|納冨 昭弘（のうとみ あきひろ）||データ更新日：2022.05.28|
|1.||齋藤秀敏、椎山謙一、岩元新一郎、古徳純一、納冨昭弘、鬼塚昌彦、橘昌幸、眞正浄光、千田浩一, 診療放射線基礎テキストシリーズ 放射線計測学, 共立出版, 2020.03.|
|2.||納冨 昭弘, 放射線計測学 (医学物理学教科書シリーズ), 国際文献社, 2015.03, 著者27名による共著の編集。一部、執筆担当。.|
|3.||納冨 昭弘, 「原子力・量子・核融合事典」 5.1.3 線量測定 ・線量測定と線量変換法, 丸善出版, 2014.12, 一部、執筆担当。.|
|1.||Akihiro Nohtomi, Hideya Maeda, Naoya Sakamoto, Genichiro Wakabayashi, Takushi Takata, Yoshinori Sakurai, First optical observation of 10B-neutron capture reactions using a boron-added liquid scintillator for quality assurance in boron neutron capture therapy, Radiological Physics and Technology, 2021.11, 10B-neutron capture was observed optically using a boron-added liquid scintillator. Trimethyl borate was dissolved in a commercially available liquid scintillator at natural boron concentrations of approximately 1 wt% and 0.25 wt%. The boron-added liquid scintillator was placed in a phantom quartz bottle and irradiated by thermal neutrons (~105 n/[cm2 s]) for 150, 300, and 600 s. The luminescence of the liquid scintillator was clearly observed using a cooled charge-coupled device (CCD) camera during irradiation. The luminance value recorded by the CCD camera was proportional to the duration of irradiation by thermal neutrons. The luminescence distribution showed reasonable agreement with that of energy deposition by Li and alpha particles from 10B-neutron capture reactions calculated via Monte Carlo simulations. When trimethyl borate was not dissolved in the liquid scintillator (0 wt% natural boron), no visible luminescence was observed even after 600 s of irradiation. These findings demonstrate that the observed luminance originates from the Li and alpha particles generated by 10B-neutron capture reactions. Consequently, the luminescence distribution is directly related to the boron dose of the liquid scintillator. To the best of our knowledge, direct experimental optical observations of boron dose distribution have not yet been reported. This novel technique will be useful for quality assurance in boron neutron capture therapy (BNCT) because instantaneous neutron irradiation may be sufficient for the observing the intense neutron beam used in clinical BNCT (~109 n/[cm2 s]), and quick evaluation of the boron dose distribution is expected to be feasible..|
|2.||Akihiro Nohtomi, Yui Kanzaki, Naoya Sakamoto, Hideya Maeda, Observation of water luminescence for diagnostic 120-kV X-rays by using PMT and CCD camera, Nuclear Instruments and Methods in Physics Research A, 988 , 164935, 2021.01, Luminescence emitted from water was recently observed by Yamamoto et al. for X-rays with lower energy than the Cerenkov-light threshold. This phenomenon contradicts the conventional consensus that such low-energy photons cannot generate luminescence. Because properties and mechanism of this phenomenon have not been revealed yet, we carried out a series of observations of water luminescence during irradiation of diagnostic 120-kV X-rays by using a photomultiplier tube (PMT) and a charge-coupled device (CCD) camera. As a result of PMT measurement, the light yields owing to luminescence per unit dose deposition to water decreased almost linearly with the increase in the pulse duration time; approximately 25 % reduction of light yield was observed as the duration time increased from 0.025 s to 0.5 s. Therefore, the luminance intensity was not simply proportional to the dose deposition to water. In addition to water, sulfuric acid was used for luminescence imaging by a CCD camera for comparison. The profile curve of luminance along the beam center axis for sulfuric acid showed a somewhat different tendency in comparison to that for water; a notable bump appeared in the entry region of the X-rays. Based on these observations, the possibility of the contribution of sonoluminescence to the water luminescence can be discussed..|
|3.||Yumika Hanada, Akihiro Nohtomi, Junichi Fukunaga, Yoshiyuki Shioyama, DEVELOPMENT OF A NEUTRON DOSIMETRY SYSTEM BASED ON DOUBLE SELF-ACTIVATED CsI DETECTORS FOR MEDICAL LINAC ENVIRONMENTS, Radiation Protection Dosimetry, doi:10.1093/rpd/ncaa218, 1-9, 2020.11, In the present study, by using double self-activated CsI detectors, the development of a neutron dosemeter system whose response indicates better agreement with the International Commission on Radiological Protection-74 rem-response was carried out to simply evaluate the neutron dose with high accuracy. The present double neutron dosemeter system, using a slow-neutron dosemeter (thermal to 10 keV) and a fast-neutron dosemeter (above 10 keV), consists of CsI scintillators wrapped with two types of neutron energy filtering materials: polyethylene and B4C silicon rubber. After optimization of each filter thickness, to confirm the validity of our method, the neutron ambient dose equivalents under several operating conditions of medical linear accelerators (Linacs) were evaluated using a Monte Carlo simulation and an experiment with the present dosemeter. From these results, the present dosimetry system has enabled a more accurate neutron dose evaluation than our conventional dosemeter, and the present dosemeter was suitable for the neutron dosimetry for 10 MV Linac environments..|
