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Seven emergency nuclear workers, who had internal exposure due to an intake of radionuclides, mainly I-131, during the emergency response operation in March 2011, after the accident at the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP), visited the National Institute of Radiological Sciences (NIRS) outpatient clinic for medical evaluation. They were followed up after their first visit for 10 years. The estimated committed equivalent doses to the thyroid were distributed between 3.2 to 1.2 × 10 Sv. This group thought to be received highest exposure at the accident. None of the workers had symptoms related to abnormal thyroid function. The examinations, including thyroid function tests and ultrasound, detected no abnormalities related to radiation exposure. However, there is a need for continuous monitoring of their thyroid status for longer periods in the future.

Background Diagnostic strategies depend on non-standardized workup, and the causes of myocardial infarction with non-obstructive coronary arteries remain unclear for some patients. Intracoronary imaging is recommended for detecting the missed causes by coronary angiography. Myocardial infarction with non-obstructive coronary arteries is a heterogeneous entity; a meta-analysis of myocardial infarction with non-obstructive coronary artery studies demonstrated that all-cause mortality rate at 1 year is 4.7%, and its prognosis is not so favourable. Case summary A 62-year-old man without remarkable medical history complained of acute chest pain at rest, which resolved at his arrival. Although echocardiography and electrocardiogram exhibited normal findings, the concentration of high-sensitive cardiac troponin T increased up to 0.384 from 0.04 ng/mL. Coronary angiography was performed, and mild stenosis of the proximal right coronary artery was detected. He was discharged without catheter intervention and medications as he reported no symptoms. He returned 8 days later because of inferoposterior ST-segment elevation myocardial infarction with ventricular fibrillation. Emergent coronary angiography showed that the mild stenosis of the proximal right coronary artery had progressed to total occlusion. Optical coherence tomography after thrombectomy revealed rupture of the thin-cap fibroatheroma and protruding thrombus. Discussion Patients presenting with myocardial infarction with non-obstructive coronary arteries and plaque disruption and/or thrombus detected by optical coherence tomography do not show normal coronaries on coronary angiography. Aggressive investigation into plaque disruption using intracoronary imaging is recommended even if coronary angiography demonstrates mild stenosis to prevent a fatal attack for suspicious cases of myocardial infarction with non-obstructive coronary arteries.

Optical coherence tomography (OCT) has been widely adopted in research on coronary atherosclerosis and adopted clinically to optimize percutaneous coronary intervention. In this Review, Jang and colleagues summarize this rapidly progressing field, with the aim of standardizing the use of OCT in coronary atherosclerosis.Since optical coherence tomography (OCT) was first performed in humans two decades ago, this imaging modality has been widely adopted in research on coronary atherosclerosis and adopted clinically for the optimization of percutaneous coronary intervention. In the past 10 years, substantial advances have been made in the understanding of in vivo vascular biology using OCT. Identification by OCT of culprit plaque pathology could potentially lead to a major shift in the management of patients with acute coronary syndromes. Detection by OCT of healed coronary plaque has been important in our understanding of the mechanisms involved in plaque destabilization and healing with the rapid progression of atherosclerosis. Accurate detection by OCT of sequelae from percutaneous coronary interventions that might be missed by angiography could improve clinical outcomes. In addition, OCT has become an essential diagnostic modality for myocardial infarction with non-obstructive coronary arteries. Insight into neoatherosclerosis from OCT could improve our understanding of the mechanisms of very late stent thrombosis. The appropriate use of OCT depends on accurate interpretation and understanding of the clinical significance of OCT findings. In this Review, we summarize the state of the art in cardiac OCT and facilitate the uniform use of this modality in coronary atherosclerosis. Contributions have been made by clinicians and investigators worldwide with extensive experience in OCT, with the aim that this document will serve as a standard reference for future research and clinical application.

—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.

