerus head 10-0 Left ribs: One-half rib 1 1.0 Rib 2 2.5 Rib 3 3.2 Rib 4 3.7 Rib 5 4.7 One-half rib 6 2.4 One-fourth rib 7 1.3 Right ribs : One-half rib 6 2.4 Threefourth rib 7 3.7 Rib 8 4.8 Rib 9 4.2 Rib 10 3.2 Rib 11 2.3 Rib 12 0.9 Vertebra (Til) 16.3 Vertebra {T12) 18.8 Vertebra (Ll) 20.8 Vertebra (L2) 21.8 Vertebra (L3) 23.8 Vertebra (L4) 24.1 Vertebra (L5) 23.6 Left ribs: One-half rib 6 2.4 Three-fourth rib 7 3.7 Rib 8 4.8 Rib 9 4.2 Rib 10 3.2 Rib 11 2.3 Rib 12 0.9 62.1 Red Marrow Fraction in Subfield 0.0594 21.5 0.0206 149.2 21.5 0.1427 0.0206

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264 TABLE El Continued

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255 TABLE E2 Bone and Red Marrow Assignment for Sub fields of Pediatric Phantoms Red Bone Marrov; Fraction^ Subfield Structure in Siib field 1 Skull 0.0694 2 Right hum.erus 0.0516 Right forearm (radius and ulna) 3 Right ribs 0.0772 Right scapula Right clavical 4a Sternum 0.0250 4b Cervical vertebra 0.0271 4b Thoracic vertebra (T1-T9) 0.0922 5 Left ribs 0.0772 Left scapula Left clavical 6 Left humerus 0.0516 Left forearm (radius and ulna) 7 Thoracic vertebra (T10-T12) 0.1352 Lumbar vertebra 8 Iliac bone 0.2875 Sacrum Ischium 9 Right femur 0.0530 10 Left fem.ur 0.0530 Total 1.0000 Red bone marrov/ values from Flashimoto and Yamaka (19 6 4) .

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266 O -r-i S O U u c o 0) o O -n a O Q) C O -P X O 0) u o C 5-1 (U o O 4J S U x; -n o o C M

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270 APPENDIX F The integral absorbed dose can be defined by the general formula: Z =C Ddm. VThere Z is the total integral dose, D the absorbed dose and m the total mass and dm a sm.all element of mass. In general terms the integral dose is equal to the incident energy reduced by the loss from the body due to scatter and transmission. The ICRU (19 59) further breaks down the elements of the integral dose as Zg , the ingegral absorbed dose within the confines of the beam, and Z„, the integral dose absorbed in the body not intercepted by the primary beam. Calculation m.ethods for obtaining Eg are quite straight forward. The evaluation of T.^ is more difficult due to the variation in size and shape of the body in which this quantity is to be determined. The ICRU suggests the methods described by Mayneord (19 40) and Meredith and Neary (19 44) as providing the most accurate method of estimating values for integral dose as of their 1959 publication date. Carlsson (19 6 3) re-examined the methods of Mayneord and carried out refinement calculations. In Mayneord 's original calculations, the integral dose values v;ere obtained from the central axis depth dose data integrated over the dimensions of the geometric beam and thus do not adequately account for losses due to lateral scatter. This error can be

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2 71 essentially removed if depth dose data for saturated scatter conditions are used. That is, if the depth dose data used are obtained for field sizes large enough that the central axis values no longer vary with increasing field size. If these central axis values are then integrated over the geometric dimensions of the beam, the loss due to lateral scatter out of this volume is accounted for. If this saturated scatter method is utilized, the assumption must be made that all lateral scatter is absorbed in the body or the method will overestim.ate the integral absorbed dose. F'or x-rays in the diagnostic x-ray region Carls son used the depth dose data of Trout and colleagues (19 60) . A second approach used by Carlsson was to calculate the incident energy fluence in air using the measured x-ray spectra of Hettinger and Starfelt (1958) and air attenuation coefficients. He shows that his calculated values are in close agreement with calorimetric determinations made by Laughlin and Genna (19 56). Once the energy fluence has been determined, the integral dose can be calculated by accounting for backscattered and transmitted energy. The results of these determinations are presented in Figure Fl . Carlsson calculated the integral dose utilizing the depth dose data of Trout and colleagues (1960) . Bomford and Burlin (1963) measured scatter from a 30 X 30 X 22 cm Mix-D phantom. They used circular beam sizes of 100 and 400 cm^ and tube potential settings in the

