Improving radiation dosimetry with an automated micronucleus scoring system: correction of automated scoring errors.

Radiation dose estimations performed by automated counting of micronuclei (MN) have been studied for their utility for triage following large-scale radiological incidents; although speed is essential, it also is essential to estimate radiation doses as accurately as possible for long-term epidemiological follow-up. Our goal in this study was to evaluate and improve the performance of automated MN counting for biodosimetry using the cytokinesis-block micronucleus (CBMN) assay. We measured false detection rates and used them to improve the accuracy of dosimetry. The average false-positive rate for binucleated cells was 1.14%; average false-positive and -negative MN rates were 1.03% and 3.50%, respectively. Detection errors seemed to be correlated with radiation dose. Correction of errors by visual inspection of images used for automated counting, called the semi-automated and manual scoring method, increased accuracy of dose estimation. Our findings suggest that dose assessment of the automated MN scoring system can be improved by subsequent error correction, which could be useful for performing biodosimetry on large numbers of people rapidly, accurately, and efficiently.

Reliability and Validity of a Nationwide Survey (the Korean Radiation Workers Study).

BACKGROUND: This study aimed to evaluate the reliability and validity of the self-administered questionnaire for Korean radiation workers. METHODS: From May 24, 2016, to June 30, 2017, 20,608 participants completed the questionnaire, providing information on sociodemographics, lifestyle, work history and practices, medical radiation exposure, and medical history, which was linked to the National Dose Registry and the National Cancer Registry. The validity of the questionnaire was evaluated using the responses of 20,608 workers, and reliability was evaluated using the responses of 3043 workers who responded to the survey twice. RESULTS: Responses concerning demographic characteristics and lifestyle showed reliability with a moderate-to-high agreement (kappa: 0.43-0.99), whereas responses concerning occupation and medical radiation exposure had a wide range of agreement (kappa: 0.05-0.95), possibly owing to temporal variability during employment. Regarding validity, responses to the question about the first year of employment had an excellent agreement with the national registry (intraclass correlation coefficient = 0.9); however, responses on cancer history had a wide range of agreement (kappa: 0.22-0.85). CONCLUSION: Although the reliability and validity of the questionnaire were not distinguished by demographic characteristics, they tended to be low among participants whose occupational radiation exposure was minimal. Overall, the information collected can be reliable for epidemiological studies; however, caution must be exercised when using information such as medical exposure and work practices, which are prone to temporal variability.

Non-cancer disease prevalence and association with occupational radiation exposure among Korean radiation workers.

Radiation-induced cancer risks have known stochastic effects; however, regarding non-cancer diseases, evidence of risk at low radiation doses remains unclear. We aimed to identify underlying characteristics concerning non-cancer disease prevalence and determine associations with radiation dose among Korean radiation workers. Using a nationwide baseline survey, 20,608 workers were enrolled. Data concerning participant demographics, occupational characteristics, lifestyle, and lifetime prevalence of non-cancer diseases were linked to a national dose registry. We compared non-cancer disease prevalences in the Korean general population with those in this cohort and undertook a dose-response analysis concerning the cumulative dose. Hyperlipidemia (10.6%), circulatory (9.6%), and respiratory (4.1%) system diseases, followed by thyroid diseases (3.5%), had the highest prevalences, with hyperlipidemia, thyroid diseases, and hepatitis prevalence being higher in the cohort than in the general population. Radiation doses were associated with elevated prevalences of most diseases; however, associations were attenuated and not significant after adjusting for confounders, except for musculoskeletal system diseases (prevalence odds ratio [POR]/10 mSv, 1.03; 95% confidence interval [CI] 1.00-1.07) and cataracts (POR/10 mSv, 1.04; 95% CI 1.00-1.07). Further studies are warranted to investigate the causality of those non-cancer diseases involving more varied confounders such as physical and psychosocial stresses and ultraviolet light.

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.

Assessment of an Emergency Medicine System for Radiation Accidents in Korea: A State Survey of the Workers Involved the Medical Response to Radiation Accidents.