Background: South Asians, and Indians in particular, are known to have a higher incidence of premature atherosclerosis and acute coronary syndromes (ACS) with worse clinical outcomes, compared to populations with different ethnic backgrounds. However, the underlying pathobiology accounting for these differences has not been fully elucidated. Methods: ACS patients who had culprit lesion optical coherence tomography (OCT) imaging were enrolled. Culprit plaque characteristics were evaluated using OCT. Results: Among 1315 patients, 100 were South Asian, 1009 were East Asian, and 206 were White. South Asian patients were younger (South Asians vs. East Asians vs. Whites: 51.6 ± 13.4 vs. 65.4 ± 11.9 vs. 62.7 ± 11.7; p < 0.001) and more frequently presented with ST-segment elevation myocardial infarction (STEMI) (77.0% vs. 56.4% vs. 35.4%; p < 0.001). On OCT analysis after propensity group matching, plaque erosion was more frequent (57.0% vs. 38.0% vs. 50.0%; p = 0.003), the lipid index was significantly greater (2281.6 [1570.8–3160.6] vs. 1624.3 [940.9–2352.4] vs. 1303.8 [1090.0–1757.7]; p < 0.001), and the prevalence of layered plaque was significantly higher in the South Asian group than in the other two groups (52.0% vs. 30.0% vs. 34.0%; p = 0.003). Conclusions: Compared to East Asians and Whites, South Asians with ACS were younger and more frequently presented with STEMI. Plaque erosion was the predominant pathology for ACS in South Asians and their culprit lesions had more features of plaque vulnerability. Clinical Trial Registration: http://www.clinicaltrials.gov, NCT03479723

The mechanisms behind poorer cardiac outcomes in underweight patients with acute coronary syndrome (ACS) are not understood and features of coronary culprit lesions in underweight ACS patients have not been fully examined. A total of 1,683 patients with ACS were divided into 4 groups according to body mass index (BMI):18.5 (n = 73), 18.5 to 24.9 (n = 995), 25 to 29.9 (n = 488), and ≥30 (n = 117). Angiography and optical coherence tomography (OCT) images were analyzed for 1,428 of these patients who had primary percutaneous coronary intervention (PCI) and 838 who had primary PCI with OCT guidance, respectively. Diabetes (p0.001), hypertension (p0.001), and dyslipidemia (p0.001) were less prevalent in BMI18.5. Statin prescription at discharge was less frequent in the BMI18.5 group (p0.001). Quantitative coronary angiography analyses revealed smaller reference vessel (p = 0.001) and minimum lumen diameters after PCI (p = 0.019) and OCT revealed longer lipidic plaque length (p = 0.029) in the BMI18.5 group. Kaplan-Meier analyses revealed higher rates of cardiac mortality (p0.001) and major bleeding (p = 0.034) during the 2-year follow-up in the BMI18.5 group. After adjusting for traditional cardiovascular risk factors, BMI18.5 independently predicted 2-year cardiac mortality (hazard ratio 1.917 [95% confidence interval [1.082 to 3.397], p = 0.026). In conclusion, being underweight contributed to poorer cardiac outcomes in established ACS population. Smaller minimum lumen diameter after PCI and further progressed atherosclerosis at the culprit lesions despite their lower prevalence of comorbid metabolic risk factors may be related partly to poorer cardiac outcomes.

The development of optical coherence tomography (OCT) has revolutionized our understanding of coronary artery disease. In vivo OCT research has paralleled with advances in computational fluid dynamics, providing additional insights in the various hemodynamic factors influencing plaque growth and stability. Recent OCT studies introduced a new concept of plaque healing in relation to clinical presentation. In addition to known mechanisms of acute coronary syndromes such as plaque rupture and plaque erosion, a new classification of calcified plaque was recently reported. This review will focus on important new insights that OCT has provided in recent years into coronary plaque development, progression, and destabilization, with a focus on the role of local hemodynamics and endothelial shear stress, the layered plaque (signature of previous subclinical plaque destabilization and healing), and the calcified culprit plaque.

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.

Objectives This study sought to identify morphological predictors of rapid plaque progression. Background Two patterns of plaque progression have been described: slow linear progression an...

