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—It has been challenging to obtain reliable estimates of thyroid equivalent doses (TEDs) to residents involved in the 11 March 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident because of the shortage of direct human measurements associated with 131I, the largest contributor to the dose of concern. The present study attempted to perform the estimation of the TEDs by inhalation of 131I to residents from Namie-town, one of the most radiologically-affected municipalities, by means of the latest atmospheric transport and dispersion model (ATDM) simulations with the Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) ver. 2, coupled with personal behavioral data containing the history of the whereabouts of individuals shortly after the accident. We analyzed 1,637 residents who underwent direct measurements with whole-body counters several months after the accident and provided their personal behavioral data. We divided the subjects into two groups based on whether the distances between their locations and the FDNPP were >20 km as of 15:00 on 12 March in relation to the timepoint of the hydrogen explosion at the Unit 1 Reactor building. As a result, the 90th percentile TEDs of the 1,249 prompt evacuees and 388 late evacuees were 3.9 mSv (adult)–6.8 mSv (10-y-old) and 24.1 mSv (adult)–35.6 mSv (5-y-old), respectively, excluding 16 persons whose TEDs exceeded 50 mSv. The 90th percentile (median) TEDs to 1-y-old children (not included in the subjects) for the prompt and late evacuation groups were 8.1 (1.0) mSv and 36.3 (19.7) mSv, respectively. Additionally, this study provided the evidence to support the view that the explosive event at the Unit 1 Reactor building on the afternoon of 12 March 2011 could have caused the critical group among Namie-town's residents, whereas the largest release event on 15 March gave relatively small doses to the residents because their exposure took place mostly at sites that were distant from the FDNPP. However, the present dose estimation has potentially large uncertainty at the individual level; further validations are thus necessary.

More than 9 y have passed since the 2011 nuclear disaster in Fukushima Prefecture, Japan. During this period, much effort has been spent on the dose reconstruction for Fukushima residents; however, the estimation of the internal dose due to the potential intake of the short-lived radionuclides (mainly iodine-131) has been challenging because of the lack of direct human measurements at the early phase of the accident. Our previous study revealed that the residual cesium body contents observed in delayed whole-body counter (WBC) measurements of residents from Namie-town, one of the most affected municipalities, varied greatly with the timepoint of their evacuations on 12 March 2011 when the first explosive event occurred at the accident site; i.e., the late evacuees had much higher residual cesium body contents compared to the prompt evacuees. The present study thus aimed to clarify this finding by reproducing the exposure situation based on the evacuees' personal behavioral data in combination with the latest atmospheric transport and dispersion model (ATDM) simulation for 356 selected subjects in adult and 15-y (13-17 y) age groups. The results demonstrated that the ATDM simulation-based method could reasonably reproduce the subjects' exposure situation, supporting the previous finding. However, the residual cesium-137 body contents calculated by this method were only 10%-20% of those in the subjects' WBC measurements. This large discrepancy was considered to be caused by both the present method's underestimation and the overestimation of the subjects' early intake in the WBC measurements due to a conservative intake scenario not assuming potential additional intake. Additional studies are needed to further clarify the reasons for the discrepancy and to evaluate the magnitude of the inhalation dose in the accident.

More than nine years have passed since the 2011 nuclear disaster in Fukushima Prefecture, Japan. During this period, much effort has been made on the dose reconstruction for Fukushima residents; however, the estimation of the internal dose due to the potential intake of the short-lived radionuclides (mainly, 131I) has been challenging because of the lack of direct human measurements at the early phase of the accident. Our previous study revealed that the residual cesium body contents observed in delayed whole-body counter (WBC) measurements of residents from Namie-town, one of the most affected municipalities), varied greatly with the timepoint of their evacuations on 12 March 2011 when the first explosive event occurred at the accident site; i.e., the late evacuees had much higher residual Cs body contents compared to the prompt evacuees. The present study thus aimed to clarify this finding by reproducing the exposure situation based on the evacuees' personal behavioral data in combination with the latest atmospheric transport and dispersion model (ATDM) simulation for 356 selected subjects in adult and 15-year (13–17 yrs) age groups. The results demonstrated that the ATDM simulation-based method could reasonably reproduce the subjects' exposure situation, supporting the previous finding. However, the residual 137Cs body contents calculated by this method were only 10%–20% of those in the subjects' WBC measurements. This large discrepancy was considered to be caused by both the present method's underestimation and the overestimation of the subjects' early intake in the WBC measurements due to a conservative intake scenario not assuming potential additional intake. Additional studies are needed to further clarify the reasons for the discrepancy and to evaluate the magnitude of the inhalation dose in the accident.

Background: Huge amounts of radionuclides were released into the environment due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, which caused not only serious contamination on the ground, but also radiation exposure to the public. One problem that remains in performing the dose estimation is the difficulty of estimating the internal thyroid dose due to the intake of radioiodine (mainly, 131I) because of limitations to the human data available. Materials and Methods: The relevant papers were collected and reviewed by the authors. The results of thyroid dose estimates from different studies were tabulated for comparison. Results and discussion: The thyroid dose estimates from the studies varied widely. The dose estimates by the United Nations Scientific Committee on the Effects of Atomic Radiation were higher than the others due to the ingestion dose being based on conservative assumptions. The dose estimates by Japanese experts were mostly below 20‒30 mSv. The recent studies suggested that exposure on 12 March would be crucial for late evacuees from the areas near the FDNPP because of the possible intake of short-lived radionuclides other than 131I. Further multilateral studies are vital to reduce uncertainties in the present dose estimations. Conclusion: The estimation of the thyroid doses to Fukushima residents still has many uncertainties. However, it is considered unlikely that the thyroid doses exceeded 50 mSv except in some extreme cases. Further multilateral studies are thus necessary to reduce the uncertainties in the present dose estimations.