Radiation emergency medicine systems are operated around the world to provide special care for the injured that require immediate medical attention in accidents. The objective of this survey was to evaluate people's perception of those who design the emergency medical plan for radiation accidents and those who supervise it in Korea. A questionnaire survey was conducted on the people involved in a regulatory system for medical response in a radiation emergency. Of 150 survey recipients, 133 (88.7%) completed the survey, including 92 workers and 41 inspectors. The respondents expressed the view that the national emergency medical plan is prepared above the average level using a Likert-style scale of 1 to 5 (mean = 3.55, SD = 0.74). Interestingly, using the Mann-Whitney U test, it could be shown that inspectors evaluated the emergency medical system for radiation accidents more strictly in all of the questions than the licensee workers, especially on radiation medical emergency preparedness (p = 0.004) and the governmental regulatory policy for radiation safety (p = 0.007). For a more efficient system of radiation emergency medicine, licensee workers prioritized the workforce, whereas inspectors favored laws and regulations for safety. The survey results show different perspectives between inspectors and licensee workers, which stem from the actual properties of each occupational role in the regulatory system for radiation medical emergency. These data could be utilized for communication and interaction with relevant people to improve the medical response preparedness against radiation accidents.

Interventional radiologists have a higher rate of chromosomal damage due to occupational radiation exposure: a dicentric chromosome assay.

OBJECTIVES: There are growing concerns regarding radiation exposure in medical workers who perform interventional fluoroscopy procedures. Owing to the nature of certain interventional procedures, workers may be subjected to partial-body radiation exposure that is high enough to cause local damage. We aimed to investigate the level of radiation exposure in interventional radiologists in South Korea by performing cytogenetic biodosimetry, particularly focusing on partial-body exposure. METHODS: Interventional radiologists (n = 52) completed a questionnaire, providing information about their work history and practices. Blood samples were collected and processed for a dicentric chromosome assay. We determined Papworth's U-value to assess the conformity of dicentrics with the Poisson distribution to estimate the partial-body exposures of the radiologists. RESULTS: Radiologists had a higher number of dicentrics than the normal population and industrial radiographers. Indeed, subjects with a U-value of > 1.96, an indicator of heterogeneous exposure, were observed more frequently; 4.67 ± 0.81% of their body was irradiated at an average dose of 4.64 ± 0.67 Gy. Logistic regression analysis revealed that the total duration of all interventional procedures per week was associated with partial-body exposure levels. CONCLUSIONS: Our findings suggest that interventional radiologists had greater chromosomal damages than those in other occupational groups, and their partial-body exposure levels might be high enough to cause local damage. Use of special dosimeters to monitor partial-body exposure, as well as restricting the time and frequency of interventional procedures, could help reduce occupational radiation exposure. KEY POINTS: • Interventional radiologists had a higher number of dicentrics than the normal population and industrial radiographers. • The level of partial-body exposure of interventional radiologists might be high enough to cause occupational local damage such as a skin cancer in fingers. • Restricting the duration and frequency of interventional procedures might be helpful in reducing occupational radiation exposure.

Increased Incidence of Thyroid Cancer in Occupational Radiation Epidemiology: Attribution to Screening among Radiation Workers.

In most studies on radiation workers, the incidence of thyroid cancer was determined to be higher than among the general population; this is generally assumed to be due to overdiagnosis through thyroid screening. However, there is a lack of evidence on the association between thyroid screening and increased thyroid cancer incidence in most occupational studies. In this study, we compared thyroid cancer screening rates between the general population and radiation workers with various occupations and examined the relationship between these rates and thyroid cancer incidence. We compared thyroid screening rates between radiation workers and the general population with age- and sex-standardized screening ratios (SSRs) using data from two national surveys conducted during 2015-2017 in Korea, and assessed the correlation between these ratios and age- and sex-standardized incidence ratios (SIRs) for thyroid cancer. Screening rates were higher among radiation workers than among the general population, with an overall SSR of 1.58 (95% confidence interval: 1.54-1.62). When various types of occupations were compared, those with an increased SSR also had an increased SIR. SSRs remained high even when the screening period was restricted to the year preceding the survey (the year after the establishment of guidelines for thyroid cancer screening aimed at reducing overdiagnosis). In conclusion, the increased incidence of thyroid cancer among radiation workers compared to that among the general population can be attributed mainly to increased thyroid screening rates. Additional efforts are needed to reduce unnecessary thyroid cancer screening in occupational populations, particularly in those with better access to healthcare, in terms of clinical rationale and for assessing the true increase in thyroid cancer incidence.