Organization of platelet-rich thrombus at the site of plaque disruption may contribute to rapid progression of atherosclerosis. This study was conducted to investigate if potent platelet inhibition therapy in patients with acute coronary syndromes (ACS) mitigates plaque progression. Patients enrolled in the EROSION study who presented with ACS caused by plaque erosion and underwent serial imaging of the culprit lesion by optical coherence tomography at baseline, 1 month, and 1 year were included. Among 49 patients, 32 (65.3%) patients were treated with glycoprotein IIb/IIIa inhibitor (GPI) in addition to aspirin and ticagrelor. The increase in area stenosis from baseline to 1-year follow-up was significantly smaller in patients treated with GPI, compared to those without GPI therapy (4.8% [− 1.6 to 10.9] vs. 9.6% [4.0 to 21.3], p = 0.031). The cohort was divided into 2 groups based on culprit lesion phenotype at 1 year: Group A, new layer formation at 1-year that was not present at baseline (n = 18); Group B, no new layer formation (n = 31). A new layer was less frequently found at 1 year in patients treated with GPI than in those without GPI (25.0% vs. 58.8%, p = 0.019). Group A, compared to Group B, was associated with a greater increase in area stenosis (19.0 ± 16.4% vs. 3.7 ± 7.1%; p

Background: Despite the significant decline in cardiovascular mortality in women over the past several decades, sex differences in the underlying pathology of acute coronary syndromes remain poorly understood. Previous postmortem studies have demonstrated sex differences in coronary plaque morphology with a higher prevalence of plaque erosion in young women and more plaque rupture in older women after menopause, whereas men showed no increase in prevalence of plaque rupture with age. However, in vivo data are limited. Methods: This study included patients who presented with acute coronary syndrome and underwent preintervention optical coherence tomography imaging of the culprit lesion. The culprit plaque was categorized as plaque rupture, plaque erosion or culprit plaque with calcification, and stratified by age. Features of plaque vulnerability at culprit lesion were also analyzed. Results: In 1368 patients (women=286), women and men had a similar distribution of culprit plaque morphology (plaque rupture versus plaque erosion). However, significant sex differences were found in the underlying mechanisms of acute coronary syndrome among different age groups: women showed a significant ascending trend with age in plaque rupture ( P P P =0.005), and microstructures including macrophages, cholesterol crystals, and calcification ( P =0.026). No trend was observed in men. Conclusions: Age related sex differences in culprit plaque morphology and vulnerability were identified in patients with acute coronary syndrome: prevalence of plaque rupture and vulnerability increased with age in women but not in men. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01110538 and NCT03479723.

The authors’ previous study suggested that a simple standing-type whole-body counter called FASTSCAN (Canberra, Meriden, CT, USA), widely installed throughout Japan after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in March 2011, could be used for thyroid measurements in internal dose assessment after a future radiological incident accompanied by the release of 131I into the environment. The present study performed Monte-Carlo simulations using a computational human phantom with several patterns of body surface contamination and used the results to formulate a method for probabilistic analyses of 131I thyroid activity in persons with surface contamination. The major advantage of this method is that the upper limit of the thyroid activity can be determined from the relative frequency distribution without identifying where body surface contamination remains. Therefore, this method is especially effective for use in the early phase of a radiological incident when time and resources are limited, making it difficult to physically remove all body surface contamination for the purpose of gaining more accurate population-wide thyroid screening measurements. As a case study of the FDNPP accident, the proposed method was applied to the results of in vivo measurements for a male subject with body surface contamination. In comparing the probabilistic analyses before and after removal of the subject’s contaminated work clothes, the uncertainty of the relative frequency distribution of 131I thyroid activity was reduced by their removal. Therefore, in terms of accurate estimates and avoidance of radiation exposure from their contaminated clothes, efforts to remove body surface contamination still should be made as much as possible in the chaotic situation of the early phase of a radiological incident.

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.

