In recent years, the field of medical radiation protection has entered an era of drastic changes. In addition to international trends, it may also be related to the increased awareness of radiation and radiation effects among the Japanese people due to the Fukushima nuclear accident in March 2011. As a result, with the revision of laws and regulations, strict control is required for medical radiation safety management and management of radiation workers. As a recent movement on radiation protection, this article reviews the changes in the threshold dose and dose limit of the lens of the eye, medical radiation safety management due to revision of medical law enforcement regulations, diagnostic reference levels, domestic and international trends regarding gonad shielding during radiography, trends toward new ICRP recommendation, and risk communication from recent trends in medical radiation protection.

Purpose: The purpose of this study was to develop software for smooth dose management based on the Japan diagnostic reference levels (DRLs 2020) in the field of nuclear medicine. Method: Using the programming language Visual Basic for Applications (VBA), we implemented a function for calculating actual doses, a function for comparing doses at one’s own facility with those of DRLs 2020, a function for calculating appropriate doses for pediatric nuclear medicine examinations, and so on. In addition, we evaluated actual doses before and after the software implementation. Result: The software enabled easy calculation of actual doses and comparison with DRLs 2020 for smooth dose management. Furthermore, we were able to use the results of dose evaluation to determine the dosage at our facility and to use them as a reference for optimization. Conclusion: In the field of nuclear medicine, it is possible to manage doses in accordance with DRLs 2020 by introducing own software into our clinical practice.

Purpose: The aim of this study was to provide the information needed to optimise a nuclear accident to human resource development training programmes for radiological technologists (RTs) based on the experience of the Fukushima Daiichi nuclear power station (FDNPS) accident. Methods: A total of 330 respondents (availability rate: 56.5%) were obtained through a postal questionnaire survey of RTs in Fukushima Prefecture. The analysed items were the relationship between the individual attributes, subject’s experience in responding to the FDNPS accident, and subject’s records of participating in nuclear accident trainings before the FDNPS accident with regard to 1) “skills that need to be learnt (4 items)” and 2) “basic knowledge (4 items)” to respond to a nuclear accident. Results: Regarding 1), air ambient dose and body surface contamination measurements were significantly associated with the number of beds at a place of work at the time of the FDNPS accident. In addition, consultations on radiation exposure were significantly associated with the experience in responding to the FDNPS accident and the records of participating in nuclear accident trainings before the FDNPS accident. Regarding 2), knowledge of internal exposure was significantly related to the years of employment at the time of the FDNPS accident and the experience in responding to the FDNPS accident. Conclusion: By considering the results of this study, it should be possible to provide training programmes for a nuclear accident that are optimally tailored to the background of the RTs.

Purpose: In this study, to develop radiomitigators capable of the emergency medical care of patients involved in radiation accidents, we investigated the radiomitigative effects and their underlying mechanisms of indole compounds such as DIM, GRM, and INM. Methods: The human normal fibroblast cell line, MRC-5 cells were administered 0.1% DMSO or each indole compound at 10 µM within 50–60 minutes after X-irradiated with 0–4 Gy. Next, we evaluated the alteration in the number of alive cells, clonogenic potential, DNA double-strand breaks, DNA damage repair activities, and protein expression related to regulate the oxidative stress response. Results: Our results showed that DIM treatment suppressed radiation-induced decrease in the number of alive cells and clonogenic potential. Then, DIM treatment significantly decreased DNA double-strand breaks and highly increased Nrf2 via increased phospho-GSK-3β (Ser9) expression. These findings suggest that, in part, increased expression of p-GSK-3β (Ser9) by DIM treatment reduced DNA double-strand breaks via activation of Nrf2, resulting mitigated radiation-induced a decrease in the number of alive cells and clonogenic potential. Conclusion: Therefore, DIM, not GRM and INM, is a potential candidate for radiomitigators that can be applied to the radiation emergency medicine.

Purpose: Skin injury in patients due to radiation exposure has been a complication in percutaneous coronary intervention (PCI) for a long time. To the best of our knowledge, there have been no reports comparing radiation dose by treatment area with diagnostic reference levels (DRLs) 2020, although the radiation dose varies by treatment area in PCI. Methods: In this study, the treatment areas were classified into four segments (i.e., AHA #1–3, AHA #4, AHA #5–10, and AHA #11–15), and each segment was compared with DRLs 2020. This retrospective study included 984 consecutive patients with single-vessel disease and non-chronic total occlusion. PCI was performed on a single device. Results: The median radiation dose was 1640.8 mGy, and the radiation dose for AHA #4 was 2732.0 mGy, which was significantly higher than the other treatment areas (p<0.001). In AHA #4, the radiation dose increased due to the heavy use of the left cranial view, and the patient background contributed to the increased lesion complexity. Therefore, it was challenging to evaluate AHA #4 and the other treatment areas with a uniform DRL value. Conclusion: Establishing a subdivided index for each treatment area is crucial if DRLs are used as a reference during procedures and as a guide for dose optimization.