|4.||Taishi Ueki, Akihiro Nohtomi, Genichiro Wakabayashi, Junichi Fukunaga, Toyoyuki Kato, S. Ohga, A design study of application of the CsI self-activation method to the neutron rem-counter technique, Radiation Measurements, 10.1016/j.radmeas.2019.106181, 128, 2019.09, [URL], A design study of application of the CsI self-activation method to the “neutron rem-counter technique” was investigated. A CsI crystal served as both the main target material and 4π counter of neutron activation method in our proposed CsI self-activation method. A commercially available CsI gamma-ray dosimeter was selected as the neutron detector and surrounded with several neutron filters made of polyethylene and silicon rubber containing B4C. The geometric structure of these neutron filters was optimized by a Monte Carlo calculation to make the neutron response similar to the ICRP-74 rem-response. Optimization of this method, the residual sum of squares (RSS) of the calculated neutron response and the ICRP-74 rem-response were minimized by changing the thickness of each filter sequentially. In addition, experimental verification using a Pu–Be source and photoneutrons from a 10 MV-X medical linac has been conducted. From these results, it is concluded that it may be practical for evaluating neutron ambient dose-equivalent simply around medical linacs..|
|5.||Akihiro NOHTOMI , Masaaki TOKUNAGA, Genichiro WAKABAYASHI, Kiyomitsu SHINSHO, Neutron Distribution Measurement by the Self-activation of a CsI Plate with CCD Camera using a Decaying Self-activation Imaging Technique, JPS Conf. Proc. 24, 1, 011041, 2019.01, Neutron intensity distribution on a CsI scintillator plate has been observed by a CCD camera and analyzed by using a “decaying self-activation imaging technique”. The decaying self-activation imaging, which has been proposed recently by our group, is based on the analysis of time variation of specific radio-activities generated and remained inside the CsI plate after the termination of neutron irradiation. The luminance distributions of a CsI plate are recorded every one minute as a series of images by a cooling type CCD camera with a telescope lens in a black box. Then the time variations of luminance (mean pixel values) of the images are fitted on a “pixel-by-pixel basis” with a multi-exponential function. By this, two components of 128I (half life : 25 min) and 134mCs (half life : 174 min) are extracted as the fitting curves. The initial luminance values of individual component of radioactivity, which correspond to the values at the termination of neutron irradiation, are plotted as separate images. A conversion factor between the generated activity in a CsI plate and the observed luminance value is evaluated as “light yield”..|
|6.||Ryosuke Kurihara, Akihiro Nohtomi, Genichiro Wakabayashi, Yoshinori Sakurai, Hiroki Tanaka, Preliminary design study of a simple neutron energy spectrometer using a CsI self-activation method for daily QA of accelerator-based BNCT, journal of nuclear science and technology, 10.1080/00223131.2018.1523757, 56, 1, 70-77, 2019.01, [URL], For recent boron neutron capture therapy (BNCT), accelerator-based neutron sources have been actively developed in place of reactor-based neutron sources. In this study, a novel neutron energy spectrometer for the daily quality assurance (QA) of BNCT was designed on the basis of a CsI self-activation method for accelerator-based neutron sources. The spectrometer design was optimized in terms of its energy resolution. To verify its applicability to high-intensity BNCT neutron fields, some practical simulations were performed. It was shown that the designed spectrometer was able to evaluate a neutron energy spectrum in approximately 900 s after an instantaneous neutron irradiation. In addition, its energy resolution was sufficient for detecting an unexpected distortion in the spectrum. The results confirm that the designed spectrometer can be employed for the daily QA of BNCT to check that the expected spectrum remains unchanged..|
