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Although several cases of radiation-induced skin injury (RSI) have been reported in association with neurointerventional procedures such as endovascular embolization for cerebral aneurysm, cerebral arteriovenous malformation, and dural arteriovenous fistula, in most cases the absorbed doses are not measured directly; therefore, we built the first direct measurement system that enables the ideal dosimetry for entrance skin dose (ESD) during neurointerventional procedures to be easily determined. This system was then applied to a 55-year-old man who underwent two transvenous embolizations with a 2-month interval, for a right cavernous sinus dural arteriovenous fistula, to establish the efficacy of precise mapping of ESDs. Throughout the procedures, the patient wore a fitted dosimetry cap that contained 60 radiophotoluminescence glass dosimeter (RPLGD) chips. After the first procedure, temporary epilation occurred in the occipital region. Precise mapping of ESDs revealed that this region was exposed to 4.2 Gy. In the first procedure, the X-ray tube was generally positioned straight for an optimal posterior–anterior view; however, in the second procedure we intermittently used the second-best position to prevent further RSI. In this position, the maximum ESD was 1.0 Gy in the right posterior-temporal region and the epilation site was exposed to ≤0.7 Gy. Thus, the patient did not develop any further epilation. We conclude that direct dosimetry using multiple RPLGDs can accurately reveal the maximum ESD and that precise information regarding ESD can prevent further RSIs from subsequent procedures.

Individual external doses for the first 4 months after the Fukushima accident have been estimated by the ‘Basic Survey’ of the Fukushima Health Management Survey. On the other hand, the UNSCEAR 2013 report presented the first-year effective dose due to external radiation for each municipality in nonevacuated areas of Fukushima Prefecture. In this study, the doses estimated by the Basic Survey were averaged for each of three age groups (infants, 0–5 y; children, 6–15 y; and adults, >16 y), in accordance with the categories adopted by the UNSCEAR report. The average dose ratios (infants/adults and children/adults) obtained from the Basic Survey were 1.08 and 1.06 for nonevacuated areas, respectively. These were smaller than the estimation by the UNSCEAR report (1.7 and 1.4, respectively). Three factors (body size factor, location factor and occupancy factor) were discussed and the location and occupancy factors were likely to be reasons for the difference.

Following the Fukushima Daiichi Nuclear Power Plant accident, a survey for estimating individual external doses for the first 4 months after the accident was started, and it remains ongoing. Since the authors’ previous paper, 44 605 new dose estimates have been made. The new dose estimates increase the number of dose estimates to 465 999 and are reported in this note. Since the previous paper, most of the recently collected responses have been gotten through public relations activities to encourage responses across the prefecture. Thus, recent respondents might be biased (‘selection bias’). Also, the dose estimates were based on self-administered responses about personal behaviour, which relied on memories of residents. In this respect, incorrect behaviour records possibly resulted as memories have faded over time (‘recall bias’). However, the effects of these biases on dose distribution on a whole-prefecture basis seemed to be small.

「映像情報メディカル」の特集記事の一部として執筆。医療法施行規則改正による患者の被ばく線量管理に関し、防護の観点から執筆。

「保健の科学」の特集記事の一部として執筆。」放射線防護、放射線診断の被ばく線量、国内外の取り組みなどを紹介。

放射線防護人材の不足は国際的な課題であり、我が国でも行政のレベルで議論されるようになっ て久しい。東電福島第一原発事故を経験して放射線防護人材の重要性が社会的に認識されつつも、 人材不足の深刻度は増す一方である。2015 年には米国放射線防護審議会が放射線防護人材の不足 に関するステートメントを発表しているが、そのエビデンスとして過去20 年間の米国保健物理学 会の会員数の減少を報告している。そこで、日本放射線安全管理学会、日本放射線影響学会、日本 放射線事故･災害医学会、日本保健物理学会では、学会員の人数や年齢分布の時系列的変化に関す る共同的調査を実施した。 その結果、近年の会員数の推移は、学会によって異なることがわかった。また経時的に年齢分布 を比較した調査結果からは、20 代の会員の割合が増えているのに対し、40-50 代が減少しているこ とが明らかになった。その理由の一つとして、若い世代にとって放射線防護関連の（定常的）ポストを得ることが大きなハードルとなっていると考えられる。