Estimating the internal thyroid dose received by residents involved in the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has been a challenging task because of the shortage of direct human measurements related to the largest contributing radioisotope to the dose, I. In a previous dose estimation, we used the results of whole-body counter (WBC) measurements targeting Cs and Cs, based on the assumption that these radioisotopes were incorporated at the same time as I in the early phase of the accident. The main purpose of this study was to clarify whether the trace of the early intake remained in the WBC measurements that were started several months after the accident. In the present work, WBC data of 1,639 persons from Namie town, one of the heavily contaminated municipalities, were analyzed together with their evacuation behavior data. The results demonstrated that the cesium detection rate in the WBC results was several times higher in the late evacuees [who evacuated outside the 20-km radius of the FDNPP at 3:00 p.m. (Japanese Local Time) on 12 March or later] compared to the prompt evacuees (who evacuated before 3:00 p.m. on 12 March). Among the adults, the cesium detection rates (and the 90th percentile values of the Cs intake) of the prompt and late evacuees were about 20% (5.4 × 10 Bq) and 60% (1.6 × 10 Bq), respectively. Approximately 20% of the individuals analyzed were categorized as late evacuees. These differences in cesium would be caused by exposure to the radioactive plume in the afternoon on 12 March, which was likely to influence the late evacuees. On the other hand, the intake on 15 March, when the largest release event occurred, was expected to be relatively small for Namie town's residents. In conclusion, the trace of the early intake remained in the WBC measurements, although this would not necessarily be true for all subjects. The results obtained from this study would provide useful information for the reconstruction of the early internal thyroid doses from radioiodine in the future.

The national system for radiation emergency medicine in Japan was revised based on the lessons learned from the Fukushima Daiichi Nuclear Power Plant accident. This system was further revised in 2019; specifically, the Nuclear Regulation Authority of Japan designated the National Institutes for Quantum Science and Technology (QST) as the national core center for coordinating and guiding four other Advanced Radiation Emergency Medical Support Centers. These centers will be responsible for providing medical treatments of severely exposed or contaminated patients as well as maintaining human resources to respond to nuclear disaster through a wide variety of training courses. Diagnostic dose assessment for patients is also one of the important missions of the centers. To enhance the capability for dose assessment of patients internally contaminated with actinides, the QST started operation of a new facility named the Dose Assessment Building for Advanced Radiation Emergency Medicine. A new bioassay laboratory was installed at this facility as well as an integrated in-vivo counter (Tamakuma et al., this issue). This laboratory has two rooms for pretreatment of excreta samples equipped with ashing, digestion and purification devices, and one analytical room with various measurement devices. Our current main interest is to establish a rapid and labor-saving bioassay method for actinides that are likely to cause significant internal exposure. In 2017, five workers from a Japanese nuclear facility accidentally inhaled plutonium compounds; this accident was the first Japanese case associated with medical intervention using decorporation agents (Ca/Zn-DTPA) [1]. QST was involved in the medical treatment and dose assessment, and our bioassay laboratory presented the 239+240Pu and 241Am data by collecting and analyzing ca. 200 urinary samples. To cope with similar situations in the future, we are attempting both the optimization of a conventional method based on alpha spectrometry and the development of a screening method based on mass spectrometry. It is possible to measure U, Pu and Am isotopes by alpha spectrometry; however, mass spectrometry offers a more feasible, less time- consuming method to measure these long-lived actinide isotopes with low specific activity. The combined use of two mass spectrometry devices (SF-ICP-MS and ICP-MS/MS) allows us to rapidly measure multiple actinides (e.g., 234U, 235U, 238U, 237Np, 239Pu, 240Pu) in small-volume urine samples (e.g., 20 ml) and to present the isotope ratios (e.g., 240Pu/239 Pu) for source identification [2]. For fecal samples, microwave-assisted aging and digestion are used to shorten the pretreatment to < 8 h. Our developed techniques have been tested and validated through relevant exercises (e.g., PROCORAD) for the purpose of obtaining future international accreditation., International Conference on Individual Monitoring of Ionising Radiation (IM2022) and Neutron and Ion Dosimetry Symposium (NEUDOS-14)

In case of nuclear accidents, it is important to determine the magnitude of radiation doses received by people living in contaminated territories. Direct measurement of individual external doses using personal dosimeters (PDs) worn by subjects is the most reliable solution for this necessity. However, it is not practical to expect that all returnees to the affected areas wear PDs. Thus, conversion factors from the ambient dose equivalent (ADEs) to the effective dose for various aged individuals must be determined appropriately. Previous studies demonstrated that the ratio of PDs to ADEs at various areas of Fukushima Prefecture mostly existed in the range of 0.6-0.7 [e.g.,1-3]. These studies provided evidence that PD readings would be reasonable estimators for the effective doses of adult subjects at locations where radioactive cesium is widely and uniformly deposited on the ground. In the present study, we experimentally obtained the response of PDs (D-shuttle, Chiyoda Technol., Tokyo, Japan; Dose i, Fuji Electric, Tokyo, Japan) attached to the front of five age-specific anthropometric phantoms (newborn, 1 y, 5y, 10y and adult male) for lateral radiations of 137Cs with various rotational angles. The PD/ADE ratio for the D-shuttle on the five phantoms with rotational irradiation simulating the exposure in Fukushima Prefecture were 0.87, 0.85, 0.83, 0.83 and 0.77, respectively. The ratio for newborns was 11 % higher than that for adult males. This body size dependency can be explained by the PD response to exposure direction. We discussed the results of this study and our field experiments to construct conversion coefficients from the ADE to the effective doses for age-group residents living in affected areas, which will be presented at the conference., International Conference on Individual Monitoring of Ionising Radiation (IM2022) and Neutron and Ion Dosimetry Symposium (NEUDOS-14)

