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Discovering the causes of cancer and the means of prevention

Medical Radiation Worker Studies

Different sources of data as well as relevant dosimetric models are being used to reconstruct occupational radiation doses to medical workers during decades ranging from the 1950s to the present. Some of the important data available include extensive historical information collected from the literature, more than 1,000,000 film-badge measurements from private laboratories, employers, the military and commercial dosimetric service providers, and detailed work history data (job history; types of procedures performed, protective measures undertaken or clothing or other accessories worn; behavioral practices). Annual and cumulative occupational badge doses for medical radiation technologists have been for each year worked has been reconstructed and used to estimate organ-specific radiation absorbed doses. These estimates include consideration of important variables such as the use protective clothing, exposure geometry and x-ray energy. Estimates of doses to the thyroid, female breast, ovary, lens of eye, lung, colon, testes, heart, skin (front side only), and red bone marrow have been completed. The uncertainty of both badge and organ doses for each year of each technologist’s working career is being characterized using Monte Carlo simulation methods. Reconstruction of occupational radiation doses has been a major focus of the U.S. Radiologic Technologists cohort study.

Given the uncertainties and assumptions required in this dose reconstruction effort, methods are needed to examine the validity of estimated doses. Measurement of stable chromosome aberrations in peripheral blood lymphocytes using fluorescence in situ hybridization (FISH) has been an accepted method to estimate radiation exposure levels that have occurred well into the past. Among 149 USRT cohort members that began working before 1950, we have measured stable chromosome aberration frequencies and related them to the estimated dose. Recently, a significant, positive relationship between aberration frequency and estimated dose was confirmed, providing corroboration of the estimated doses. Further analyses of these data are underway to determine any modifications to the dose reconstruction that might improve the estimated doses.

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