日本医学物理学会が作成した、医学物理学の体系的教科書シリーズの一つである「医療放射線防護学」の全体を編集・監修した。

The medical management of individuals involved in a nuclear or radiological emergency requires specially trained personnel. Lessons learned from previous events have demonstrated that caring for these individuals calls for a multidisciplinary team of health care professionals if the response is to be effective. All hospitals offering medical radiation services (e.g. radiology, radiotherapy, nuclear medicine) have medical physicists who are part of the clinical team, with special responsibility for the proper and safe application of ionizing radiation. Using this reservoir of radiation protection experts in emergency and preparedness teams is good medical practice. Clinical medical physicists working in hospitals have in-depth knowledge of radiation dosimetry, dose reconstruction and dose measurement procedures. They constitute a unique group of professionals who, with the appropriate training, can provide effective support for emergency preparedness and response activities. Some sections of this publication were developed under the NA/21 Project supported by the Government of Japan within the IAEA Action Plan on Nuclear Safety, in cooperation with the International Organization for Medical Physics. This publication has been endorsed by the American Association of Physicists in Medicine, European Association of Nuclear Medicine, International Association of Radiopathology, International Federation of Red Cross and Red Crescent Societies, International Organization for Medical Physics and Latin American Association of Societies of Nuclear Medicine and Biology. The IAEA officers responsible for this publication were E.D. Herrera Reyes of the Incident and Emergency Centre, and T. Berris and A. Meghzifene of the Division of Human Health.

The medical management of individuals involved in a nuclear or radiological emergency requires specially trained personnel. Lessons learned from previous events have demonstrated that caring for these individuals calls for a multidisciplinary team of health care professionals if the response is to be effective. All hospitals offering medical radiation services (e.g. radiology, radiotherapy, nuclear medicine) have medical physicists who are part of the clinical team, with special responsibility for the proper and safe application of ionizing radiation. Using this reservoir of radiation protection experts in emergency and preparedness teams is good medical practice. Clinical medical physicists working in hospitals have in-depth knowledge of radiation dosimetry, dose reconstruction and dose measurement procedures. They constitute a unique group of professionals who, with the appropriate training, can provide effective support for emergency preparedness and response activities. Some sections of this publication were developed under the NA/21 Project supported by the Government of Japan within the IAEA Action Plan on Nuclear Safety, in cooperation with the International Organization for Medical Physics. This publication has been endorsed by the American Association of Physicists in Medicine, European Association of Nuclear Medicine, International Association of Radiopathology, International Federation of Red Cross and Red Crescent Societies, International Organization for Medical Physics and Latin American Association of Societies of Nuclear Medicine and Biology. The IAEA officers responsible for this publication were E.D. Herrera Reyes of the Incident and Emergency Centre, and T. Berris and A. Meghzifene of the Division of Human Health.

A survey on recognition, utilization, and evaluation for diagnostic reference levels (DRLs) after establishing Japan DRLs 2015 in the field of X-ray computed tomography (CT) was conducted for members of Japanese Society of Radiological Technology using web-based questionnaire system. The survey consisted of provincial branches to which respondents belong, their occupation, years of professional experience, years of experience in X-ray CT section, recognition of DRLs, and utilization and evaluation of DRLs in the field of X-ray CT section. Each survey item had one to eight questions. A total of 369 members completed the questionnaire. Among them, 295 out of 369 (79.9%) members knew that DRLs were released in Japan. After establishing the DRLs, 226 of 330 (68.5%) and 123 of 319 (38.6%) members investigated the doses used for adult and pediatric CT at their facilities, respectively. Although 345 of 369 (93.5%) members answered that DRLs are necessary for the field of X-ray CT, only 142 of 369 (38.5%) members thought that the established DRLs are enough to use in the field of X-ray CT. The survey has clarified the current status of recognition, utilization, and evaluation for DRLs in the field of X-ray CT after establishing the DRLs in Japan.

The present work describes that we try to construct a system that collects dose information that performed CT examination from multiple facilities and unified management. The results of analysis are compared with other National diagnostic reference level (DRL), and the results are fed back to each facility and the cause of the abnormal value is investigated for dose optimization. Medical information collected 139 144 tests from 33 CT devices in 13 facilities. Although the DRL of this study is lower than that of Japan DRL, it was higher than the DRL of each country. When collecting all the examination, it is thought that the variation of the dose due to the error other than the intended imaging site is large. In future, we should continue to collect information in order to DRL renewal and we also think that it is desirable to collect information on physique and detailed scan region as well.