Background: Local hemodynamics are known to play an important role in the development of plaque erosion. Recent studies showed that erosion patients might be treated conservatively without stent implantation. We investigated evolution of hemodynamic parameters on the plaque erosion site in conservatively treated patients. Methods: Computational fluid dynamics (CFD) simulations were performed using the coronary angiogram and optical coherence tomography (OCT) images of non-stent treated erosion patients who had serial OCT studies. Calculated CFD parameters included endothelial shear stress (ESS), ESS gradient (ESSG), and oscillatory shear index (OSI).Results: The CFD parameters at the erosion and non-erosion sites were compared among baseline (n = 23), and 1-month (n = 20) and 12-month (n = 16) follow-ups. The erosion site had higher ESS and ESSG values than the non-erosion sites at baseline (mean ESS: 3.00 vs 1.36 Pa, p < 0.01; mean ESSG: 1.71 vs. 0.65 Pa/mm, p = 0.01), 1-month (mean ESS: 2.89 vs 1.19 Pa, p < 0.01; mean ESSG: 1.71 vs. 0.60 Pa/mm, p < 0.01), and 12-month (mean ESS: 3.26 vs 1.59 Pa, p < 0.01; mean ESSG: 1.87 vs. 0.78 Pa/mm, p < 0.01). OSI was not different between erosion and and non-erosion sites. Conclusions: ESS and ESSG values were higher at the plaque erosion sites compared to non-erosion sites. Elevated ESS and ESSG at the erosion site persisted up to 12 months. These data indicate that a local thrombogenic milieu related to hemodynamic perturbation persists up to 12 months at the plaque erosion sites following conservative treatment.

In 2017, five workers were involved in the internal contamination accident at a nuclear facility of the Japan Atomic Energy Agency in Oarai-town, Ibaraki Prefecture, Japan. They accidentally inhaled plutonium compounds (containing Pu and Am isotopes) and the maximum committed effective dose was estimated as a range of 100−200 mSv [1]. Internal contamination with alpha-particle emitting actinides, such as 239Pu, 240Pu, is likely to bring a large amount of dose to the tissues of persons even if the intake amount is small. Therefore, after this accident, medical intervention using decorporation agents (Ca/Zn-DTPA) to patients was performed for the first time in Japan. This chelation therapy was continued for several weeks or months and ca. 200 urinary samples were collected from the five workers before and after each DTPA administration. To cope with similar situations in the future and provide timely information for prompt decision-making in radiation emergency therapy, we are attempting both the optimization of a conventional method based on alpha spectrometry and the development of a screening method based on mass spectrometry [2]. In terms of mass spectrometric method, to eliminate matrix, polyatomic interferences and tailing effects from U, after LaF 3 /CaF 3 coprecipitation, Pu isotopes were collected after removing U effectively (exhibiting a high decontamination factor of 108 for 238U) using a single chromatographic column packed with 2 mL AG MP-1M anion exchange resin. The Pu isotopes were measured using 242 Pu as a yield tracer with yields of 76±5%. Using ICP-MS/MS with low background, very low method detection limits for 239 Pu, 240 Pu, and 241 Pu of 0.057, 0.126, and 76.8 mBq L -1 , respectively, were obtained for 20 mL of urine sample. These detection limits were comparable to those of SF-ICP-MS with higher sensitivity [2]. In terms of alpha spectrometric method, after decomposing organic matter completely with HNO3 and H2O2 , in order to eliminate matrix and interferences, the combination of the iron hydroxide co-precipitation and the automated separation using the TEVA and DGA resin cartridges was used prior to 48 h counting using alpha spectrometer. This method presented stable and high (~ 80%) yields for Pu, Am, and U, and low method detection limits (< 0.5 mBq using 500 mL urine sample). Subsequently, these alpha and mass spectrometric methods were applied to participate in the intercomparison organized by the Association for the PROmotion of Quality COntrol in RADiotoxicological Analysis (PROCORAD), France, for method validation., International Conference on Individual Monitoring of Ionising Radiation (IM2022) and Neutron and Ion Dosimetry Symposium (NEUDOS-14)