Risk perception of radiation emergency medical staff on low-dose radiation exposure: Knowledge is a critical factor.

Radiation emergency medical (REM) staff respond to many types of disasters such as radiological and nuclear accidents as well as environmental radioactivity exposure. The objective of this study was to evaluate the risk perception of REM staff on radiation exposure in various situations and to analyze the factors that affect their risk perception. A questionnaire was given to 284 REM staff affiliated with various organizations, including nuclear power generation, nuclear fuel manufacturing, large-scale irradiation, and radiation-waste disposal facilities, as well as research and development institutions. To determine the substantially influential factors for risk perception, we analyzed the questionnaire responses using ordinal logistic regression, Kruskal-Wallis, and Spearman correlation analyses. It was generally perceived by REM staff that low-dose radiation exposure in daily life and work environments does not pose any health risks. A higher level of radiation knowledge was tightly associated with a lower risk perception of REM staff on extremely low-dose (several mSv) radiation exposure, thus exhibiting an inverse correlation. In contrast to radiation researchers, the work experience of REM staff was not a contributing factor to their risk perception. In our study, REM staff with a high level of radiation knowledge did not have any health concerns in their work environments. Efforts to enhance the radiation knowledge of REM staff through proper education and training would result in analytical risk evaluation, which may also improve their willingness to help meet surge capacity needs in large-scale radiological events.

Organ-Specific Effects of Low Dose Radiation Exposure: A Comprehensive Review.

Ionizing radiation (IR) is a high-energy radiation whose biological effects depend on the irradiation doses. Low-dose radiation (LDR) is delivered during medical diagnoses or by an exposure to radioactive elements and has been linked to the occurrence of chronic diseases, such as leukemia and cardiovascular diseases. Though epidemiological research is indispensable for predicting and dealing with LDR-induced abnormalities in individuals exposed to LDR, little is known about epidemiological markers of LDR exposure. Moreover, difference in the LDR-induced molecular events in each organ has been an obstacle to a thorough investigation of the LDR effects and a validation of the experimental results in in vivo models. In this review, we summarized the recent reports on LDR-induced risk of organ-specifically arranged the alterations for a comprehensive understanding of the biological effects of LDR. We suggested that LDR basically caused the accumulation of DNA damages, controlled systemic immune systems, induced oxidative damages on peripheral organs, and even benefited the viability in some organs. Furthermore, we concluded that understanding of organ-specific responses and the biological markers involved in the responses is needed to investigate the precise biological effects of LDR.

Rogue cell-like chromosomal aberrations in peripheral blood lymphocytes of interventional radiologists: A case study.

We report two cases of interventional radiologists who had been exposed to radiation while performing fluoroscopically-guided interventional procedures (FGIPs), mainly transcatheter arterial chemoembolization, percutaneous catheter drainage, and percutaneous transhepatic biliary drainage procedures, for over 10 years. They had a unique multi-aberrant cell type with not only high numbers of dicentrics and/or centric rings but also excess acentric double minutes, similar to a rogue cell. As revealed in a self-administered questionnaire, they wore personal dosimeters and protective equipment at all times and used shielding devices during interventional fluoroscopy procedures. However, the exposed dose levels derived from cytogenetic dosimetry were much higher than the doses recorded on their personal dosimeters. A large number of unstable and stable chromosomal aberrations that were found in the peripheral blood lymphocytes of these interventional radiologists might be due to repeated and long-term exposure to ionizing radiation while performing FGIPs. Further investigations of chromosomal aberrations in interventional radiologists may improve the understanding of the long-term effects of radiation exposure on medical personnel.

The Emerging Roles of Exosomes as EMT Regulators in Cancer.

Epithelial-mesenchymal transition (EMT) causes epithelial cells to lose their polarity and adhesion property, and endows them with migratory and invasive properties to enable them to become mesenchymal stem cells. EMT occurs throughout embryonic development, during wound healing, and in various pathological processes, including tumor progression. Considerable research in the last few decades has revealed that EMT is invariably related to tumor aggressiveness and metastasis. Apart from the interactions between numerous intracellular signaling pathways known to regulate EMT, extracellular modulators in the tumor microenvironment also influence tumor cells to undergo EMT, with extracellular vesicles (EVs) receiving increasing attention as EMT inducers. EVs comprise exosomes and microvesicles that carry proteins, nucleic acids, lipids, and other small molecules to stimulate EMT in cells. Among EVs, exosomes have been investigated in many studies, and their role has been found to be significant with respect to regulating intercellular communications. In this review, we summarize recent studies on exosomes and their cargoes that induce cancer-associated EMT. Furthermore, we describe the possible applications of exosomes as promising therapeutic strategies.