|7.||Ryo Kakino, Akihiro Nohtomi, Genichiro Wakabayashi, Improvement of neutron spectrum unfolding based on three-group approximation using CsI self-activation method for evaluation of neutron dose around medical linacs, Radiation Measurements, 10.1016/j.radmeas.2018.06.021, 116, 40-45, 2018.09, [URL], We previously evaluated ambient neutron dose equivalent by using the self-activation of a CsI scintillator around a high-energy medical linear accelerator (linac) 128I saturated activities were successfully converted to neutron spectrum and ambient neutron dose equivalent by neutron spectrum unfolding with the “three-group approximation.” The principle of the three-group approximation is based on the assumption of fixed shapes of neutron energy spectra for each of the three energy regions to evaluate the neutron spectrum effectively. However, such a neutron dose evaluation with the unfolding method might be affected by the difference between the actual fast neutron energy spectrum and the assumed spectrum. In the present work, we modified the unfolding method by taking into account the differences in the shapes of fast neutron energy spectra for various medical linacs. We verified the unfolding method using Monte Carlo simulation with several neutron spectra obtained from published research articles. The modified three-group approximation evaluates the neutron doses more accurately than the conventional unfolding method..|
|8.||Soichiro Honda, Akihiro Nohtomi, Keita Machidori, Genichiro Wakabayashi, Shape distortion of 128I ß- spectrum observed by a self-activated CsI(Tl) scintillator for high-sensitivity neutron measurements, Nuclear Instruments and Method in Physics Research A, 2017.04, The factors causing the distortion of the 128I ß- spectrum detected by a self-activated CsI(Tl) scintillator were studied to verify the correctness of the spectral shape and the appropriateness of the discrimination setting for ß-particle counting by the scintillator. These criteria are essential for the correct evaluation of radioactivity generated in a scintillator volume by the self-activation method, which was recently proposed by our group.
A pulse height defect caused by the partial escape of ß! particles from the surface of the scintillator crystal shifts the ß! spectrum toward the lower-energy region when smaller CsI(Tl) scintillators are used (the ß-escape effect). For larger CsI(Tl) scintillators, an increase in pulse height caused by the summing of 0.443 MeV prompt γ-rays from the excited state of the 128I daughter nuclide (128Xe) affects the shape of the ß! spectrum considerably, resulting in a shift toward the higher-energy region (the γ-summing effect). The extent of the contributions of these two effects was examined by a Monte Carlo simulation of various cubical CsI(Tl) crystals of different sizes. It was found that the distortions caused by those two effects effectively cancel each other out for a medium-size cubical CsI(Tl) crystal with a side length of approximately 3 cm. This finding is very useful for the practical applications of the self-activation method.
In addition to the factors mentioned above, the efficiency of scintillation light collection by the photodetectors also affects the shape distortion of the ß! spectrum slightly through spectral line broadening due to the degradation of the energy resolution. This effect was estimated using a simple model with different discrimination settings for ß pulse counting.
|9.||松尾亮子, 納冨昭弘, 栗原凌佑, 若林源一郎, 反跳陽子比例計数管によるオンラインn/γ分離測定へのベイズの定理の応用, 応用物理学会・放射線分科会
, 40, 1, 35-40, 2017.03.
|10.||Akihiro Nohtomi, Genichiro Wakabayashi, Hiroyuki Kinoshita, Soichiro Honda, Ryosuke Kurihara, Junichi Fukunaga, Yoshiyuki Umezu, Yasuhiko Nakamura, Saiji Ohga, Katsumasa Nakamura, High Sensitive Neutron-detection by using a Self-activation of Iodine-containing Scintillators for the Photo-neutron Monitoring around X-ray Radiotherapy Machines, JPS Conf. Proc. 11, 050002 (2016), 2016.11, A novel method for evaluating the neutron dose-equivalent as well as neutron fluence around high-energy X-ray radiotherapy machines has been proposed and examined by using the self-activation of a CsI scintillator. Several filtering conditions were used to extract energy information of the neutron field. The shapes of neutron energy spectra were assumed to be practically unchanged at each three energy regions (thermal, epi-thermal and fast regions) for different irradiations around an X-ray linac whose acceleration potential was fixed to be a certain value. In order to know the actual neutron energy spectrum, an unfolding process was carried out for saturated activities of 128I generated inside the CsI scintillator under different filtering conditions; the response function matrix for each filtering condition was calculated by a Monte Carlo simulation. As the result, neutron dose-equivalent was estimated to be 0.14 [mSv/Gy] at 30 cm from the isocenter of linac. It has been revealed that fast neutron component dominated the total dose-equivalent..|