Statin therapy reduces low-density lipoprotein cholesterol (LDL-C), inflammation, and atherosclerotic cardiovascular disease. We investigated the association between LDL-C and statin therapy on the prevalence of plaque rupture (PR). Patients with acute coronary syndromes who underwent optical coherence tomography imaging of the culprit lesion were divided into 4 groups based on LDL-C level and statin use (Group 1: LDL-C ≤ 100 without statin; Group 2; LDL-C ≤ 100 with statin; Group 3: LDL-C > 100 with statin; Group 4: LDL-C > 100 without statin), and the prevalence of PR was compared between the groups. Among 896 patients, PR was diagnosed in 444 (49.6%) patients. The prevalence of PR was significantly different among the 4 groups (p = 0.007): it was highest in the high LDL-C without statin group and lowest in the low LDL-C without statin group (53.9% and 39.2%, respectively). Compared with the high LDL-C without statin group, the low LDL-C without statin and low LDL-C with statin groups had a significantly lower prevalence of PR (p = 0.001, p = 0.040, respectively), and the low LDL-C with statin group had a significantly higher prevalence of calcification (p = 0.037). The patients with naturally low LDL-C have the lowest risk of PR. The patients with low LDL-C achieved by statin therapy had a higher prevalence of calcification. When LDL-C level is elevated, early and aggressive treatment with statin may help to prevent PR by stabilizing plaques through calcification.

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.

Antiplatelet agents and statin therapies are widely used in patients with known cardiovascular disease. Plaque rupture (PR) and plaque erosion (PE) are the most frequent underlying mechanisms of acute coronary syndromes (ACS). The conditions and medications that are associated with ST-segment elevation myocardial infarction (STEMI) following PR or PE have not been systematically studied. A total of 838 ACS patients (494 with STEMI, 344 with NSTE-ACS) who were diagnosed with PR or PE by optical coherence tomography were included. The patients were categorized into two groups based on underlying pathology, and the baseline characteristics and culprit plaque morphology associated with STEMI were investigated within each group. Among 838 patients, 467 (55.7%) had PR, and 371 (44.3%) were diagnosed with PE. Among patients with PR, older age, hyperlipidemia, no antiplatelet therapy, higher level of low-density lipoprotein cholesterol, and greater lipid burden and macrophage infiltration were associated with increased probability of STEMI. Among patients with PE, no dual antiplatelet therapy and no statin therapy were associated with increased probability of STEMI. The incidence of STEMI caused by PR was significantly lower on antiplatelet therapy (P

Background Previous pathology studies demonstrated that thin-cap fibroatheroma (TCFA) is localized in specific segments of the epicardial coronary arteries. A detailed description of in vivo coronary plaques of various phenotypes has not been reported. Objectives We performed a comprehensive analysis on the distribution of coronary plaques with different phenotypes from our 3-vessel optical coherence tomography (OCT) database. Methods OCT images of all 3 coronary arteries in 131 patients were analyzed every 1 mm to assess plaque phenotype and features of vulnerability. In addition, plaques were divided into tertiles according to percent area stenosis (%AS). Results Among 534 plaques identified in 393 coronary arteries, 27.0% were fibrous plaques, 13.3% fibrocalcific plaques, 40.8% thick-cap fibroatheromas, and 18.9% thin-cap fibroatheromas (TCFA). TCFAs showed clustering in the proximal segment, particularly in the left anterior descending (LAD) artery. On the other hand, fibrous plaques were relatively evenly distributed throughout the entire length of the coronary arteries. In patients with acute coronary syndromes (ACS), TCFAs showed stronger proximal clustering in the LAD, two clustering peaks in the right coronary artery, and one clustering peak in the circumflex artery. The pattern of TCFA distribution was less obvious in non-ACS patients. The prevalence of TCFA was higher in the highest %AS tertile, compared to the lowest %AS tertile (30% vs. 9%, p Conclusions The present 3-vessel OCT study demonstrated that TCFAs cluster at specific locations in the epicardial coronary arteries, especially in ACS patients. TCFA was more prevalent in segments with tight stenosis.

