Organ dose reconstruction for the radiation epidemiological study of Korean radiation workers: the first dose evaluation for the Korean Radiation Worker Study (KRWS)

Characterization of backscatter factors for various tissue substitutes in diagnostic radiology: a Monte Carlo investigation

Accurate assessment of backscatter factors (BSFs) is critical in medical dosimetry to precisely quantify the increase in surface dose caused by photon scattering, particularly in the low-energy kilovoltage X-ray beams used in diagnostic radiology. This study aimed to conduct a comprehensive evaluation of BSF values for diagnostic X-ray beams through Monte Carlo simulations. The interactions of BSFs with widely used tissue substitutes, including water, ICRU tissue, polyester, polymethyl methacrylate (PMMA), and nylon, were examined across a range of conditions, including half-value layer (HVL), field size, and energy spectra. The results demonstrate that BSF values consistently increase with larger field sizes and higher beam energies/HVLs, highlighting the significant impact of these parameters on scatter contributions. Comparative analysis of the materials revealed that water most closely approximates the BSF behaviour of ICRU tissue, with deviations of -2.08-8% across the studied energy range and field sizes. Polyester and PMMA also showed promising agreement, converging to within ± 5% of ICRU tissue at higher energies and larger field sizes. In contrast, nylon exhibited more substantial deviations, particularly in smaller field sizes and lower energies. These findings provide essential insights to improve the accuracy of dosimetric models and enhance radiation safety in diagnostic radiology applications.

Risks of Circulatory Diseases among Korean Radiation Workers Exposed to Low-dose Radiation

High-dose radiation has been widely recognized as a risk factor for circulatory diseases. There is increasing evidence for risk of circulatory diseases in response to low and moderate radiation doses in recent years, but the results are not always consistent. We aimed to evaluate the associations between low-dose radiation exposure (<0.1 Gy) and the incidence of circulatory disease in a large cohort of Korean radiation workers. We collected data from a cohort of 187,001 radiation workers monitored for personal radiation dose since 1984 and linked with the National Health Insurance Service data from 2002 to 2021. Excess relative risks (ERRs) per 100 mGy were calculated to quantify the radiation dose-response relationship. The mean duration of follow-up was 13.3 years. A total of 12,705 cases of cerebrovascular disease (CeVD) and 19,647 cases of ischemic heart disease (IHD) were diagnosed during the follow-up period (2002-2021). The average cumulative heart dose was 4.10 mGy, ranging from 0 to 992.62 mGy. The ERR per 100 mGy with 10-year lagged cumulative heart doses was estimated at -0.094 (95% CI -0.248, 0.070) for CeVD and -0.173 (95% CI -0.299, -0.041) for IHD. The ERRs were not significantly changed after adjusting for confounding factors such as smoking, income, blood pressure, body mass index, and blood glucose level. A linear quadratic model was found to provide a better fit for the ERR of CeVD and IHD than a linear model (P = 0.009 and 0.030, respectively). There were no statistically significant variations in ERR/100 mGy estimates for either CeVD or IHD in terms of sex, attained age, and duration of employment; however, heterogeneity in the ERR/100 mGy estimates for CeVD among occupations was observed (P = 0.001). Our study did not find conclusive evidence supporting the association between occupational low-dose radiation and an increased risk of circulatory diseases. The significant negative ERR estimates for IHD need further investigation with a more extended follow-up period.