A Cohort Study of Korean Radiation Workers: Baseline Characteristics of Participants.

The Korean Radiation Worker Study investigated the health effects of protracted low-dose radiation among nuclear-related occupations in the Nuclear Safety and Security Commission in Korea. From 2016-2017, 20,608 workers were enrolled (86.5% men and 30.7% nuclear power plant workers). The mean cumulative dose ± standard deviation between 1984 and 2017 (1st quarter) was 11.8 ± 28.8 (range 0-417) mSv. Doses below recording level (≤0.1 mSv) were reported in 7901 (38.3%) cases; 431 (2%) had cumulative doses ≥100 mSv. From 1999-2016, 212 cancers (189 men, 23 women) occurred; thyroid cancer predominated (39.2%, 72 men, 11 women). In men, the standardized incidence ratio (SIR) for all cancers was significantly decreased (SIR = 0.76, 95% CI 0.66-0.88); however, that for thyroid cancer was significantly increased (SIR = 1.94, 95% CI 1.54-2.44). Compared to the non-exposed group (≤0.1 mSv), the relative risk (RR) in the exposed group (>0.1 mSv) after adjusting for sex, attained age, smoking status, and duration of employment was 0.82 (95% CI 0.60-1.12) for all cancers and 0.83 (95% CI 0.49-1.83) for thyroid cancer. The preliminary findings from this baseline study with a shorter follow-up than the latency period for solid cancer cannot exclude possible associations between radiation doses and cancer risk.

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.

Evaluation of performance characteristics of portal monitor for radiation emergency.

For evaluating the counting efficiency of a portal monitor, we use a137Cs radiation point source (1 µCi) to subsequently establish it effective measurable area. Through simulation, we estimate the appropriate distance from potentially contaminated individuals in the scanning queue to the monitoring individual. When this distance is over 10 m, the counting efficiency was below 0.01%. We find that the triage can be applied to roughly 180 individuals per hour during mass casualties.

Adding Ovarian Suppression to Tamoxifen for Premenopausal Breast Cancer: A Randomized Phase III Trial.

PURPOSE: The addition of ovarian function suppression (OFS) for 5 years to tamoxifen (TAM) for treatment of premenopausal patients with breast cancer after completion of chemotherapy has beneficial effects on disease-free survival (DFS). This study evaluated the efficacy of adding 2 years of OFS to TAM in patients with hormone receptor-positive breast cancer who remain in a premenopausal state or resume ovarian function after chemotherapy. PATIENTS AND METHODS: We enrolled 1,483 premenopausal women (age ≤ 45 years) with estrogen receptor-positive breast cancer treated with definitive surgery after completing adjuvant or neoadjuvant chemotherapy. Ovarian function was assessed every 6 months for 2 years since enrollment on the basis of follicular-stimulating hormone levels and vaginal bleeding history. If ovarian function was confirmed to be premenopausal at each visit, the patient was randomly assigned to complete 5 years of TAM alone (TAM-only) group or 5 years of TAM with OFS for 2 years that involved monthly goserelin administration (TAM + OFS) group. DFS was defined from the time of enrollment to the time of the first event. RESULTS: A total of 1,293 patients were randomly assigned, and 1,282 patients were eligible for analysis. The estimated 5-year DFS rate was 91.1% in the TAM + OFS group and 87.5% in the TAM-only group (hazard ratio, 0.69; 95% CI, 0.48 to 0.97; P = .033). The estimated 5-year overall survival rate was 99.4% in the TAM + OFS group and 97.8% in the TAM-only group (hazard ratio, 0.31; 95% CI, 0.10 to 0.94; P = .029). CONCLUSION: The addition of 2 years of OFS to TAM significantly improved DFS compared with TAM alone in patients who remained premenopausal or resumed ovarian function after chemotherapy.

Validation of the dicentric chromosome assay for radiation biological dosimetry in South Korea.