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272 diagnostic range of 100 and 140 kVp . No other statement regarding the geometry or beam quality is given, but it is not unreasonable to assume that they v/ere typical of those utilized in normal diagnostic practice. By integrating their graphical results, the scatter in specified lateral areas was obtained and is 3hov;n in Table Fl. From these data it can be seen that the greatest scatter is contained in the backscatter region and is accounted for in the depth dose values. The forward scatter which exits the phantom in the 90° to approximately 150° segment is seen to vary from approximately 3 to 11%. Pychlau and Bunde (1965) attempted to measure the integral dose in an adult wax phantom. Utilizing a Mai scintillation crystal they made multiple scatter measurements around aim diameter cylinder 1,4 m high surrounding the irradiated phantom. The results of these measurements were subtracted from the incident energy' flux to determine integral dose. The results of their measurements are also plotted in Figure Fl. Their values indicate a smaller value of absorbed energy per incident EAP . The Pychlau and Bunde values differ from the spectral calculated values of Carlsson by up to a factor of two. Since loss to lateral scatter cannot account for this magnitude of difference, some other factor must be involved. The effect of beam size and quality can be seen from the Pychlau and Bunde data. The integral dose per^ values are observed to increase with a decrease in beam. size.

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273 cy -P M M C m 3 QJ E CO O -H O H !-i w in o o rH r00 O 00 o 00 o en o o^ o en rH o rt! -P O C -P £ +-' Cn O CD 0) cn a. H (u e m S-J fC c 0) o XI X? +J -H >U ^ n3 (U u m tj I (U X O "-M -P •H C +J U 0) ;:; o 'O •H Oj-H o w o (^ c >i 0) -P cn g to O -' 0) {1)CN N g •a o CD -P P u u 0) U-J u o o o (Ti n3 "4-! X! — 4.) — (0 o o o O O -P o m in c; cn rH M •Mill O o o o O, ro cTi ro >-( 0) •P 4-> ^ (C J-i U 0) cn -P -P-ri tT3 M o tl3 cn ;5 O O O ^^ +J — 03 o o o O O -P o in in C cn rH .H •Hill O o o o Oi fo cn 00 0) cn +J +J Ti fC Sh u (ti cn s o u o cn (C3 y-J -P ^ (C3 o o o O O -P o in in C cn M rH •Hill O o o o CU 00 o^ rn ^ fO n o 0) cn cn o X o o cn (c3 Xi +J — to o +J O C cn •H I O O CM 00 I I o o cn 00 oooo oooo oooo oooo oooo oooo '^'*'^'* rHiHiHiH •^^'sT'^'^ to ^ •H a CD -P > 3 CD — F^ -p o a, oooo CD -P jU to Eh 'O

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274 15 Carlsson (1963) spectra calculations . 10 _. Pychlau and Bunde (19 65) phantom measurements. HALF VALUE LAYER (mm Al) Figure Fl. Integral Dose per EAP as a Function of X-ray Beam Quality Reported by Carlsson (1963) and Pychlau and Bunde (19 65) .

