Data have been collected and physical and statistical models have been constructed to estimate unknown occupational radiation doses among 90,000 members of the U.S. Radiologic Technologists cohort who responded to a baseline questionnaire during the mid-1980s. Since the availability of radiation dose data differed by calendar period, different models were developed and applied for years worked before 1960, 1960- 1976 and 1977-1984. The dose estimation used available film-badge measurements (approximately 350,000) for individual cohort members, information provided by the technologists on their work history and protection practices, and measurement and other data derived from the literature. The dosimetry model estimates annual and cumulative occupational badge doses (personal dose equivalent) for each technologist for each year worked from 1916 through 1984 as well as absorbed doses to organs and tissues including bone marrow, female breast, thyroid, ovary, testes, lung and skin. Assumptions have been made about critical variables including average energy of X rays, use of protective aprons, position of film badges, and minimum detectable doses. Uncertainty of badge and organ doses was characterized for each year of each technologist's working career. Monte Carlo methods were used to generate estimates of cumulative organ doses for preliminary cancer risk analyses. The models and predictions presented here, while continuing to be modified and improved, represent one of the most comprehensive dose reconstructions undertaken to date for a large cohort of medical radiation workers.

A health survey of more than 143,000 radiologic technologists is described. The population was identified from the 1982 computerized files of the American Registry of Radiologic Technologists, which was established in 1926. Inactive members were traced to obtain current addresses or death notifications. More than 6000 technologists were reported to have died. For all registrants who were alive when located, a detailed 16‐page questionnaire was sent, covering occupational histories, medical conditions, and other personal and lifestyle characteristics. Nonrespondents were contacted by telephone to complete an abbreviated questionnaire. More than 104,000 responses were obtained. The overall response rate was 79%. Most technologists were female (76%), white (93%), and employed for an average of 12 years; 37% attended college, and approximately 50% never smoked cigarettes. Radiation exposure information was sought from employer records and commercial dosimetry companies. Technologists employed for the longest times had the highest estimated cumulative exposures, with approximately 9% with exposures greater than 5 cGy. There was a high correlation between cumulative occupational exposure and personal exposure to medical radiographs, related, in part, to the association of both factors with attained age. It is interesting that 10% of all technologists allowed others to practice taking radiographs on them during their training. Nearly 4% of the respondents reported having some type of cancer, mainly of the skin (1517), breast (665), and cervix (726). Prospective surveys will monitor cancer mortality rates through use of the National Death Index and cancer incidence through periodic mailings of questionnaires. This is the only occupational study of radiation employees who are primarily women and should provide new information on the possible risks associated with relatively low levels of exposure.586‐598.

In this article, we describe recent methodological enhancements and findings from the dose reconstruction component of a study of health risks among U.S. radiologic technologists. An earlier version of the dosimetry published in 2006 used physical and statistical models, literature-reported exposure measurements for the years before 1960, and archival personnel monitoring badge data from cohort members through 1984. The data and models previously described were used to estimate annual occupational radiation doses for 90,000 radiological technologists, incorporating information about each individual's employment practices based on a baseline survey conducted in the mid-1980s. The dosimetry methods presented here, while using many of the same methods as before, now estimate 2.23 million annual badge doses (personal dose equivalent) for the years 1916–1997 for 110,374 technologists, but with numerous methodological improvements. Every technologist's annual dose is estimated as a probability density function to reflect uncertainty about the true dose. Multiple realizations of the entire cohort distribution were derived to account for shared uncertainties and possible biases in the input data and assumptions used. Major improvements in the dosimetry methods from the earlier version include: A substantial increase in the number of cohort member annual badge dose measurements; Additional information on individual apron usage obtained from surveys conducted in the mid-1990s and mid-2000s; Refined modeling to develop lognormal annual badge dose probability density functions using censored data regression models; Refinements of cohort-based annual badge probability density functions to reflect individual work patterns and practices reported on questionnaires and to more accurately assess minimum detection limits; and Extensive refinements in organ dose conversion coefficients to account for uncertainties in radiographic machine settings for the radiographic techniques employed. For organ dose estimation, we rely on well-researched assumptions about critical exposure-related variables and their changes over the decades, including the peak kilovoltage and filtration typically used in conducting radiographic examinations, and the usual body location for wearing radiation monitoring badges, the latter based on both literature and national recommendations. We have derived organ dose conversion coefficients based on air-kerma weighting of photon fluences from published X-ray spectra and derived energy-dependent transmission factors for protective lead aprons of different thicknesses. Findings are presented on estimated organ doses for 12 organs and tissues: red bone marrow, female breast, thyroid, brain, lung, heart, colon, ovary, testes, skin of trunk, skin of head and neck and arms, and lens of the eye.

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