As an alkali earth element, Sr could accumulate in bone tissue. Additionally, the potential beta energies of 90Sr (end point energy 0.54 MeV) and its daughter nuclide 90Y (2.27 MeV; half-life 64 h) are very high. Internal exposure with 90Sr is likely to bring long-term radiation exposure due to its long physical (t1/2 = 28.64 y) and biological half-life. For an adult, the inhalation dose coefficients applied in case of internal intake are higher for 90Sr ((2.4−16) × 10-8 Sv Bq-1) than that for 137Cs ((4.6−39) × 10-9 Sv Bq-1) [1]. It is thus of great importance to timely evaluate the order of magnitude of the dose to the person(s) of concern in order to provide information for decision making in radiation emergency medicine. In case of internal exposure for the public with a large scale, it is also critical to perform rapid screening of persons who require emergency medical care from a large number of potentially exposure people. In terms of radiobioassay, urine is an essential and sensitive material to estimate the internal intake of 90Sr. In the present study, a novel method was developed with emphasis on the chromatographic purification and optimization of collision/reaction gases in ICP-MS/MS for 90Sr determination in small volume of urine. After organic matter decomposition of 10 mL urine, stacked DGA and Sr resin cartridges were used for chromatographic separation and purification of Sr from the urine matrix and other interfering elements. During chromatographic purification and the whole procedure, Sr yields were measured as 94.0±5.4 % (n=3) and 88.4±7.8 % (n=3), respectively. To overcome isobaric/polyatomic interferences further and peaking tailing effect from stable 88Sr with high concentration in urine, different collision/reaction gases (CO2, O2, N2O, NH3, He, and H2) were introduced into the gas cell of an ICP-tandem mass spectrometer (8900, Agilent Technologies, Santa Clara, CA, USA) for parameter optimization to increase the signal intensity of 90Sr and decrease the interfering signal intensities (Figure 1). Spiked urine samples were analyzed to validate the proposed method., 第23回「環境放射能」研究会

It is very important to determine the precise internal thyroid doses of Fukushima residents involved in the 2011 Fukushima nuclear disaster, particularly for small children. This has been challenging due to the lack of direct human measurements to identify 131I, the biggest contributor to the thyroid doses. We previously used a dataset of late whole-body counter (WBC) measurements targeting 134Cs and 137Cs for the thyroid dose estimation in comparison with the intake ratios of 131I to 137Cs (or 134Cs) derived from thyroid and whole-body doses individually obtained from different subject groups, assuming simultaneous acute intake via inhalation. Herein, we applied the same method to the doses of residents in Iwaki city (located south of the Fukushima Daiichi Nuclear Power Plant) with a relatively high activity ratio (131I/137Cs) for the ground deposition density. Our analyses revealed that the intake ratio (131I/137Cs) for the Iwaki residents was 4.2–4.3, which is relatively consistent with the values obtained in other studies (average 3.0–5.0). No regional difference in the intake ratios from other areas was observed, but further studies are required to determine the accurate intake ratio in the early phase of the accident, in particular focusing on the reasonable interpretation of results of the late WBC measurements to evaluate the actual Cs intake.

For the 2019 PROCORAD (Association for the PROmotion of Quality COntrol in RADiotoxicological Analysis) intercomparison campaign for urine actinides analysis, we compared SF-ICP-MS and ICP-MS/MS combined with chromatographic separation using TEVA+UTEVA+DGA resins and alpha spectrometry combined with chromatographic separation using TEVA resin for the measurement of 239Pu. The Pu yields were in the range of 68–93 % (n=20). Both the methods of SF-ICP-MS (2.44±0.05 mBq/sample for 19 ACTA, n=4 and 7.63±0.13 mBq/sample for 19 ACTB, n=4) and ICP-MS/MS (2.45±0.21 mBq/sample for 19 ACTA, n=1 and 7.89±0.54 mBq/sample for 19 ACTB, n=1) presented precise and accurate results that agreed well with the assigned values (2.52±0.26 mBq/sample for 19 ACTA and 7.56±0.39 mBq/sample for 19 ACTB). The method of alpha spectrometry, showing larger uncertainties, also presented comparable results (3.49±1.29 mBq/sample for 19 ACTA, n=1 and 8.05±1.76 mBq/sample for 19 ACTB, n=1). Due to the high sensitivity of SF-ICP-MS and ICP-MS/MS, rapid determination of 239Pu (ca. 10 h) can be achieved in small volume urine sample (20 mL) generally. In contrast, the method of alpha spectrometry generally consumes more sample (e.g. 500 mL) and is more time-consuming. Therefore, it would be more feasible to measure long-lived 239Pu and 240Pu by the methods of SF-ICP-MS and ICP-MS/MS, and short-lived 238Pu by the method of alpha spectrometry for emergency response.

The dose reconstruction of populations potentially affected by the accident at the Fukushima Daiichi Nuclear Power Plant in March 2011 is of great importance. However, it has been difficult to assess thyroid internal doses of Fukushima residents mainly from their intake of 131I due to the lack of direct measurements. Only about 1,300 data of the residents related to 131I have been available, and 1,080 of the data were obtained from the screening campaign that was conducted by the Nuclear Emergency Response Local Headquarter at the end of March 2011 in Kawamata-town, Iwaki-city, and Iitate-village. Here, we reassessed the thyroid doses of the 1,080 subjects aged  15-y-old by using new age-specific conversion factors to determine the 131I thyroid contents from net signals of the devices used, with consideration of the possible uncertainty related to the measurements. The results demonstrated that the thyroid equivalent doses of the subjects were < 30 mSv (excluding outliers). We also demonstrate the dose distributions of each age group from the above three municipalities and those of subjects from Minamisoma-city and Fukushima-city. One of the findings was that the 131I intake was similar among different age groups in each of the three municipalities. This was consistent with the assumption that ingestion was a dominant route of intake rather than inhalation. The range of thyroid doses for Iitate-village were similar to that for Iwaki-city even though the 131I concentration in tap water was much higher in Iitate-village than Iwaki-city. The range of thyroid doses for Minamisoma-city was similar to those for Iitate-village and Iwaki-city, and the range for Fukushima-city was smallest among the five municipalities. Since the major route of intake has remained unclear, this paper presented the plausible upper and lower thyroid doses, between which the actual doses are thought to exist mostly, based on the two intake scenarios: single inhalation and repeated ingestion. Further research is thus necessary to extract useful evidence from the individual evacuation behaviors for improving the present thyroid internal dose assessment.

