Thyroid Radiation Dose to Patients from Diagnostic Radiology Procedures over Eight Decades

Abstract

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.

Assessment of thyroid cancer risk associated with radiation dose from personal diagnostic examinations in a cohort study of US radiologic technologists, followed 1983–2014

“…Shown in online supplementary file appendix A table A1 are the estimated absorbed doses to the thyroid gland by diagnostic procedure and calendar period, derived from a comprehensive literature review of 14 common types of diagnostic radiological examination. 10 13 For diagnostic x-rays of the collar bone and shoulder, Chang et al 10 estimated radiological parameters for each procedure (number and type of projections, kVp, field size, mAs) from a radiological positioning textbook series 14–21 and then calculated doses using the Monte Carlo PCXMC code. 22 Doses for mammography and thyroid scan were assumed to be 0 before 1960, as it was thought unlikely that these types of procedure would have been performed during those early time periods.…”

“…Dose estimates were derived using a novel regression method, based on questionnaire-derived number and type of radiological procedures, combined with estimated time period-specific doses from comprehensive literature review and calculated based on machine parameters reported in the literature for radiological examinations during 1930–2009. 10 We assessed variations of risk by time since exposure and exposure age, as well as by thyroid cancer histological type. In particular, we assessed contributions to thyroid cancer risk associated with exposure in adulthood.…”

Assessment of PCXMC for patients with different body size in chest and abdominal x ray examinations: a Monte Carlo simulation study

“…The software has been used in several epidemiological and risk projection studies of cancer risk in patients undergoing x ray examinations (Zenone et al , 2012; Baysson et al , 2015; Harbron et al , 2015; Baysson et al , 2013; Harbron et al , 2016; Ladia et al , 2015). Researchers at the National Cancer Institute have also used the PCXMC to estimate medical radiation doses from over eight decades of diagnostic radiation procedures(Melo et al , 2016; Chang et al , 2017). However, the built-in computational phantoms in the PCXMC are a set of pediatric and adult stylized phantoms developed at Oak Ridge National Laboratory (ORNL) in the 1980s (Cristy and Eckerman, 1987).…”

Dental X-Rays and the Risk of Thyroid Cancer and Meningioma: A Systematic Review and Meta-Analysis of Current Epidemiological Evidence

“…(64) It is anticipated that with newer generation digital imaging systems, which utilize very short exposure times, patient doses will gradually also decrease in panoramic radiography. (64) In a recent study, Chang et al (65) summarised and compared estimates of absorbed radiation dose by the thyroid in patients who underwent diagnostic radiographic examinations during the years 1930-2010. It was estimated that the thyroid doses from dental radiography 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 at present.…”