This study provides a retrospective assessment of doses to 13 organs for the most common radiographic examinations conducted between the 1930s and 2010, taking into account typical technical parameters used for radiography during those years. This study is intended to be a resource on changes in medical diagnostic radiation exposure over time with a specific purpose of supporting retrospective epidemiological studies of radiation health risks. The authors derived organ doses to the brain, esophagus, thyroid, red bone marrow, lungs, breast, heart, stomach, liver, colon, urinary bladder, ovaries, and testes based on 14 common radiographic procedures and compared, when possible, with doses reported in the literature. These dose estimates were based on radiographic exposure parameters described in textbooks widely used by radiologic technologists in training from 1939 to 2010. The derived estimated doses presented here are believed to be representative of typical organs for an average-size adult who might be considered to be similar to the reference person. There were large variations in organ doses noted among the different types of radiographic examinations. Doses were highest in organs within the area imaged and next highest in organs in close proximity to the area imaged. Estimated organ doses have declined substantially [overall 22-fold (±38)] over time as a consequence of changes in technology, imaging protocols and protective measures. For some examinations, only slight differences were observed in doses for the decades of the 1960s, 1970s, and 1980s due to minor changes in technical parameters. Substantial dose reductions were observed in the 1990s and 2000s.

This study summarizes and compares estimates of radiation absorbed dose to the thyroid gland for typical patients who underwent diagnostic radiology examinations in the years from 1930 to 2010. We estimated the thyroid dose for common examinations, including radiography, mammography, dental radiography, fluoroscopy, nuclear medicine, and computed tomography (CT). For the most part, we observed a clear downward trend in thyroid dose over time for each procedure. Historically, the highest thyroid doses came from the nuclear medicine thyroid scans in the 1960s (630 mGy), full-mouth series dental radiography (390 mGy) in the early years of the use of x-rays in dentistry (1930s), and the barium swallow (esophagram) fluoroscopic exam also in the 1930s (140 mGy). Thyroid uptake nuclear medicine examinations and pancreatic scans also gave relatively high doses to the thyroid (64 mGy and 21 mGy, respectively, in the 1960s). In the 21st century, the highest thyroid doses still result from nuclear medicine thyroid scans (130 mGy), but high thyroid doses are also associated with chest/abdomen/pelvis CT scans (18 and 19 mGy for male and females, respectively). Thyroid doses from CT scans did not exhibit the same downward trend as observed for other examinations. The largest thyroid doses from conventional radiography came from cervical spine and skull examinations. Thyroid doses from mammography (which began in the 1960s) were generally a fraction of a mGy. The highest average doses to the thyroid from mammography were about 0.42 mGy, with modestly larger doses associated with imaging of breasts with large compressed thicknesses. Thyroid doses from dental radiographic procedures have decreased markedly throughout the decades, from an average of 390 mGy for a full-mouth series in the 1930s to an average of 0.31 mGy today. Upper GI series fluoroscopy examinations resulted in up to two orders of magnitude lower thyroid doses than the barium swallow. There are considerable uncertainties associated with the presented doses, particularly for characterizing exposures of individual identified patients. Nonetheless, the tabulations provide the only comprehensive report on the estimation of typical radiation doses to the thyroid gland from medical diagnostic procedures over eight decades (1930–2010). These data can serve as a resource for epidemiologic studies that evaluate the late health effects of radiation exposure associated with diagnostic radiologic examinations.

ObjectiveTo assess whether personal medical diagnostic procedures over life, but particularly those associated with exposure in adulthood, were associated with increased thyroid cancer risk.DesignParticipants from the US Radiologic Technologists Study, a large, prospective cohort, were followed from the date of first mailed questionnaire survey completed during 1983–1989 to the earliest date of self-reported diagnosis of thyroid cancer or of any other cancer than non-melanoma skin cancer (NMSC) in any of three subsequent questionnaires up to the last in 2012–2014.SettingUS nationwide, occupational cohort.ParticipantsUS radiologic technologists with exclusion of: those who reported a previous cancer apart from NMSC on the first questionnaire; those who reported a cancer with an unknown date of diagnosis on any of the questionnaires; and those who did not respond to both the first questionnaire and at least one subsequent questionnaire.Primary outcome measureWe used Cox proportional hazards models with age as timescale to compute HRs and 95% CI for thyroid cancer in relation to cumulative 5-year lagged diagnostic thyroid dose.ResultsThere were 414 self-reported thyroid cancers (n=275 papillary) in a cohort of 76 415 persons. Cumulative thyroid dose was non-significantly positively associated with total (excess relative risk/Gy=2.29 (95% CI −0.91 to 7.01, p=0.19)) and papillary thyroid cancer (excess relative risk/Gy=4.15 (95% CI −0.39, 11.27, p=0.08)) risk. These associations were not modified by age at, or time since, exposure and were independent of occupational exposure.ConclusionOur study provides weak evidence that thyroid dose from diagnostic radiation procedures over the whole of life, in particular associated with exposure in adulthood, influences adult thyroid cancer risk.