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275 This is due to the greater thickness of tissue surrounding the primary irradiated volume for any decrease in beam size. Carlsson (1965) states that for a 20 cm thick phantom with infinite lateral dimensions, the integral dose per EAP (grad/^) values calculated from the measured spectra are presumaiily better than + 20% accurate if the total filtration is equivalent to 4 mm of Al or greater. This determination was m.ade by calculating exposure and energy fluence from the measured spectra. At low energies, in the typical diagnostic region, the resolution of a Nal (Th) detector as used by Hettinger and Starfelt to measure the spectra is reduced to as much as 25% at 25 keV. The large variation of exposure fluence with energy at these lov/ energies is the major source of error. Additional variations must be considered when these conversion values for to g-rad are used on actual patients. Some of these factors include tissue inhomogeneities and positioning of the beam with respect to the body. If the beam does not completely intercept the body these conversion factors will overestimate the absorbed dose. The neglect of lateral scatter in the case of patients of finite dimensions must also be considered. From the v/ork of and Burlin, it was shown that this loss in a 30 x 30 x 22 cm Mix-D phantom, which might be typical of an adult, ranged from 3 to 11% for tube potentials in the range of 10 to 140 kVp . In the case of a child, an increased loss duo to scattered radiation would be antivjipated.

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276 Carlsson places the maximum error from neglecting lateral scatter in an adult at less than 8%. He goes on to state that the values he calculated for a 20 cm thick phantom vrould be 8 to 10% higher for a 15 cm thickness and would underestimate the integral dose from 2 to 9% for a 25 cm thickness. The determination of absorbed dose from external sources has also been carried out by use of Monte Carlo techniques. Sidwell, Burlin and ^Vheatley (19 69) and Jones and colleagues (1973) have published results for monoenergetic beams. The Sidwell calculations employed a 60 cm high eliptical cylinder whereas O'one ' s values were obtained utilizing the heterogeneous phantom developed by Snyder and colleagues (19 69) for estimation of absorbed fractions from internal emitters. More recently, Poston and Warner (19 74) have reported initial results using the Snyder phantom and techniques for continuous x-ray spectra. Using the data on diagnostic x-ray spectra reported by Epp and Weiss (1966) they calculated absorbed dose for a number of selected body sites, as well as values for the whole body. The simulation was established to represent a 36 x 44 cm (14 x 17 inch) beam incident to the posterior mid-trunk of the body. Data are presented for x-ray tube potentials over the range 45 to 10 5 kVp and added filtration values of 1 and 2 mm of Al. The Poston and Warner absorbed dose per incident R was converted to integral dose per EAP . The masses for the total body given by Snyder were used. These data are shown in

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277 Table F2 and plotted along with the Carlsson and Pychlau and Bunde values in Figure F2. In summary it can be seen that values of integral dose per incident EAP have been directly investigated or can be obtained from the p\±ilished data of a number of authors. Calculations have been performed utilizing depth dose data, x~ray spectra in conjunction v/ith attenuation values and Monte Carlo techniques. Experimental techniques have also been attempted. The results obtained from these methods show variations up to a factor of three for energies in the diagnostic x-ray range. The data reported by Carlsson are in general agreement v/ith values presented by Poston and Warner obtained by utilizing the Monte Carlo calculations. The Carlsson spectrally determined values were applied to the Group II patient data (see summary section of Chapter VII) . This set of values was chosen so that a comparison with the patient integral dose values reported by Kaude and Svahn (1975), which also used these conversion values, could be made. It must be kept in mind that these values are applicable to an x-ray beam incident on the trunk of the body of a normal size adult. For pediatric or large adult patients the values will over and underestimate the g-rad/R.cmrespectively. The values for the standard adult cannot be easily scaled to these alternate patients due to the number of variables associated with their determination.

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279 15 Carlsson (1963) spectra calculations. 10 -/ / grrrrZ — Pychlau and Bunde (19 6 5) phantom neasurements . 12 3 4 5 HALF VALUE LAYER (min Al) Figure F2. Integral Dose per EAP as a Function of Beam Quality Showing Additional Values Obtained from Monte Carlo Calculations of Poston and VJarner (1974) .

