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performed with manual contrast injections. Each of the three surgeons participating in the procedures wore three radiation dosimeters (Landauer, Inc, Glenwood, Ill); they were worn (1) on the waist under the lead apron, (2) on the waist outside the lead apron, and (3) on the collar outside the thyroid shield. A ring dosimeter was worn on the ring finger of the left hand by each surgeon. Additional badges were placed on the operating table at the patients' right shoulder (20-30 cm from source), at the foot of the operating table (120-140 cm from source), and in the corner of the operating room (> 3 m from source). These badges were used to estimate the exposure to the patient, scrub nurse, and circulating nurse. The minimum detectable radiation dose for these badges is 10 mrem, which is equal to 0.1 mSv. In cases where the badges read “minimal” (ie < 10 mrem), a value of 5 mrem or 0.05 mSv was arbitrarily assigned. Patient entrance doses were calculated with the fluoroscopic energies and positions recorded during each case. Badge readings were performed independently (Landauer, Inc) on a monthly basis and forwarded to the Department of Nuclear Medicine. Total effective doses (TEDs) were calculated according to the formula TED = (y dose [under lead] × 1.5) + (y dose [collar] × 0.04). They were then compared with standards established by the International Commission on Radiological Protection (ICRP).2 Deep dose readings were used rather than shallow dose readings because these are thought to more closely approximate risk. Results Total fluoroscopy time for the 47 EAIA repairs was 30.9 hours (1852 minutes; mean, 39.4 minutes per case). The time spent using high-level fluoroscopy varied between 5% and 37%, although in one case it was as high as 60%. The milliampere ranged from 2.1 to 4.7 and the kilovolt from 65 to 105. Yearly TEDs for the surgeons (under lead) were 1.52 mSv, 1.64 mSv, and 0.92 mSv (Table).All were below the 20 mSv/y ICRP occupational exposure limit, and one was below the 1 mSv/y civilian limit. Outside lead doses for all surgeons exceeded civilian limits and in two cases approximated the recommended occupational limits. Lead aprons attenuated 85% to 91% of the dose. Percentages are ICRP occupational dose limit. Ring doses were 18.69 mSv/y, 16.00 mSv/y, and 5.44 mSv/y (Table). Calculated eye doses were 7.77 mSv/y, 5.67 mSv/y, and 2.04 mSv/y. These were within ICRP occupational exposure limits. Patient entrance doses averaged 360 mSv per case (range, 120-860 mSv). Yearly doses measured at the patient's right shoulder were 40 mSv. The yearly dose measured at the foot of the operating table was 2.59 mSv. The ambient (> 3 m from the source) operating room dose was 1.06 mSv/y. Discussion Radiation effects The biologic effects of radiation can be divided into two types, deterministic and stochastic.2 Deterministic effects are observed only when many cells in an organ or tissue are killed by virtue of a dose above a given threshold. Stochastic effects are due to radiation-induced injury to the DNA of a single cell and have no threshold. However, the probability of an effect is small. Stochastic effects may be either somatic or hereditary. It is these stochastic effects that are of concern because there is no low threshold. There are many sources of background radiation within the environment, both naturally occurring and man-made. Radon gas constitutes the single most important source of naturally occurring external background radiation, followed closely by solar, cosmic, and galactic radiation. Natural atmospheric radiation, radionuclides, terrestrial nuclides, nuclear reactors, and the testing of nuclear weapons all contribute to background radiation. Radiation exposure is cumulative, and effects are permanent. The total exposure for an individual performing fluoroscopic procedures is the sum of the individual's exposure during these procedures plus background exposure and any incidental medical exposure (eg, diagnostic chest radiograph) that are incurred. In the United States, the average person receives approximately 3.5 mSv per year in background exposure. This dose increases with altitude and other local factors, such as radionuclides, in the soil. There are several
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