国際放射線防護委員会(InternationalCommissiononRadiologicalProtection:ICRP)は，Publication73ʠRadiologicalProtectionandSafetyinMedicineʡ1)(「医学における放射線の防護と安全」)の中で「診断参考レベル(DiagnosticReferenceLevels:DRLs)」の考え方を導入した．更に，Publication103ʠThe2007RecommendationsoftheInternationalCommissiononRadiologicalProtectionʡ2)(「国際放射線防護委員会の2007年勧告」)では，医療放射線防護が「7.患者，介助者と介護者，生物医学研究志願者の医療被ばく」として章が独立し，「7.2.1.診断参考レベル」に記述された．放射線防護体系の中に明記されて以来，数多くの組織・国々で医療被ばく線量の調査が行われ，それらのデータを基にDRLsが設定されてきた．日本でも，その重要性は関係者らに認識されていたが，医療被ばくは法令上直接の規制対象になっていないため，公的な規制に取り入れられない状況が続いていた．しかし2015年，医療被ばく研究情報ネットワーク(JapanNetworkforResearchandInformationonMedicalExposure:J-RIME)が，オールジャパンとして初のDRLsといえる「最新の国内実態調査結果に基づく診断参考レベルの設定」3)を，関連学会・団体の協力を得てとりまとめた．これ以降，少しずつ，複数の学会などで取り組みが行われ，医療従事者の関心も高まってきている．このように，日本はDRLsに関して後塵を拝しているといわざるを得ないが，逆に見れば，他国の例が参考になるといえる．そこで，海外におけるDRLsについて，読者の参考になるデータ集としても用いることができるように，ここでまとめて紹介する.

A radiophotoluminescent glass dosimeter (RPLD) is a cumulative radiation dosimeter usually made of silver-activated phosphate glass. The silver atoms act as radiophotoluminescence (RPL) centres excited by ionizing radiation. The number of RPL centres excited is proportional to the absorbed dose to the RPLD. Since the first RPLD was produced in 1949, improvements have been made to the reading precision and reliability[1]. The latest products, rod-like dosimeters of a few millimetres in size, measure the absorbed dose that can be evaluated with an uncertainty of about 1 % to 2 % (k = 1) in certain conditions[2] to [5]. The RPL centres do not disappear after readout. Therefore, repeated readouts for a single exposure is possible. The results are stable and good accuracy of the signal readouts is possible. In addition, since the RPL centres once formed are hardly affected by fading, it is suitable in long-term dose measurement with retention capacity. RPLDs can be reused by annealing at high temperature. RPLDs have been widely used for personal dosimetry and environmental radiation measurements[6] to [7].They are also used for radiation dose assessment of patients and staff in the field of radiation medicine, including interventional radiology, external radiotherapy, and brachytherapy[8] to [21]. Due to their advantages of compactness, repeatable readout, good precision, and small fading, RPLDs have been recently used as a dosimeter for dosimetric external audits in external radiotherapy with high-energy X‑rays[22] to [27]. Thermoluminescent Dosimeter (TLD) and optically stimulated luminescent dosimeter (OSLD) have also been used for the audits. The three dosimeters, RPLD, TLD, and OSLD, are passive solid-state dosimeters and have some similar characteristics. However, there are variations in the handling, reading methodology, and dose evaluation, including tissue-equivalency. This document focuses on the RPL dosimetry from the viewpoint of the dosimetry audit in MV X‑ray radiotherapy highlighting the procedures for handling, reading, and corrections to the response dependency of beam quality and dose.

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.

「月刊インナービジョン」特‌集 医療被ばくの正当化と最適化に向けて─線量管理義務化の動向と医療機関に求められる対応─ I‌‌ 線量管理義務化に向けた国内動向と海外の現状 一部執筆

Background: The Japan Society of Medical Physics (JSMP) was originated from the physics committee of Japan Radiological Society (JRS) established in 1953. In 2000, the Japanese Association of Radiological Physicist (JARP) and the Japanese Association of Medical Physicists (JAMP) were merged into the JSMP. The JSMP was certified as a Public Interest Incorporated Association in May 2018. Activities: The current activities have been to hold the academic meetings, to study on physics and technologies in medicine, to publish the academic English journal “Radiological Physics and Technology” with the Japanese Society of Radiological Technology (JSRT), which is one of the AFOMP official journals, and Japanese journal, to cooperate with domestic and overseas organizations and to perform other necessary activities. We have also been one of the property contributors of general incorporated foundation of Japanese Board for Medical Physicist Qualification (JBMP) and involved in the medical physicist certification in Japan. Future Tasks: The situations around medical physics and medical physicist have been varying due to the progress of medical and information technologies as well as recent social and economic factors. The well-timed implementation for the situations should be required, so we will discuss and perform the activities to contribute the human health by expanding the scope of activities more interdisciplinary and internationally. The Japan Radiology Congress 2019 (JRC2019) of which JSMP is one of host organizations will be held in Yokohama next year. Any AFOMP members can participate in the congress with no fee, and can be candidate for the presentation awards., The 18th Asia-Oceania Congress of Medical Physics (AOCMP) and the 16th South-East Asia Congress of Medical Physics (SEACOMP)