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REFERENCES Alderson, S.W., Lanzl, L.H., Rollins, M. and Spira, J., 1962, An instrumented phantom system for analog computations of treatment plans. Am. J. Roentg. 87:185-19 5. Alderson Research Laboratories, 1969, Alderson rando phantom system fcr radiotherapy. Technical Bulletin 42. Stamford, CT. Airth, G.R. , 1959, Routine incident radiation dosage measurements in barium meal examinations. Br. J. Radiol. 32: 61-64. Arnal, L. and Pychlau, H., 1961, Die strahlenben belastong des patienten bei rontgen-diagnostichen untersuchungen. Arztliche Forschung 16:247-255. Ardran, G.M. and Crooks, H.E., 1963, Routine dose recording in diagnostic radiology. Br. J. Radiol. 36:6 89-69 4. Ardran, G.M. and Crooks, H.E., 1965, The measurement of patient dose. Br. J. Radiol. 38:766-770. Ardran, G.M. and Fursden, P.S., 1973, Radiation exposure to personnel during cardiac catheterization. Radiology 106:517-518. Ardran, G.M., Hamill, J., Emrys-Roberts , E. and Oliver, R. , 19 70, Radiation dose to the patient in cardiac radiology, Br. J. Radiol. 43:391-394. Bang, I. and Kaude, J., 1967, Integral dose in hysterasalpingography with full size radiography and 70 mm fluorography. Radiology 7:275-279. Becker, K. , 1973, Solid state dosimetry. Cleveland, OH, CRC Press . Becker, K,, Cheka, J.S. and Oberhofer, M. , 19 69, Thermally stimulated exoelectron emission, thermoluminescence and impurities in LiF and BeO. Health Phys . 19:391-403. Bergstrom, K., Dahlin, H., Gustafsson, M. and Nylen, 0., 19 72, Eye lens doses in carotid angiography. Acta Radiol. 12:134-140. Bleichroder, F., 1912, Intraarterielle therapie . Berliner Klin. V-Jschr. 49:150 3-1504. 2 80

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281 Block, W.J., Crompacker, E.L., Dry, T.J. and Gage, R.P., 19 52, Prognosis of angina pectoris observations in 6,882 cases. J. Am. Med. Ass. 150:259-264. Bomford, C. K. and Burlin, T. E., 1963, The angular distribution of radiation scattered from a phantom exposed to 100-300 kVp x-rays. Br. J. Radiol. 36:436-439. Bureau of Radiological Health, 19 74, Gonad shielding in diagnostic radiology; FDA report 74-8028. Rockville, MD, U.S. Dept. of Health, Education and Welfare. Bushong, S.C., Pogonowska, M. J., Gerlock, A. J., Glaze, S.A. and Glaze, D.G., 19 73, Roentgen area product and exposure measurements during chest radiography and nephrotomography. Acta Radiol. 14:761-767. Cameron, J.R. , Suntharalingam, N.W. and Kenney , G.N. , 1968, Thermoluminescent dosimetry. Madison, WI , University of Wisconsin Press. Carlsson, C., 1963, Determination of integral absorbed dose from exposure measurements. Acta Radiol. 1:433-458. Carlsson, C, 1965, Integral absorbed doses in roentgen diagnostic procedures; part I: the dosimeter. Acta Radiol. 3:210-326. Carlsson, C. and Kaude, J., 1968, Integral dose in 70 mm fluorography of the gastroduodenal track. Acta Radiol. 7:84-88. Cope, C, 1959, Technique for transeptal catheterization of the left atrium; preliminary report. J. Thorac. Surg. 37:482-486. Cournard, A.F. and Ranges, H.A. , 1941, Catheterization of the right auricle in man. Proc. Soc. Exp. Biol, and Med. 46:462-466. Cox, F.M., Undated, New solid lithi\im fluoride thermoluminescent dosimeters. Solon, OH, Harshaw Chemical Company. Custer, R.P., 1949, An atlas of the blood and bone marrow. Philadelphia, PA, W.B. Saunders Company. DeVilleneuve, V.D., 1973, Biplane 70 mm intensifier fluorography in angiocardiographic examinations of congenital heart disease. Medicamundi 18:138-140.