Internal contamination with alpha-particle emitting actinides, such as 238U, 237Np, 239Pu, 240Pu, is likely to result in high internal exposure risk even if the intake amount is small. To provide valuable information apart from urinary bioassay for internal dose estimation, we developed a simple and rapid method for fecal bioassay to determine ultra-trace U, 237Np, and Pu isotopes in synthetic feces using ICP-MS/MS and alpha spectrometry, respectively. After rapid ashing by microwave muffle furnace and acid digestion by opening and microwave digestions, the sample was separated for analyses by ICP-MS/MS and alpha spectrometry, respectively. Conventional alpha spectrometry was used for the analysis of short-lived 238Pu (t1/2 = 87.74 y) for dose estimation, the ICP-MS/MS was used to obtain the atom ratio of 240Pu/239Pu for source identification. The sensitivities of ICP-MS/MS were improved and compared by introducing different reaction/collision gases to allow us to measure these isotopes with low background signal intensities., 日本放射化学会第65回討論会(2021)

Estimating the internal thyroid dose received by residents involved in the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has been a challenging task because of the shortage of direct human measurements related to the largest contributing radioisotope to the dose, 131I. In a previous dose estimation, we used the results of whole-body counter (WBC) measurements targeting 134Cs and 137Cs, based on the assumption that these radioisotopes were incorporated at the same time as 131I in the early phase of the accident. The main purpose of this study was to clarify whether the trace of the early intake remained in the WBC measurements that were started several months after the accident. In the present work, WBC data of 1,639 persons from Namie town, one of the heavily contaminated municipalities, were analyzed together with their evacuation behavior data. The results demonstrated that the Cs detection rate in the WBC results was several times higher in the late evacuees (who evacuated outside the 20-km radius of the FDNPP at 3:00 p.m. [Japanese Local Time] on 12 March or later) compared to the prompt evacuees (who evacuated before 3:00 p.m. on 12 March). Among the adults, the Cs detection rates (and the 90th percentile values of the 137Cs intake) of the prompt and late evacuees were about 20% (5.4  103 Bq) and 60% (1.6  104 Bq), respectively. Approximately 20% of the individuals analyzed were categorized as late evacuees. These differences in Cs would be caused by exposure to the radioactive plume in the afternoon on 12 March, which was likely to influence the late evacuees. On the other hand, the intake on 15 March when the largest release event occurred was expected to be relatively small for Namie town's residents. In conclusion, the trace of the early intake remained in the WBC measurements, although this would not necessarily be true for all subjects. The results obtained from this study would provide useful information for the reconstruction of the early internal thyroid doses from radioiodine in the future.

Past radiological and nuclear accidents have demonstrated that monitoring a large number of children following a radiological and nuclear emergency can be challenging, in accommodating their needs as well as adapting monitoring protocols and applying age-specific biokinetics to account for various ages and body sizes. This paper presents the derived calibration factors for thyroid monitoring of children of all ages recommended by the International Commission on Radiological Protection using four selected detectors at given times following a short-term(acute) intake of 131I by inhalation. These calibration factors were derived byMonte Carlo simulations using the models of various detectors and pediatric voxel phantoms. A collection of lookup tables is presented in this paper which may be directly used as a quick reference by emergency response personnel or technical experts performing thyroid monitoring and assessment without doing time-consuming calculations.

Technetium-99m-galactosyl human serum albumin (99mTc-GSA) is a molecular imaging agent used for evaluating hepatic function. 99mTc-GSA hepatic scintigraphy examinations were performed in 50 patients from December 2018 to November 2019 at the QST Hospital in Japan. In order to estimate the individual variation in absorbed doses for each patient, a method of internal dose assessment for multiple organs and tissues in 99mTc-GSA scintigraphy was developed using a nine-compartment biokinetic model that took advantage of the existing models. This method is also expected to give a better understanding of metabolic changes along with the disease progress. Transfer rates related to the liver and blood compartments of the biokinetic model were optimized for each examination by comparing the time-activity curves for the liver and heart derived from the model with those clinically observed on individual dynamic images over the trunk region using the gamma camera after intravenous injection of 99mTc-GSA. Simultaneous differential equations describing the activity in each compartment were numerically analyzed using EQUATRAN-G, a commercial software, by that the total amount of disintegrations taken place in each compartment over a period of 2.5 days, which corresponds to nearly 10 physical half-lives of 99mTc, was obtained. Absorbed doses of several organs and tissues were calculated using the internal dose calculation software, IDAC-Dose 2.1. As a result, the calculated average dose per unit administered activity (mGy/MBq) for the liver was the highest (0.058 ± 0.007 mGy/MBq for females and 0.042 ± 0.009 mGy/MBq for males) compared to other organs and tissues, and the average dose for males was lower than that estimated for healthy males in a past study (0.054 mGy/MBq)., 15th International Congress of the International Radiation Protection Association (IRPA15)

