Reconstruction of Radiation Dose Received by Diagnostic Radiologic Technologists in Korea

Estimation of the historical radiation dose of Korean radiation workers, 1961-1983

Accurate dosimetry plays a key role in evaluating the radiation-induced health risks of radiation workers. The National Dose Registry in Korea contains the dose records of radiation workers in nuclear-related occupations since 1984. Thus, radiation doses for workers before 1984 are often sparse or missing. This study aimed to estimate the historical radiation dose before 1984 for radiation workers in Korea based on dose reconstruction models. The dose reconstruction models were derived from the nationwide self-administered questionnaire survey and the personal badge doses for workers in the cohort of the Korean Radiation Worker Study. The mean estimated annual doses between 1984 and 2016 from the dose reconstruction model were 4.67-0.6 mSv, which closely matched the reported doses of 4.51-0.43 mSv. The mean estimated annual doses between 1961 and 1983 based on the exposure scenarios developed by factors associated with radiation doses ranged from 11.08 to 4.82 mSv. The mean estimated annual doses of individuals in the cohort from 1961 to 1983 ranged from 11.15 to 4.88 mSv. Although caution needs to be exercised in the interpretation of these estimations due to uncertainty owed to the nature of extrapolation beyond the range of observed data, this study offers a sense of the radiation doses for workers during Korea's early period of radiation-related activities, which can be a useful piece of information for radiation-induced health risk assessments.

Trends in Occupational Radiation Doses for U.S. Radiologic Technologists Performing General Radiologic and Nuclear Medicine Procedures, 1980-2015

Background Occupational doses to most medical radiation workers have declined substantially since the 1950s because of improvements in radiation protection practices. However, different patterns may have emerged for radiologic technologists working with nuclear medicine because of the higher per-procedure doses and increasing workloads. Purpose To summarize annual occupational doses during a 36-year period for a large cohort of U.S. radiologic technologists and to compare dose between general radiologic technologists and those specializing in nuclear medicine procedures. Materials and Methods Annual personal dose equivalents (referred to as doses) from 1980 to 2015 were summarized for 58 434 (62%) participants in the U.S. Radiologic Technologists (USRT) cohort who responded to the most recent mailed work history survey (years 2012-2014) and reported never regularly performing interventional procedures. Doses were partitioned according to the performance of nuclear medicine (yes or no, frequency, procedure type) by calendar year. Annual dose records were described by using summary statistics (eg, median and 25th and 75th percentiles). Results Median annual doses related to performance of general radiologic procedures decreased from 0.60 mSv (interquartile range [IQR], 0.10-1.9 mSv) in 1980 to levels below the limits of detection by 2015, whereas annual doses related to performance of nuclear medicine procedures remained relatively high during this period (median, 1.2 mSv; IQR, 0.12-3.0 mSv). Higher median annual doses were associated with more frequent (above vs below the median) performance of diagnostic nuclear medicine procedures (≥35 vs <35 times per week; 1.6 mSv [IQR, 0.30-3.3 mSv] and 0.9 mSv [IQR, 0.10-2.6 mSv]). Higher and more variable annual doses were associated with more frequent performance of cardiac nuclear medicine (≥10 times per week) and PET (nine or more times per week) examinations (median, 1.6 mSv [IQR, 0.30-2.2 mSv] and 2.2 mSv [IQR, 0.10-4.6 mSv], respectively). Conclusion Annual doses to U.S. radiologic technologists performing general radiologic procedures declined during a 36-year period. However, consistently higher and more variable doses were associated with the performance of nuclear medicine procedures, particularly cardiac nuclear medicine and PET procedures. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Mettler and Guiberteau in this issue.

OCCUPATIONAL EXPOSURE CHARACTERISTICS AND FACTORS ASSOCIATED WITH RADIATION DOSES AMONG KOREAN RADIATION WORKERS

This study identified occupational factors associated with radiation exposure in Korea. Survey data of 16 037 workers from 2016 to 2017, including lifestyle factors and occupational characteristics, were combined with the National Dose Registry. Higher average annual doses were observed in groups exhibiting health risk factors such as body mass index (BMI) and smoking. Average annual doses also differed according to occupational characteristics, including average daily working hours, use of radiation protection gear, calendar year of hiring and employment status. Moreover, the influence of different factors on radiation dose differed with occupations. In industrial radiography and nuclear power plants, average daily working hours were the most important factor determining worker radiation doses. In other occupations, such as education, industry and research, calendar year of hiring and duration of employment were the most important factors. This research indicates the need to consider the specific work procedures of occupations to determine exposure variations between or within facilities.