The dicentric chromosome assay (DCA) is a well-established biodosimetry test to estimate exposure to ionizing radiation. The Korea Institute of Radiological and Medical Sciences (KIRAMS) established a DCA protocol as a medical response to radiation emergencies in South Korea. To maintain its accuracy and performance, intercomparison exercises with Health Canada (HC) have been conducted; herein, we aimed to validate our capacity of DCA analysis based on those results. Blood samples irradiated at HC were shipped to KIRAMS to assess the irradiation dose to blinded samples using conventional DCA full scoring and triage-based techniques (conventional DCA scoring in triage mode and DCA QuickScan method). Actual doses fell within the 95% confidence intervals of dose estimates for 70-100% of the blinded samples in 2015-2018. All methods discriminated binary dose categories, reflecting clinical significance. This DCA can be used as a reliable radiation biodosimetry tool in preparation for radiation accidents in South Korea.

Health Effects of Radon Exposure.

Radon is a naturally occurring radioactive material that is formed as the decay product of uranium and thorium, and is estimated to contribute to approximately half of the average annual natural background radiation. When inhaled, it damages the lungs during radioactive decay and affects the human body. Through many epidemiological studies regarding occupational exposure among miners and residential exposure among the general population, radon has been scientifically proven to cause lung cancer, and radon exposure is the second most common cause of lung cancer after cigarette smoking. However, it is unclear whether radon exposure causes diseases other than lung cancer. Media reports have often dealt with radon exposure in relation to health problems, although public attention has been limited to a one-off period. However, recently in Korea, social interest and concern about radon exposure and its health effects have increased greatly due to mass media reports of high concentrations of radon being released from various close-to-life products, such as mattresses and beauty masks. Accordingly, this review article is intended to provide comprehensive scientific information regarding the health effects of radon exposure.

Mapping the research trends on the biological effects of radiation less than 100 mSv: a bibliometric analysis for 30 years publication.

PURPOSE: The purpose of this study is to evaluate the global scientific publication of biological research of low dose radiation for the past 30 years and provide the insights into the characteristics of research activities and major topics regarding biological effects of low dose radiation exposure. MATERIALS AND METHODS: We bibliometrically investigated the biological research publication of radiation exposure less than 100 mSv. References published from 1987 to 2016 were achieved from the Scopus database and filtered by several criteria such as publication types, research fields, and radiation dose range. RESULTS: Total 753 references were assembled for the bibliometric analysis on the biological studies of radiation effect less than 100 mSv. It provided fundamental knowledge of research, including production tendency, contribution, impact journals, and major research themes. Based on the keyword analysis, we found that specific topics on the biological response to radiation exposure have been changed from the examination of low dose radiation-induced phenomena to the investigation of how to induce a physiological response. In addition, featured articles showed the various views on the biological effects of radiation less than 100 mSv in 30 years publication, depending on radiation doses and types. CONCLUSIONS: Continuous studies in large programs of low dose radiation led to the increment of research achievements in accordance with societal needs in radiation safety regulation for health protection. Our findings can surely help radiation researchers to gain insights and penetration in low dose risk research for radiation protection, and establish a further research direction.

Health effects of exposure to radon: implications of the radon bed mattress incident in Korea.

Radon is a naturally occurring radioactive material formed by the slow decay of uranium and thorium found in the earth's crust or construction materials. Internal exposure to radon accounts for about half of the natural background radiation dose to which humans are exposed annually. Radon is a carcinogen and is the second leading cause of lung cancer following smoking. An association between radon and lung cancer has been consistently reported in epidemiological studies on mine workers and the general population with indoor radon exposure. However, associations have not been clearly established between radon and other diseases, such as leukemia and thyroid cancer. Radiation doses are assessed by applying specific dose conversion coefficients according to the source (e.g., radon or thoron) and form of exposure (e.g., internal or external). However, regardless of the source or form of exposure, the effects of a given estimated dose on human health are identical, assuming that individuals have the same sensitivity to radiation. Recently, radiation exceeding the annual dose limit of the general population (1 mSv/yr) was detected in bed mattresses produced by D company due to the use of a monazite-based anion powder containing uranium and thorium. This has sparked concerns about the health hazards for mattress users caused by radiation exposure. In light of this event, this study presents scientific information about the assessment of radon and thoron exposure and its human implications for human health, which have emerged as a recent topic of interest and debate in society.