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282 Dexter, L., Haynes , F.W., Burwell, C.S., Eppinger, E.G., Seibel, R.E. and Evans, J.M., 1947, Studies of congenital heart disease; parts I, II, and III. J. Clin. Invest. 26 : 547-576 . Dorph, S., Mygind, T., Northeved, A., O'Kholm, B., Petersen, K.O. and Orgaard, A., 19 70, A dose-reducing fluoroscopy system; dose measurements and clinical evaluation. Radiology 97:399-403. Edelmann, B.U., 1967, Ph.D. dissertation. East Germany, Technische Hechschule Dresden. Summary of results shown in: Becker, K. , 1973, Solid state dosimetry. Cleveland, OH, CRC Press. Eggermont, G. , Jacobs, R. , Janssens, A., Segaert, 0. and Thielens, G. , 19 71, Dose relationship, energy response and rate dependence of LiF-100, LiF-7 as CaSO^:Mn from 3 keV to 30 MeV. [In] Proc. 3rd Int. Conf. Luminescence Dosimetry, Riso, Denmark (October, 1971) pp 444, Ellis, P.E., 1961, The distribution of active bone marrow in the adult. Phys. Med. Biol. 5:255-258. Epp, E.R, and Weiss, K., 1966, Experimental study of the photon energy spectrum of primary diagnostic x-rays. Phys. Med. Biol. 11:225-238. Feddema, J. and Oosterkamp, W.J., 1953, Volume doses in diagnostic radiology. [In] McLaren, H.V7. (ed) . Modern Trends in Diagnostic Radiology. London, Butterworth and Co. pp 35-42. Fontana, R.S. and Edwards, J.E., 1962, Congenital cardiac disease; a review of 357 cases studied pathologically. Philadelphia, PA, W.B. Saunders. Frossman, VJ. , 1929, Die sondierung des rechten herzens . Klin. Wschr. 8:2085-2087. Gaugh, J. PI., David, R. and Stacey, A.J., 19 6 8, Radiation dose delivered to the skin, bone marrow and gonads of patients during cardiac catheterization and angiography. Br. J. Radiol. 41:508-518. Gignac, C.E., 19 74, A study of personnel exposures during cardiac catheterization; unpublished non-thesis master's paper. Gainesville, FL , Dept. of Nuclear Engineering, University of Florida.

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284 International Commission on Radiation Protection (ICRP) and the International Commission on Radiological Units and Measurements (ICRU) , 1961, Exposure of man to ionizing radiation arising from medical procedures with special reference to radiation induced diseases. Phy . Med. and Biol. 6:199-258. International Commission on Radiological Units and Measurements (ICRU), 1959. [In] National Bureau of Standards Handbook 78. 1961. Washington, DC, U.S. Government Printing Office. International Conmiission on Radiological Units and Measurements (ICRU), 1962, Radiobiological dosimetry. [In] National Bureau of Standards Handbook 88. 19 63. Washington, DC, U.S. Governm.ent Printing Office. International Commission on Radiological Units and Measurements (ICRU), 1969, Cameras for image intensifier f luorography; report 15. Washington, DC, ICRU Pioblications . Inter-Society Commission for Heart Disease Resources (ICHD) , 19 71, Optimal radiologic facilities for examination of the chest and cardiovascular system. Circulation 43: A135-A156. Jacobson, A., 1971, Radiation protection considerations of overhead fluoroscopic installations. Health Phys . 20: 55-58. Jacobson, A., Brooks, T. and Ackerman, M. , 1973, Evaluation of personnel dosimetry methods for diagnostic x-ray special procedures work. Health Phys. 25:66-80. Johns, H.E. and Cunningham, J.R., 1974. The physics of radiology (Third Edition, Revised Third Printing) . Springfield, IL, Charles C. Thomas. Jones, A. P.., 1964, Measurement of the dose absorbed in various organs as a function of the external gamma ray exposure. AECL-2240. Jones, D.E.A. and Raine, H.C., 19 49, Letter to the editor. Br. J. Radiol. 22:249-250. Jones, T.D., Auxier, J, A., Snyder, W.S. and V7arner, G.G., 1973, Dose to standard reference man from external sources of monoenergetic photons. Health Phys. 24:241255. Judkins, M.P., 1967, Selective coronary arteriography, a percutaneous transfemoral technique. Radiology 89:815-824.