Ethnic differences in the pathobiology of acute coronary syndromes (ACS) have not been systematically studied. We compared the underlying mechanisms of ACS between Asians and Whites. ACS patients with the culprit lesion imaged by optical coherence tomography were included. Patients were stratified into ST-elevation myocardial infarction (STEMI) and non-ST-elevation-ACS (NSTE-ACS), and baseline characteristics, underlying mechanisms of ACS, and culprit plaque characteristics were compared between Asians and Whites. Of 1,225 patients, 1,019 were Asian (567 STEMI and 452 NSTE-ACS) and 206 were White (71 STEMI and 135 NSTE-ACS). Asians had more diabetes and hypertension among STEMI patients; among NSTE-ACS patients, Asians had higher prevalence of diabetes and renal insufficiency, and lower prevalence of hyperlipidemia. There were no differences in the incidence of plaque rupture, plaque erosion and calcified plaque between Asians and Whites with STEMI (61.2%, 28.6%, 10.2% vs 46.5%, 38.0%, 15.5%, respectively, p = 0.055). Among NSTE-ACS patients, there was a significant difference between Asians and Whites (40.5%, 47.6%, 11.9% vs 27.4%, 48.9%, 23.7%, respectively, p = 0.001). After adjustment for clinical confounders, the risk of plaque rupture (p = 0.713), plaque erosion (p = 0.636), and calcified plaque (p = 0.986) was similar between the groups with STEMI. In NSTE-ACS patients, the only difference was an increased risk of calcified plaque in Whites (odds ratio: 2.125, 95% confidence interval: 1.213 to 3.723, p = 0.008). In conclusion, after adjustment for clinical confounders, Asian and White patients presenting with STEMI and NSTE-ACS showed similar underlying mechanisms of ACS, except for a higher risk of calcified plaque in Whites with NSTE-ACS.

As the degree of luminal narrowing increases, shear stress increases, and high shear stress is known to activate platelets. However, the relationship between the degree of luminal narrowing and the composition of thrombus in patients with plaque erosion has not been studied. A total of 148 patients with plaque erosion and thrombus detected by optical coherence tomography were divided into tertiles based on the minimum lumen area (MLA) at the culprit lesion. Thrombus was categorized as platelet-rich or fibrin-rich. Among 148 patients, 50 (34%) were in the mild stenosis group, 49 (33%) were in the moderate stenosis group, and 49 (33%) were in the severe stenosis group. The composition of thrombus was significantly different among the 3 groups (prevalence of platelet-rich thrombus was 60% in the mild stenosis group; 78% in the moderate stenosis group; and 84% in the severe stenosis group; P = 0.021). The pattern of fibrin-rich thrombus showed the opposite: 40%, 22%, and 16%, respectively. In the multivariate analysis, current smoking was independently associated with fibrin-rich thrombus (odds ratio [OR] 2.364 [95% CI 1.004–5.567], P = 0.049). This study demonstrated that platelet-rich thrombus was the predominant type of thrombus in plaque erosion. The prevalence of fibrin-rich thrombus was highest in the mild stenosis group.

Recent studies have shown that healed plaque at the culprit lesion detected by optical coherence tomography (OCT) is a sign of pan-vascular vulnerability and advanced atherosclerosis. However, the clinical significance of healed plaque is unknown. A total of 265 patients who had OCT imaging of a culprit vessel and 2-year clinical follow-up data were included. Patients were stratified based on the presence or absence of a layered plaque phenotype, defined as layers of different optical density by OCT at either culprit or non-culprit lesions. The association between layered plaque and major adverse cardiac events (MACE), defined as cardiac death, acute coronary syndromes (ACS), or revascularization, was studied. Among 265 patients, 96 (36.2%) had the layered plaque phenotype. Layered plaque was more frequently observed in stable angina pectoris patients than in ACS patients (57.8%vs. 25.1%, p

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 March 12, 2011 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.

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.