Background A recent study reported that the outcome of patients with plaque erosion treated with stenting is poor when the underlying plaque is lipid rich. However, the detailed phenotype of patients with plaque erosion, particularly as related to different age groups, has not been systematically studied. Methods and Results Patients with acute coronary syndromes caused by plaque erosion were selected from 2 data sets. Demographic, clinical, angiographic, and optical coherence tomography findings of the culprit lesion were compared between 5 age groups. Among 579 erosion patients, male sex and current smoking were less frequent, and hypertension, diabetes, and chronic kidney disease were more frequent in older patients. ST‐segment–elevation myocardial infarction was more frequent in younger patients. Percentage of diameter stenosis on angiogram was greater in older patients. The prevalence of lipid‐rich plaque (27.3% in age P P =0.027), and calcification (5.5% in age P Conclusions The demographic, clinical, angiographic, and plaque phenotypes of patients with plaque erosion distinctly vary depending on age. This may affect the clinical outcome in these patients. Registration URL: https://www.clinicaltrials.gov . Unique identifiers: NCT03479723, NCT02041650.

Following a radiological or nuclear emergency, workers, responders and the public may be internally contaminated with radionuclides. Screening, monitoring and assessing any internal contamination and providing necessary medical treatment, especially when a large number of individuals are involved, is challenging. Experience gained and lessons learned from the management of previous incidents would help to identify gaps in knowledge and capabilities on preparedness for and response to radiation emergencies. In this paper, eight large-scale and five workplace radiological and nuclear incidents are reviewed cross 14 technical areas, under the broader topics of emergency preparedness, emergency response and recovery processes. The review findings suggest that 1) new strategies, algorithms and technologies are explored for rapid screening of large populations; 2) exposure assessment and dose estimation in emergency response and dose reconstruction in recovery process are supported by complementary sources of information, including 'citizen science'; 3) surge capacity for monitoring and dose assessment is coordinated through national and international laboratory networks; 4) evidence-based guidelines for medical management and follow-up of internal contamination are urgently needed; 5) mechanisms for international and regional access to medical countermeasures are investigated and implemented; 6) long-term health and medical follow up programs are designed and justified; and 7) capabilities and capacity developed for emergency response are sustained through adequate resource allocation, routine non-emergency use of technical skills in regular exercises, training, and continuous improvement.

Aims Layered plaques represent signs of previous plaque destabilization. A recent study showed that acute coronary syndrome (ACS) patients with layered culprit plaque have more vulnerability at the culprit lesion and systemic inflammation. We aimed to compare the characteristics of non-culprit plaques between patients with or without layered plaque at the culprit lesion. We also evaluated the characteristics of layered non-culprit plaques, irrespective of culprit plaque phenotype. Methods and results We studied ACS patients who had undergone pre-intervention optical coherence tomography (OCT) imaging. The number of non-culprit lesions was evaluated on coronary angiogram and morphological characteristics of plaques were studied by OCT. In 349 patients, 99 (28.4%) had layered culprit plaque. The number of non-culprit plaques in patients with or without layered culprit plaque was similar (3.2 ± 0.8 and 2.8 ± 0.8, P = 0.23). Among 465 non-culprit plaques, 145 from patients with layered culprit plaque showed a higher prevalence of macrophage infiltration (71.0% vs. 60.9%, P = 0.050). When analysed irrespective of culprit plaque phenotype, layered non-culprit plaques showed higher prevalence of lipid (93.3% vs. 86.0%, P = 0.028), thin cap fibroatheroma (29.7% vs. 13.7%, P Conclusion In ACS patients, those with layered phenotype at the culprit lesion demonstrated greater macrophage infiltration at the non-culprit sites. Layered plaque at the non-culprit lesions was associated with more features of plaque vulnerability, particularly when the culprit lesion also had a layered pattern.

Comparison is an important role in the quality control and quality assurance for any measuring system. Due to the future legal regulations regarding radon levels in the air, maintaining the system quality and harmonization of results as well as validation of radon and thoron measuring systems is important. The aim of this work is to validate the degrees of equivalence and measurement precisions of the existing five radon and four thoron measuring systems located in four Asian countries (China, India, Japan and Thailand) through comparison experiment. In this project, comparison experiment was performed in order to derive the ratio between assigned value obtained from one transfer measurement device for radon and one transfer measurement device for thoron belongs to National Institutes for Quantum and Radiological Science and Technology and participants&rsquo, value from their measuring instrument. As a result, the ratio value associated with measurement uncertainty was derived for each activity concentration. Finally, measurement bias and degrees of equivalence between the assigned values and values of measurement quantity from participants&rsquo, measuring instruments were statistically analysed and presented.

