Bush__The_Essential_Physics_for_Medical_Imaging - Biomedical ...

isks. The International Commission on Radiological Protection (ICRP) estimates therisk of fatal cancer for exposures to adults of working age to be 4 X 10- 2 deaths per Sv(4 X 10-4 per rem). This translates to 1 cancer death per 2,500 people receiving aneffective dose of 10 mSv (1 rem). Because of the linear, no-threshold assumption usedin risk estimates, risk is presumed to be proportional to the effective dose. For example,there would be a 1 in 25,000 chance that a fatal cancer would result from an effectivedose of 1 mSv (0.1 rem), or a 1 in 500 chance of a fatal cancer from an effectivedose of 50 mSv (5 rem). The ICRP estimates the risk to be two or three times higherfor infants and children, and substantially lower for adults older than 50 years of age(see later discussion of radiation-induced cancer risk, Chapter 25.6).In addition to understanding the risk per unit effective dose, a working knowledgeof the typical dose levels or effective doses for various common radiologic proceduresis useful. Table 24-3 is a compilation of typical organ doses and effective doses for avariety of diagnostic imaging procedures. Table 24-4 contains results from a study ofpatient radiation doses resulting from interventional radiologic procedures.TABLE 24·4. RANGE OF FLUOROSCOPY SCREENING TIME, FLUOROSCOPY ANDRADIOGRAPHY DOSE·AREA PRODUCT VALUES, AND MEAN EFFECTIVE DOSEFOR SELECTED INTERVENTIONAL PROCEDURESDose-area product (Gy-cm 2 )" MeanFluoroscopyeffectiveInterventional screening doseprocedures time (min) Fluoroscopy Radiography (mSv)"DiagnosticAV fistula angiography 1.4-3.8 0.3-36.3 0.8-26.2 0.2Upper extremity angiography 3.6-8.1 2.5-29.8 3.9-60.2 0.3Lower extremity angiography 1.8-21.7 1.0-82.2 0.2-1.42 0.8Nephrostography 0.9-24.7 0.1-72.9 0.0-14.2 2.4Carotid angiography 2.6-21.0 2.6-79.8 4.7-63.7 4.9Transjugular hepatic biopsy 2.8-18.7 5.5-95.3 0.0-25.4 5.5Renal angiography 2.9-7.6 4.7-31.6 12.7-40.2 6.4Cerebral angiography 2.9-36.0 7.7-121 10.8-76.6 7.4Femoral angiography 1.8-17.2 1.0-44.6 0.2-91.8 7.5Thoracic angiography 0.6-114 2.2-167 9.2-115 11.9PTC 2.9-44.0 12.0-1.92 0.0-11.3 12.8CT arterial portography 2.3-25.8 17.1-231 0.0-56.5 12.9Abdominal angiography 1.8-27.1 13.0-102 5.4-227 18.9Hepatic angiography 3.6-41.8 22.8-168 16.2-149 21.7TherapeuticAV fistula angioplasty 4.8-57.9 0.2-96.3 0.9-45.1 0.3Biliary stent insertion/removal 0.6-26.3 3.1-137 0.0-18.7 6.9Nephrostomy 1.3-20.8 0.6-160 0.0-44.7 6.9Cerebral embolization 15.2-55.8 28.3-61.9 36.3-162 10.5Renal angioplasty 11.4-27.2 5.4-190 2.6-77.7 13.6Thoracic therapeutic procedures 4.2-35.0 4.5-182 10.9-168 16.3Other abdominal therapeutic 6.6-58.8 16.9-413 1.1-229 26.9procedures (excluding hepaticand renal)TIPS 21.7-100 212-897 61.4-234 83.9"1 Gy = 100 rads; 1 mSv = 100 mrem.Note: AV, arteriovenous; CT, computed tomography; PTC, percutaneous transhepatic cholangiography;TIPS, transjugular intrahepatic portosystemic stunt.Adapted from McParland BJ: A study of patient radiation doses in interventional radiological procedures.Bf J Radio/1998;71:175-185.