Thyroid cancer risks among medical radiation workers in South Korea, 1996-2015

BACKGROUND

Thyroid cancer rates, especially among children, are known to be increased by radiation exposure. However, little is known about the impact of chronic low-dose radiation exposure on thyroid cancer risk in adulthood. This study examined radiation effects on thyroid cancer rates as well as an overall evaluation of thyroid cancer risk among medical radiation workers.

METHODS

Data on all diagnostic medical radiation workers enrolled in the national dosimetry registry between 1996 and 2011 were linked with the cancer registry data through 2015. Standardized incidence ratios (SIRs) were used to compare the observed cancer incidence rates in this population to those for the general population while internal comparisons were used to estimate relative risks (RRs) for occupational history and excess relative risks (ERRs) were used to quantify the radiation dose-response relationship.

RESULTS

Overall, 827 thyroid cancer cases were reported among 93,922 medical radiation workers. Thyroid cancer SIRs were significantly higher than expected for both men (SIR 1.72, 95% confidence interval [CI] 1.53 to 1.91) and women (SIR 1.18, 95% CI 1.08 to 1.28). However, RRs for thyroid cancer by job title and duration of employment showed no particular pattern among diagnostic medical radiation workers. There were no indications of a significant dose effect on thyroid cancer rates for either men (ERR/100 mGy 0.07, 95% CI -0.38 to 0.53) or women (ERR/100 mGy -0.13, 95% CI -0.49 to 0.23). The findings were similar for different job titles or when limited to workers employed for at least one year.

CONCLUSIONS

While thyroid cancer incidence rates among Korean medical radiation workers were somewhat higher than those in the general population, there was no significant evidence that this increase was associated with occupational radiation dose. Additional follow-up together with consideration of other risk factors should provide useful information on thyroid cancer rates in this cohort.

Projected lifetime cancer risks from occupational radiation exposure among diagnostic medical radiation workers in South Korea

BACKGROUND

Timely assessment of cancer risk from current radiation exposure among medical radiation workers can contribute to the development of strategies to prevent excessive occupational radiation exposure. The purpose of the present study is to estimate the lifetime risk of cancers induced by occupational radiation exposure among medical radiation workers.

METHODS

Using estimated organ doses and the RadRAT risk assessment tool, the lifetime cancer risk was estimated among medical radiation workers who were enrolled in the Korean National Dose Registry from 1996 to 2011. Median doses were used for estimating the risk because of the skewed distribution of radiation doses. Realistic representative exposure scenarios in the study population based on sex, job start year, and occupational group were created for calculating the lifetime attributable risk (LAR) and lifetime fractional risk (LFR).

RESULTS

The mean estimated lifetime cancer risk from occupational radiation exposure varied significantly by sex and occupational group. The highest LAR was observed in male and female radiologic technologists who started work in 1991 (264.4/100,000 and 391.2/100,000, respectively). Female workers had a higher risk of radiation-related excess cancer, although they were exposed to lower radiation doses than male workers. The higher LAR among women was attributable primarily to excess breast and thyroid cancer risks. LARs among men were higher than women in most other cancer sites. With respect to organ sites, LAR of colon cancer (44.3/100,000) was the highest in male radiologic technologists, whereas LAR of thyroid cancer (222.0/100,000) was the highest in female radiologic technologists among workers who started radiologic practice in 1991. Thyroid and bladder cancers had the highest LFR among radiologic technologists.

CONCLUSIONS

Our findings provide an assessment of the potential cancer risk from occupational radiation exposure among medical radiation workers, based on current knowledge about radiation risk. Although the radiation-related risk was small in most cases, it varied widely by sex and occupational group, and the risk would be underestimated due to the use of median, rather than mean, doses. Therefore, careful monitoring is necessary to optimize radiation doses and protect medical radiation workers from potential health risks, particularly female radiologic technologists.