The 5th QST International Symposium on Radiation Emergency Monitoring and Medicine in Nuclear Disasterを2021年9月に開催したことの紹介。

One of the most important lessons learned from the Fukushima Daiichi Nuclear Power Plant accident is that direct (in vivo) measurements of thyroid exposure to radioiodine (mainly, 131I) in the affected populations should be initiated in a timely manner. Furthermore, the existing commercial detectors are not necessarily suitable for the measurement of young children, who are especially vulnerable to radiation exposure and therefore important to screen. This paper presents the development of a new thyroid monitor for such measurements and the results from phantom-based experiments. The monitor has two unique probes having multiple high-energy-resolution type Gd3(Al,Ga)5O12(Ce) (GAGG) detectors that can be placed directly on the young subject’s anterior neck. The crystal size of the GAGG detector is 1 cm3, and a probe consisting of a 4 × 1 or 4 × 2 detector array can be selected depending on the subject’s body size. The thickness of the 4 × 1 array probe is 24 mm, which is less than that for a conventional NaI(Tl) survey meter having a crystal 1 inch in diameter and 1 inch long (38 mm). Experimental and computational calibrations of the new monitor using existing and virtual phantoms allowed us to determine the full energy peak efficiency for the 131I thyroid contents of different age groups from 3-mo-old to 10-yr-old and minimum detectable activity (MDA) values under various conditions. As a result, the attainable MDA for subjects age ≤5 years under a normal background level (~0.05 μSv h-1) was found to be ~30 Bq, which was low enough to identify children with thyroid-equivalent doses over 10 mSv up to about 25 days after the 131I intake. Our new monitor would be useful in direct thyroid measurements for vulnerable young children following a large nuclear accident.

International audience; Past radiological and nuclear accidents have demonstrated that monitoring a large number of children following a radiological and nuclear emergency can be challenging, in accommodating their needs as well as adapting monitoring protocols and applying age-specific biokinetics to account for various ages and body sizes. This paper presents the derived calibration factors for thyroid monitoring of children of all ages recommended by the International Commission on Radiological Protection using four selected detectors at given times following a short-Term (acute) intake of 131I by inhalation. These calibration factors were derived by Monte Carlo simulations using the models of various detectors and pediatric voxel phantoms. A collection of lookup tables is presented in this paper which may be directly used as a quick reference by emergency response personnel or technical experts performing thyroid monitoring and assessment without doing time-consuming calculations. © Lippincott Williams and Wilkins.

Internal contamination with alpha-particle emitting actinides, such as 237Np, 239Pu, 240Pu, is likely to bring a large amount of dose to the tissues of persons even if the intake amount is small. To provide timely information for prompt decision-making in radiation emergency therapy, we developed a simple and rapid method for urinary bioassay to determine ultra-trace 237Np and Pu isotopes using SF-ICP-MS and ICP-MS/MS. To avoid polyatomic interferences and tailing effects from U, 237Np and Pu isotopes were collected after removing U effectively using a simple single chromatographic column packed with 2 mL AG MP-1M anion exchange resin, exhibiting a high decontamination factor of 108 for 238U. The overall chemical fractionation between 237Np and 242Pu for the whole analytical procedure was 0.974 ± 0.064 (k=2), allowing us to measure 237Np and Pu isotopes using 242Pu as a yield tracer with yields of 76±5%. Using ICP-MS/MS with low background provided the method detection limits for 237Np, 239Pu, 240Pu, and 241Pu of 0.025, 0.025, 0.015, and 0.020 fg mL-1, respectively, for 20 mL of urine sample. Those were comparable to detection limits of SF-ICP-MS with high sensitivity. Subsequently, three urine reference materials with Pu spike, provided by the Association for the PROmotion of Quality COntrol in RADiotoxicological Analysis (PROCORAD), France, were analyzed by the developed method and the conventional alpha spectrometry technique for validation. Finally, the developed method was successfully employed to measure the contamination level of 237Np, 239Pu, 240Pu, and 241Pu in urine samples collected during decorporation therapy using DTPA, after a Pu inhalation exposure accident in Japan. The high throughput (9 h for 12 samples), simplicity, low cost, and high sensitivity of the method will allow greater numbers of related laboratories to be involved in screening activities for unexpected actinide exposure, such as in the case of a large scale radiological disaster.

The experiences of the Chernobyl and Fukushima nuclear accidents showed that dosimetry was the essential tool in the emergency situation for decision making processes, such as evacuation and application of protective measures. However, at the consequent post-accidental phases, it was crucial also for medical health surveillance and in further adaptation to changed conditions with regards to radiation protection of the affected populations. This review provides an analysis of the experiences related to the role of dosimetry (dose measurements, assessment and reconstruction) regarding health preventive measures in the post-accidental periods on the examples of the major past nuclear accidents such as Chernobyl and Fukushima. Recommendations derived from the review are called to improve individual dose assessment in case of a radiological accident/incident and should be considered in advance as guidelines to follow for having better information. They are given as conclusions.

The Asian Radiation Dosimetry Group (ARADOS) was established in 2015 with the aim of promoting collaborations among Asian countries on relevant activities in the field of radiation dosimetry. Since then, annual meetings have been organized by the Republic of Korea, China and Japan in order to share information on the researches done in each country. In past annual meetings, members have discussed the missions and structure of ARADOS, and several collaborative projects were also launched by working groups of ARADOS. This paper introduces an outline of ARADOS and discuss its recent activities.

FASTSCAN (Canberra, Meriden, CT, USA), a standing-type whole-body counter with upper and lower NaI(Tl) detectors, has been mostly used to determine local residents’ level of internal contamination with 134/137Cs following the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster in 2011. In the present study, we performed Monte-Carlo simulations with age-specific mathematical human phantoms to investigate the counting efficiencies of the FASTSCAN counter for 131I thyroid measurements. As a result, although the lower detector had low sensitivity for 131I in the thyroids of the adult and 15 y phantoms as well as the 10 y phantom standing on a 30-cm-high stool, the response of this detector may be used as an indicator of surface contamination overlooked on a subject. The total counting efficiency investigated in this study was 0.017–0.018 (cps/Bq) among all age groups. Based on this sensitivity, the determination level for thyroid activity could be calculated to be ~300 Bq under the slightly elevated background radiation level observed after the FDNPP disaster.