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285 Kannel, W.B. and Feinleik, M. , 1972, Natural history of angina pectoris in the Framingham study. Am. J. Cardiol. 29:154-163. Katta, K.S., 1975, Determination and analysis of patient radiation exposure due to cardiovascular special x-ray procedures; master's degree thesis. Gainesville, FL, University of Florida. Kaude, J.V., 196'', Clinical studies on image intensifier fluorography and cine f luorography . Acta Univ. Lund., Sect, il, 18:1-16. Kaude, J.V., Lorenz, E. and Reed, J.M., 1969, Gonad doses to children in voiding urethrocystography performed with 70 mm image intensifier fluorography. Radiology 92: 771-774. Kaude, J.V. and Reed, J.M., 1969, Voiding urethrocystography by means of 70 rrim image intensifier fluorography. Radiology 92:768-770. Kaude, J. and Svahn, G., 1974, Absorbed gonad and integral doses to the patient and personnel from angiographic procedures. Acta Radiol. 15:454-464. Klement, A.W., Miller, C.R., Minx, R.P. and Shleien, B., 19 72, Estimates of ionizing radiation doses in the United States 1960-2000; EPA report ORP/CSD 72-1. VJashington, DC, U.S. Government Printing Office. Lanzl, L.H., 1973, The rando phantom and its miedical applications. Stamford, CT , Alderson Research Laboratories. Larsson, L.E., 195 8, Radiation to the gonads of patients in Swedish roentgen diagnostics. Acta Radiol. Suppl. 157. Larsson, L.E., 1956, Radiation doses to patients and personnel in modern roentgen diagnostic work. Acta Radiol. 46: 680-689 . Laughlin, J.S, and Genna, S., 19 56, Calorimetric methods. [In] Hine, G.J. and Brovmell, G.L. Radiation dosimetry. New York, Academic Press. pp 411-452. Liuzzi, A., Blatz, H. and Eisenbud, M. , 1964, A method for estimating the average bone-marrov; dose from some fluoroscopic examinations. Radiolog-y 82:99-105. MacMahon, B.M., Thomas and Record, R.C., 1953, The incidence and life expectation of children with congenital heart disease. Br. Heart J. 15:121-129.

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2 86 Maddison, F.E, and Handel, S.F., 1974, A rapid-sequence 105 ram photospot device. Applied Radiology March/April. Malsky, S.J., Haft, J., Haft, D., Gould, L. , Blatt, C, Simon, D.F. and Roswit, B., 1972, Radiation exposure to staff cardiologist vs. senior resident cardiologist and patients during cardiac catheterization. Rad. Data Rep. 13:387-391. Malsky, S.J., Roswit, B., Reid, C.B. and Haft, J., 1971, Radiation exposure to personnel during cardiac catheterization. Radiology 100:671-674. Mayneord, V;.V., 1940, Energy absorption. Br. J. Radiol, 13: 235-247. McGinn, S. and VJhite, P.D., 19 36, Progress in recognition of congenital heart disease. Nev; Engl. J. Med. 214:76 3768. Mechanik, N., 1926, Studies of the weight of bone marrov/ in man. Zeit for die Gest. Anat. 79:58-99. Meredith, W.J. and Neary, G.J., 1944, The production of isodose curves and the calculation of energy absorbed from standard depth dose data. Br. J. Radiol. 17:7582. Morgan, R.H., 1961, The measurement of radiant energy levels in diagnostic roentgenology. Radiology 76:867-876. Morgan, R.H. and Gehret, E.F., 19 71, Gonad exposure in medical radiography; BRH/DMRE Contract Report PH 86-6 8-63. Rockville, MD , Bureau of Radiological Health, U.S. Dept. of Health, Education and Welfare. Morgan, T. and Fewell, T.R., 1973, Comparison of correction factors and spectra for x-ray beams having common half value layers; unpublished internal report. Rockville, MD, Bureau of Radiological Health, U.S. Dept. of Health, Education and Welfare. National Council on Radiation Protection and Measurements (NCRP) , 19 68, Medical x-ray and gamma-ray protection for energies up to 10 MeV — equipment design and use; report 33. Washington, DC, NCRP publications. National Council on Radiation Protection and Measurements (NCRP), 1970, Medical x-ray and gamma-ray protection for energies up to 10 MeV--structural shielding design and evaluation; report 34, Washington, DC, NCRP publications.