近年、α線放出核種を使用した標的アイソトープ治療に関する研究が多く実施されており、将来的には同一の医療施設において数種類のα線放出核種（223Ra, 211At, 225Ac等）が使用されることが予想される。そこで、本研究では医療現場における放射線管理への実用化を目指し、核種弁別可能な可搬型α線スペクトルサーベイメータを開発している。本発表では、コリメータによるエネルギー分解能の向上について検討した結果を報告する。, 第３回日本放射線安全管理学会・日本保健物理学会合同大会

Introduction: Despite the significant decline in cardiovascular mortality in women over the past few decades, sex differences in the underlying mechanisms remain poorly understood. Previous postmortem studies have demonstrated differences between men and women in coronary plaque characteristics with a higher prevalence of plaque erosion in young women, but more plaque rupture (PR) in older women after menopause. However, in vivo data are limited. Methods: This study included 1368 patients with acute coronary syndrome undergoing pre-intervention optical coherence tomography (OCT) imaging from a multicenter international registry. The culprit plaque was categorized as plaque rupture, plaque erosion or calcified plaque, and stratified by age. Plaque microstructures at culprit lesion were also analyzed. Results: Sex differences were found in the underlying mechanisms of the culprit lesion: In women a significant ascending trend with age (PP Conclusions: An increasing trend in the prevalence of PR and plaque vulnerability with age was observed only in women but not in men.

肝予備能を評価する放射性医薬品として、正常な肝細胞に存在するアシアロ糖タンパクと特異的に結合する99mTc-GSAが使用されている。本研究では、2018年12月から2019年11月までの期間にQST病院において99mTc-GSAによる肝受容体シンチグラフィ検査の適用となった50名の肝腫瘍患者を対象として、内部被ばく線量を評価することを目的とした。静脈注射によって投与された99mTc-GSAの尿中及び便中への排泄に至る経路を考慮したコンパートメントモデルを構築し、過去の文献を参照して移行係数を決定した。ただし、肝臓及び血液に関連する移行係数は患者ごとの肝予備能に依存するため、ガンマカメラで撮像した99mTc-GSA投与後のダイナミック画像から得られる肝臓及び心臓における計数率の時間変化を再現するように最適化した。各コンパートメントにおける放射能の時間変化を連立微分方程式で記述し、2.5日間（99mTcの10半減期に相当）にわたる総崩壊数を数値解析ソフトウェア（EQUATRAN-G）で計算した。各臓器・組織における吸収線量を内部被ばく線量評価ソフトウェア（IDAC-Dose 2.1）で計算した結果、投与量あたりの平均線量は肝臓で最も高く、0.058±0.007 mGy/MBq（女性20例）及び0.042±0.009 mGy/MBq（男性35例）であった。特に、男性について評価された結果は、過去に男性健常人を対象として評価された肝臓の線量（0.054 mGy/MBq）よりも低かった。, 第2回標的アイソトープ治療線量評価研究会

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)

Organization of platelet-rich thrombus at the site of plaque disruption may contribute to rapid progression of atherosclerosis. This study was conducted to investigate if potent platelet inhibition therapy in patients with acute coronary syndromes (ACS) mitigates plaque progression. Patients enrolled in the EROSION study who presented with ACS caused by plaque erosion and underwent serial imaging of the culprit lesion by optical coherence tomography at baseline, 1 month, and 1 year were included. Among 49 patients, 32 (65.3%) patients were treated with glycoprotein IIb/IIIa inhibitor (GPI) in addition to aspirin and ticagrelor. The increase in area stenosis from baseline to 1-year follow-up was significantly smaller in patients treated with GPI, compared to those without GPI therapy (4.8% [- 1.6 to 10.9] vs. 9.6% [4.0 to 21.3], p = 0.031). The cohort was divided into 2 groups based on culprit lesion phenotype at 1 year: Group A, new layer formation at 1-year that was not present at baseline (n = 18); Group B, no new layer formation (n = 31). A new layer was less frequently found at 1 year in patients treated with GPI than in those without GPI (25.0% vs. 58.8%, p = 0.019). Group A, compared to Group B, was associated with a greater increase in area stenosis (19.0 ± 16.4% vs. 3.7 ± 7.1%; p 0.001). Potent platelet inhibition with GPI in patients with ACS caused by plaque erosion was associated with lower incidence of new layer formation and less plaque progression.