ESTIMATION OF ORGAN DOSES AMONG DIAGNOSTIC MEDICAL RADIATION WORKERS IN SOUTH KOREA

This study aimed to estimate the radiation organ doses from occupational exposure in 94 396 Korean medical radiation workers. Data on badge doses (i.e. personal dose equivalent at 10 mm) between 1996 and 2011 obtained from a national dosimetry registry, survey data from 2012 to 2013, and organ dose conversion coefficients provided by the International Commission on Radiological Protection (ICRP) were used for the estimation. The highest mean cumulative badge doses (26.87 mSv) were observed in radiologists, followed by radiologic technologists (15.96 mSv). Male workers exhibited higher mean cumulative badge doses, across occupational groups. The estimated organ doses showed similar trends with those of badge doses. Organs located outside the apron's coverage such as the thyroid showed higher mean organ doses than those protected by the apron. Our findings could contribute to future radiation epidemiologic studies to investigate health effects from occupational radiation exposure in Korea.

Assessing the health effects associated with occupational radiation exposure in Korean radiation workers: protocol for a prospective cohort study

INTRODUCTION

The cancer risk of radiation exposure in the moderate-to-high dose range has been well established. However, the risk remains unclear at low-dose ranges with protracted low-dose rate exposure, which is typical of occupational exposure. Several epidemiological studies of Korean radiation workers have been conducted, but the data were analysed retrospectively in most cases. Moreover, groups with relatively high exposure, such as industrial radiographers, have been neglected. Therefore, we have launched a prospective cohort study of all Korean radiation workers to assess the health effects associated with occupational radiation exposure.

METHODS AND ANALYSIS

Approximately 42 000 Korean radiation workers registered with the Nuclear Safety and Security Commission from 2016 to 2017 are the initial target population of this study. Cohort participants are to be enrolled through a nationwide self-administered questionnaire survey between 24 May 2016 and 30 June 2017. As of 31 March 2017, 22 982 workers are enrolled in the study corresponding to a response rate of 75%. This enrolment will be continued at 5-year intervals to update information on existing study participants and recruit newly hired workers. Survey data will be linked with the national dose registry, the national cancer registry, the national vital statistics registry and national health insurance data via personal identification numbers. Age-specific and sex-specific standardised incidence and mortality ratios will be calculated for overall comparisons of cancer risk. For dose-response assessment, excess relative risk (per Gy) and excess absolute risk (per Gy) will be estimated with adjustments for birth year and potential confounders, such as lifestyle factors and socioeconomic status.

ETHICS AND DISSEMINATION

This study has received ethical approval from the institutional review board of the Korea Institute of Radiological and Medical Sciences (IRB No. K-1603-002-034). All participants provided written informed consent prior to enrolment. The findings of the study will be disseminated through scientific peer-reviewed journals and be provided to the public, including radiation workers, via the study website (http://www.rhs.kr/) and onsite radiation safety education.

Occupational radiation exposure and its health effects on interventional medical workers: study protocol for a prospective cohort study

INTRODUCTION

Although fluoroscopically guided procedures involve a considerably high dose of radiation, few studies have investigated the effects of radiation on medical workers involved in interventional fluoroscopy procedures. Previous research remains in the early stages and has not reached a level comparable with other occupational studies thus far. Furthermore, the study of radiation workers provides an opportunity to estimate health risks at low doses and dose rates of ionising radiation. Therefore, the objectives of this study are (1) to initiate a prospective cohort study by conducting a baseline survey among medical radiation workers who involve interventional fluoroscopy procedures and (2) to assess the effect of occupational radiation exposure and on the overall health status through an in-depth cross-sectional study.

METHODS AND ANALYSIS

Intervention medical workers in Korea will be enrolled by using a self-administered questionnaire survey, and the survey data will be linked with radiation dosimetry data, National Health Insurance claims data, cancer registry and mortality data. After merging these data, the radiation organ dose, lifetime attributable risk due to cancer and the risk per unit dose will be estimated. For the cross-sectional study, approximately 100 intervention radiology department workers will be investigated for blood tests, clinical examinations such as ultrasonography (thyroid and carotid artery scan) and lens opacity, the validation of badge dose and biodosimetry.

ETHICS AND DISSEMINATION

This study was reviewed and approved by the institutional review board of Korea University (KU-IRB-12-12-A-1). All participants will provide written informed consent prior to enrolment. The findings of the study will be disseminated through peer-reviewed scientific journals, conference presentations, and a report will be submitted to the relevant public health authorities in the Korea Centers for Disease Control and Prevention to help with the development of appropriate research and management policies.