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287 National Council on Radiation Protection (NCRP) , 19 71, Basic radiation protection criteria; report 3S , Vvashington, DC, NCRP publications. Piney, A., 1922, The anatomy of the bone marrow. Br. Med. J. '2:792-795. Poston, J.W. and Warner, G.G., 1974, Absorbed dose to selected internal organs from typical diagnostic x-ray exposures. [In] Health Physics Division Annual Progress Report for Period Ending July 31, 1974; ORNL report 4979, UC-41. TN, Oak Ridge National Laboratory. Pychlau, P. and Bunde, E., 19 65, The absorption of x-rays in a body equivalent phantom. Br. J. Radiol. 38:875-877. Reinsma, K. , 1960, The inherent filtration of x-ray tiabes. Radiology 74:9 71-9 72. Reinsma, K., 1962, Dosimeters for x-ray diagnosis. Eindlioven, Philips Technical Library. Richards, D.V7., Bland, E.F. and White, P.O., 1956, Complete 25 year followup study of 456 patients with angina pectoris. J. Chron. Dis . 4:423-433. Richards, M.R. , Merritt, K.K. , Samuels, M.H. and Langmann, A.G. , 1955, Congenital malformations of the cardiac system in a series of 6,053 infants. Pediatrics 15:1232. Ricketts, H.J. and Abrams, H.L., 19 62, Percutaneous selective coronary cine arteriography. J. Am. Med. Ass. 181:620624. Ross, J., 1959, Transseptal left heart catheterization: a new method of left atrial puncture. Ann. Surg. 149: 395-401. Rowley, K.A. , 1974, Patient exposure in cardiac catheterization and cinefluorography using the eclair 16 mm camera at speeds up to 200 frames per second. Br. J. Radiol. 47:169-178. Seidlitz, L. and Margalis , A.R., 1974, Doses to the vertebral marrow during common x-ray examinations in clinical situations. Invest. Radiol. 6:419-424. Seldinger, S.I., 1953, Catheter replacement of the needle in percutaneous arteriorography ; a new technique. Acta Radiol. 39:369-376.

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28! Shleien, E., 1973, A review of determinations of radiation dose to the active bone marrow for diagnostic x-ray examinations; FDA report 74-800 7. Rockville, MD. Bureau of Radiological Health, U.S. Dept. of Health, Education and Welfare. Sidwell,J.M., Burlin, T.E. and Wheatley, B.M.,1969, Calculations of the absorbed dose in a phantom from photon fluence and some applications to radiological protection. Br. J. Radiol. 42:522-529. Siedband, M.P., 1973, Limitations of exposure reduction during fluoroscopy by image storage. Proc. Soc. PhotoOpt. Eng. 43:151-154. Snyder, W.S., Ford, M.R. , Warner, G.G. and Fischer, K.L., 1969, Estim^ates of absorbed fractions from monoenergetic photon sources uniformly distributed in various organs of a heterogeneous phantom; MIRD phamphlet 5. J. Nucl. Med., Suppl. 3, 10:5--52. Sones, P.M., Shirey, E.K., Proudfit, W.L. and Westcott, R.N., 19 49, Cine-coronary arteriography. [In] Abstracts of the 32nd Scientific Session of the American Heart Association. Circulation 22:773-774. Sourkes, T.L., 1966, Nobel prize winners in medicine and physiology; 1901-1965, London, Abelard-Schuman. Spiers, F.W., 1969. Transition-zone dosimetry; chapter 32. [In] Radiation Dosimetry, Vol. Ill ed. by: Attix F.H., Roesch, W.C. and Tochilin, E., New York, Academ.ic Press. Stacey, A. J. , Davis, R. , and Kerr, I.H., 1974, Personnel protection during cardiac catheterization with a comparison of the hazards of under couch and over couch x-ray tube monitoring. Br. J. Radiol. 47:16-23. Stanford, R.W. and Vance, J., 1955, The quantity of radiation received by the reproductive organs of patients during routine diagnostic x-ray examinations. Br. J. Radiol. 28:266-273. Trout, E.D., Kelley, J. P. and Lucas, A.C., 1960, Influence of cable length on dose rate and half value layer in diagnostic x-ray procedures. Radiology 14:255-264. United Nations, 19 72, Report of the united nations scientific committee on the effects of atomic radiation; part I: levels. New York, United Nations publications.