A new thyroid monitor using multiple high energy resolution Gd3(Al,Ga)5O12(Ce) (HR-GAGG) detectors with each crystal size of one cubic centimeter has been developed, in particular with an intention of measuring small children (including infants) for their internal thyroid exposure from radioiodine following a nuclear accident. The small-sized HR-GAGG detectors allowed to be placed around the human neck at the close distance to increase the geometrical efficiency for 131I localized in the thyroid. An arrangement of eight HR-GAGG detectors surrounding the neck was tested using age-specific phantoms in each of which a thyroid-shaped container filled with standard 131I solution was installed, demonstrating that the minimum detectable activity (MDA) of the new monitor reached 20–30 Bq with a counting time of 180 sec, which was about 10 times lower than that of a conventional NaI(Tl) survey meter (with a crystal size of 1 inch in diameter and 1 inch in thickness) commonly used for measuring air dose rates.

Comparison is an important role in the quality control and quality assurance for any measuring system. Due to the future legal regulations regarding radon levels in the air, maintaining the system quality and harmonization of results as well as validation of radon and thoron measuring systems is important. The aim of this work is to validate the degrees of equivalence and measurement precisions of the existing five radon and four thoron measuring systems located in four Asian countries (China, India, Japan and Thailand) through comparison experiment. In this project, comparison experiment was performed in order to derive the ratio between assigned value obtained from one transfer measurement device for radon and one transfer measurement device for thoron belongs to National Institutes for Quantum and Radiological Science and Technology and participants’ value from their measuring instrument. As a result, the ratio value associated with measurement uncertainty was derived for each activity concentration. Finally, measurement bias and degrees of equivalence between the assigned values and values of measurement quantity from participants’ measuring instruments were statistically analysed and presented.

To evaluate the effectiveness of sodium bicarbonate (SB) in removing uranium and protecting animals from uranium toxicity, we intramuscularly administered 1 mg/kg of uranyl nitrate to 8-wk-old male SD rats, and 20 min after administration of uranyl nitrate, the animals were given a single oral administration of SB at 0.1, 0.3 or 1 g/kg. The SB treatment at a dose of 0.3 g/kg or more raised the pH of the rats' urine until 4 h after treatment, and it significantly reduced the uranium amounts in the kidneys at 1 day after treatment. In another experiment, rats were intramuscularly administered 1 mg/kg of uranyl nitrate, and 20 min later, the animals were treated with sodium bicarbonate (0.1 or 1 g/kg). The rats were autopsied at 1, 3 and 7 days after uranium treatment. High-dose SB resulted in a significant increase in urinary uranium excretion in the first 24 h and a reduction of uranium deposition in the kidneys and femurs, and it also significantly suppressed uranium-induced renal toxicity, as shown by both histopathology and clinical chemistry at 3 days after uranium treatment. Low-dose SB did not show such marked effects. Our findings demonstrated that the uranium decorporation effect of sodium bicarbonate was observed at the dosage showing urine alkalinization in rats and that decorporation effect of sodium bicarbonate might be beneficial if it is administered immediately after incorporation of soluble uranium.

OBJECTIVE To determine if prediabetes is associated with atherosclerosis of coronary arteries, we evaluated the degree of coronary atherosclerosis in nondiabetic, prediabetic, and diabetic patients by using coronary angioscopy to identify plaque vulnerability based on yellow color intensity. RESEARCH DESIGN AND METHODS Sixty-seven patients with coronary artery disease (CAD) underwent angioscopic observation of multiple main-trunk coronary arteries. According to the American Diabetes Association guidelines, patients were divided into nondiabetic (n = 16), prediabetic (n = 28), and diabetic (n = 23) groups. Plaque color grade was defined as 1 (light yellow), 2 (yellow), or 3 (intense yellow) based on angioscopic findings. The number of yellow plaques (NYPs) per vessel and maximum yellow grade (MYG) were compared among the groups. RESULTS Mean NYP and MYG differed significantly between the groups (P = 0.01 and P = 0.047, respectively). These indexes were higher in prediabetic than in nondiabetic patients (P = 0.02 and P = 0.04, respectively), but similar in prediabetic and diabetic patients (P = 0.44 and P = 0.21, respectively). Diabetes and prediabetes were independent predictors of multiple yellow plaques (NYPs ≥2) in multivariate logistic regression analysis (odds ratio [OR] 10.8 [95% CI 2.09–55.6], P = 0.005; and OR 4.13 [95% CI 1.01–17.0], P = 0.049, respectively). CONCLUSIONS Coronary atherosclerosis and plaque vulnerability were more advanced in prediabetic than in nondiabetic patients and comparable between prediabetic and diabetic patients. Slight or mild disorders in glucose metabolism, such as prediabetes, could be a risk factor for CAD, as is diabetes itself.

The aim of this study is to propose action levels for chelation therapy in the case of inhalation of plutonium compounds using nose swabs. The relationship between the activity found in the nose swabs and early faecal excretion was investigated using actual cases at JAEA-NFCEL. The ratio was found to be in log-normal distribution. The action levels based on the activity of nose swab corresponding to 10 ALI (=200 mSv) are determined for the facilities at JAEA-NFCEL by using the relationship and specific information such as isotopic ratio and physicochemical characteristics of plutonium compounds.