Purpose: It has been reported that the placement of protective equipment in female pelvic radiography is predominantly inadequate compared with that of male. We analyzed the actual situation of ovarian shielding by protective devices using X-ray, CT, and MR images obtained in the past, and evaluated the effectiveness of gonadal protection in female hip radiography. Methods: The ovaries were contoured in MR images and the pelvic bone was extracted by CT images. The MR/CT fusion images were created using a 3D workstation. The amount of physiological fluctuation in the ovarian location was measured. The fusion images in the ray-summation display were manually superimposed with the X-ray image, and the percentage of ovaries that could be shielded by the protective device was classified into four categories: (a) complete protection, (b) partial protection, (c) failure of protection, and (d) image retaking. Results: The mean and maximum ovarian fluctuations were 1.1 cm and 3.9 cm in the superior and inferior directions, respectively, and 0.7 cm and 2.0 cm in the left and right directions, respectively. The percentage of ovaries shielded was 18.9% for complete protection, 58.5% for partial protection, 15.1% for inadequate protection, and 7.5% for image retaking. Conclusion: The effectiveness of gonadal protection is low because the protective device could not cover the entire ovary in about 80% of the female hip radiographs.

Purpose: To verify the influence of the software version of the dose control system on the equivalent dose and effective dose calculation values. Methods: We performed chest CT and liver to pelvic CT imaging with a human phantom placed on a CT bed. After the imaging was completed, the radiation dose structured reports (RDSRs) generated by the equipment were transferred to several dose management systems with different software versions for equivalent dose and effective dose calculations. Results: The equivalent and effective doses calculated from the same RDSR differed depending on the software version of the dose management system with a difference of approximately 2 times for the effective dose and up to 50 times for the equivalent dose. Conclusion: It is considered that the voxel phantom geometry and dose calculation algorithm may differ depending on the software version of the dose management system. Careful attention should be paid in handling the dose calculation values because the exposure explanations and risk assessments using the equivalent doses, and effective dose calculated by the dose management systems may be overestimated.

Purpose: We aimed to clarify the error of displayed value against the measured value of the average glandular dose (AGD) in two-dimensional (2D) mammography and digital breast tomosynthesis (DBT) and evaluate the accuracy of the displayed AGD as an index to estimate AGD. Methods: Polymethyl methacrylate (PMMA) phantoms with thicknesses varying from 20 to 80 mm were imaged, and the values displayed on the mammography system were used as the displayed AGD. The incident air kerma and the half-valued layer were measured, and the measured AGD in 2D mammography was calculated using the equation by Dance et al. On the other hand, the measured AGD in DBT was calculated by correcting for different projection angles. The relative error to the PMMA thickness was evaluated by assessing the relative error of the displayed AGD against the measured AGD. Results: The maximum relative error of the displayed AGD against the measured AGD was 17.3% in 2D mammography, 19.1% in the standard (ST) mode, and 19.8% in the high-resolution (HR) mode. Conclusion: The relative error of the displayed AGD against the measured AGD tended to increase with increase in PMMA thickness. This tendency was especially noticeable for PMMA with thicknesses of 70 and 80 mm in DBT.

Purpose: X-ray CT examinations are required not only in routine medical examinations but also in various situations such as emergency medical care. Although medical staff may be exposed to radiation when assisting patients, the distribution of air-absorbed doses in the CT examination room when using a special protective shield for CT has not been clarified. Here, we measured air-absorbed doses at several points simultaneously to clarify the distribution of these doses and the effect of a special protective shield for CT in reducing them. Method: A human phantom was imaged with an X-ray CT system. The absorbed dose in the air dose profile distribution was measured with an OSL dosimeter in the presence and absence of a special protective shield for CT. Results: The highest air absorbed doses of 4.27 mGy were at 0 cm in the horizontal direction, 120 cm in the vertical direction, and 50 cm in the body axis direction. The largest reduction in air absorbed dose following installation of the special protective shield for CT was 91.7%, obtained at 0 cm in the horizontal direction, 150 cm in the vertical direction, and 50 cm in the body axis direction. Conclusion: A 91.7% reduction in air-absorbed dose was o directly behind the special protective shield for CT. The reduction in air-absorbed dose was 65.8% at the location of a gap between the special protective shield for CT and gantry.

Purpose: The purpose of this study was to evaluate the accuracy of incident air kerma (K_a,r) and air kerma-area product (P_KA) displayed on over-couch-type X-ray fluoroscopic systems by comparing them with the measured values. Methods: An ionizing chamber was placed at the patient entrance reference point to measure the K_a,r. The P_KA was calculated by multiplying the K_a,r by the irradiation area. These measured values were compared with the displayed values. Results: The differences between measured and displayed K_a,r and P_KA were less than ±35%, which was the criteria of the Japanese Industrial Standards (JIS). However, the accuracy of the displayed values differed depending on the manufacturer and the device. Conclusion: Although no error exceeding the JIS criteria was observed, it is necessary to understand the characteristics of the X-ray fluoroscopic systems related to displayed dose and to manage the systems by performing dose measurements periodically.