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2 89 Van de Wetering, H., 1971, Automation in x-ray generation. Medicamundi 16 : 9 8-10 = White, P.D., 1955, The natural history of congenital cardiovascular defects. [In] Congenital Heart Disease: Report of the Fourteenth M. and R. Pediatric Research Conference. Columbus, OH, M. and R. Laboratories. White, P.D., Bland, E.F. andMiskall, E.W., 1943, Prognosis of angina pectoris: long-time followup of 49 7 cases including notes on 75 additional cases of angina pectoris decubitus. J. Am. Med. Ass. 123:801-804. I'Jholey, M.H., 1974, Clinical dosim.etry during the angiographic examination; comments on coronary arteriography. Circulation 50:627-631. Wold, G.J., Scheele, R.V. andAgarwal, S.K., 1971, Evaluation of physician exposure during cardiac catheterization. Radiology 99:188-190. Zimmerman, H.A., Scott, R.W. and Becker, N.D., 1950, Catheterization of the left side of the heart. Circulation 1:357-359.

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BIOGRAPHICAL SKETCH William Stuart Properzio v/as born February 21, 19 40, in Keene, New Hampshire. He is married to the former Sharon Carlisle and they have one daughter, Angela Marie. He attended the primary and secondary schools of Winchendon, Massachusetts graduating from Murdock High School in 1958. In 19 62 he received a bachelor of science degree in electrical engineering from Worcester Polytechnic Institute. Following graduation he was briefly employed as a computer systems design engineer v/ith the International Business Machines Corporation. In 19 62 he accepted an appointment in the Commission Corps of the United States Public Health Service. At the present time he is still on active duty and holds the rank of engineer senior grade (equivalent to a Naval Commander, 0-5). Assignments in the Public Health Service have all been in areas related to radiological health. From. 1962 to 1965 he was at the Robert A. Tafc Engineering Center, Cincinnati, Ohio. He v/as next assigned to the X-ray Science and Engineering Laboratory program at Oregon State University from 19 65 to 19 68. While at Oregon State he held the rank of instructor and v/as involved with both teaching and research. During the academic year 1966/1967 he was a full 290

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291 time graduate student and received a master of science degree in radiological physics. In 19 6 8 he was transferred to the Bureau of Radiological Health's headquarters in Rockville, Maryland, where ha worked in the X-ray Exposure Control Laboratory' and was in charge of laboratory operation from. 19 69 to 19 72. Graduate study at the University of Florida v/as initiated in September of 19 72.

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for tiie degree of Doctor of Philosophy. Charles E. Roessler, Chairman Associate Professor of Environmental Engineering Sciences I certify that I have read this study and that in my opinion it confoi-m.s to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. William Emmett-^Bolch' Associate Professor of Environmental Engineering Sciences I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. <^arry P .TE-iliott of Radicylogy Professor I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Docror of Philosophy. 0]a[[^, \ (Ob^ciMT). Walter Mauderli, of Radiology Professor

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This thesis v/as submitted to the Graduate Faculty of the College of Engineering and to the Graduate Council, and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy. June, 19 75 Dean, Graduate Scncol