Purpose: In radionuclide therapy, beta and alpha particle emitters have been used as weakly penetrating radiation sources. However, the conventional dose calculation method for photons would not always be suitable for radionuclide therapy due to the short range in the body. The purpose of this study is to make a model of dose estimations for weakly penetrating radiation in radionuclide radiotherapy. Methods: The issues of dose estimations to be considered in radionuclide therapy are the heterogeneously distributed doses and the higher dose levels for the possibility of not only stochastic but also deterministic effects. The former depends on the local concentrations of radionuclide with high radioactivity, and the latter is related to the physical and protection quantities with respect to radiation and tissue weighting factors. The dose distributions are determined based on the diagnostic images, and the exposed volumes are considered in each dose levels. Results: The absorbed fractions from the source to target organs can be calculated considering the volumes as the sources in which the radionuclide concentrated. The wide range dose gradient in one organ requires the reconsideration of the concept of averaged absorbed dose, radiation and tissue weighting factors. The model estimates the internal doses in radionuclide therapy considering both stochastic and deterministic effects. This method can be applied for other radiotherapy and interventional radiology., The 18th Asia-Oceania Congress of Medical Physics (AOCMP) and the 16th South-East Asia Congress of Medical Physics (SEACOMP)

「公衆衛生」特集「『放射線リテラシー』をめぐる課題」一部原稿執筆

「月刊エネルギーレビュー」特集記事「福島の復興に向け行動する人々」一部執筆

X-ray CT (Computed Tomography) is very popular as a useful diagnostic method, so it is important to assess high exposure dose of CT in terms of justification and optimization. WAZA-ARI version 2 (WAZA-ARIv2, https://waza-ari.nirs.qst.go.jp/) is the web-based open system for X-ray CT dose calculation, which has been developed by National Institute of Radiological Sciences (NIRS), Oita University of Nursing and Health Sciences and the Japan Atomic Energy Agency (JAEA). The organ doses of various CT exposures were calculated using Monte Carlo simulation and voxel phantoms. In WAZA-ARIv2, can provide organ doses taking into consideration of the body type of patient using Japanese voxel phantoms developed by JAEA. And it can also provide exposure doses of children using child voxel phantoms developed by the University of Florida. In this system selectable CT scanners are 31 models. The number of CT models in WAZA-ARIv2 system is still increasing. Furthermore, we added the database function of storing the calculation results in each facility in order to check the exposure level of the CT examination in the facility in the stored distribution data in Japan. In January 2015, WAZA-ARIv2 system started, and currently over one thousand users are registered. In order to acquire more data on the actual situation of medical exposure in Japan, we plan to expand the number of users and to improve functions of WAZA-ARIv2 system. In this presentation, we will report the development and progress of WAZA-ARIv2 system., World Congress on Medical Physics and Biomedical Engineering 2018 (WC2018)

リアルタイムなMaximumESDの予測法を確立するため，複数個のRPLDを頭部全体に配置して，頭部診断血管撮影におけるESDの分布ならびにMaximumESD，水晶体線量を評価した．更に血管撮影装置関連パラメータによるMaximumESDの予測精度について検討を行った．

Direct measurements for internal dose estimates were performed at National Institute of Radiological Sciences (NIRS) on seven highly exposed workers of Tokyo Electric Power Company (TEPCO) and eight NIRS staff members who were first responders to the accident at the TEPCO Fukushima Daiichi Nuclear Power Station. For the TEPCO workers, the measurements were performed by both the whole-body counting and thyroid counting. The average effective half-life values of 131I in the thyroid and of 134Cs and 137Cs in the body were 7.8 days, 92.0 days and 104.3 days, respectively. These values were consistent with biokinetic models proposed by the International Commission on Radiological Protection (ICRP). For the NIRS staff members, the thyroid counting was made on the day when they had returned. The amount of 131I that was detected in the thyroid of all the eight subjects was small (~100 Bq) even though they went to places near the site of the accident in its early stage. This level was found to be comparable to those of other NIRS staff members who stayed in the Chiba area (about 200 km south of the reactor) during the early stage of the accident.

Surface dose monitoring in patients and physicians during 29 uterine artery embolisation (UAE) procedures was performed using photoluminescence dosemeters and thermo-luminescence dosemeters. Organ or tissue doses were measured with an anthropomorphic phantom using UAE exposure conditions averaged from the 29 cases, and effective doses were estimated for the patient. Entrance surface dose of the patients at the maximum dose position ranged from 121.5 to 1650 mGy. Estimated doses ranged from 3.16 to 43 mGy for the ovary and from 3.8 to 51.8 mGy for the uterus. The effective dose was 1.09-14.8 mSv. Monitored doses on the body surface of physicians were relatively high in the upper arm (5.41+-1.52 to 163+-17.25 mGy) and the hand and fingers (0.85+-1.18 to 222+-16.4 mGy).