|11.||Akihiro Nohtomi, Ryousuke Kurihara, Hiroyuki Kinoshita, Soichiro Honda, Masaaki Tokunaga, Heita Uno, Kiyomitsu Shinsho, Genichiro Wakabayashi, Yusuke Koba, Junichi Fukunaga, Yoshiyuki Umezu, Yasuhiko Nakamura, Saiji Ohga, An application of CCD read-out technique to neutron distribution measurement using the self-activation method with a CsI scintillator plate, Nuclear Instruments and Method in Physics Research A, A832, 21-23, 2016.06, In our previous paper, the self-activation of an NaI scintillator had been successfully utilized for detecting photo-neutrons around a high-energy X-ray radiotherapy machine; individual optical pulses from the self-activated scintillator are read-out by photo sensors such as a photomultiplier tube (PMT). In the present work, preliminary observations have been performed in order to apply a direct CCD read-out technique to the self-activation method with a CsI scintillator plate using a Pu-Be source and a 10-MV linac. In conclusion, it has been revealed that the CCD read-out technique is applicable to neutron measurement around a high-energy X-ray radiotherapy machine with the self-activation of a CsI plate. Such application may provide a possibility of novel method for simple neutron dose-distribution mea- surement..|
|12.||Akihiro Nohtomi, Yoko Ariyoshi, Momoko Yamauchi, Hiroyuki Kinoshita, Soichiro Honda, Genichiro Wakabayashi, Junichi Fukunaga, H. Akamine, Yoshiyuki Umezu, Yasuhiko Nakamura, Study on high-sensitive neutron-detection by the self-activation method with a CsI(Tl) scintillator, Radiation Detectors and Their Uses, Proceedings of the 29th Workshop on Radiation Detectors and Their Uses (KEK Proceedings 2015-8), 50-53, 2015.12.|
|13.||Akihiro Nohtomi, Genichiro Wakabayashi, Accuracy of neutron self-activation method with iodine-containing scintillators for quantifying 128I generation using decay-fitting technique, Nuclear Instruments and Method in Physics Research A, A800, 2015.08, Decay curves of 128I activity were numerically simulated by a computer program for various conditions including different initial count rates (R0) and background rates (RB), as well as counting statistical fluctuations. .|
|14.||薮田和利, 門前 一, 田村昌也, 鶴田隆夫, 伊藤哲夫, 納冨 昭弘, 西村恭昌, 高エネルギーX線治療におけるCR-39を用いた中性子測定システム, 医学物理学会誌, 34, 3, 139-147, 2015.01, 固体飛跡検出器であるCR-39を用いて、高エネルギーX線発生装置から発生する光中性子強度を測定する方法を確立し、その応答をもとにして中性子個人線量当量を評価するシステムを構築してその実用性について検討した。医療用直線加速器で発生する中性子エネルギーを特定して、寄与率を補正することにより、中性子個人線量当量の測定が可能であることが示された。.|
|15.||Genichiro Wakabayashi, Akihiro Nohtomi, Eriko Yahiro, Fujibuchi Toshioh, Junichi Fukunaga, Yoshiyuki Umezu, Yasuhiko Nakamura, Katsumasa Nakamura, Makoto Hosono, Tetsuo Itoh, Applicability of self-activation of an NaI scintillator for measurement of photo-neutrons around a high-energy X-ray radiotherapy machine, Radiological Physics and Technology, 8, 1, 125-134, 2015.01, NaIシンチレータに含まれるヨウ素に自己放射化に基づく高感度中性子検出方法を提案し、研究用原子炉ならびにがん治療用X線発生装置で原理検証実験を行った。その結果、〜10^2[n/cm2/s]程度までの熱中性子束を測定可能であることが判明した。この装置を用いて、高エネルギーX線治療装置から発生する光中性子の量を、オンラインにてサブリアルタイムで測定出来るシステムが実現できることが示唆された。.|
|16.||八尋絵莉子, 納冨昭弘, 若林源一郎, 藤淵俊王, 梅津芳幸, 福永淳一, 中西大樹, 長峰周治, 中村泰彦, NaIシンチレータを用いた高感度中性子検出法の研究, 放射線、Vol.40, No.1 (2014), 55-58, 2014.03.|
|17.||Daiki Nakanishi, Akihiro Nohtomi, Ryoji Tanaka, Genichro Wakabayashi, A method of neutron-energy evaluation based on the position distribution of recoil protons, Progress in Nuclear Science and Technology, 4, 653-656, 2014.03, Cone-like acryl converters have been used for transforming the energy-distribution information of incident fast neutrons into the spatial-distribution information of recoil protons. The characteristics of neutron–proton conversion have been studied up to around 10 MeV by using an imaging plate (IP). A notable and interesting signal enhancement due to recoil protons generated in an acryl converter was observed on IP images for irradiation with a 252Cf source. Similar experiments were also performed in the radiation field of a research nuclear reactor and an accelerator-based neutron generator. A Monte Carlo calculation was carried out in order to understand the spatial distributions of the signal enhancement by recoil protons; these distributions promisingly involve the energy information of incident neutrons in principle. Consequently, it has been revealed that the neutron energy evaluation is surely possible by analyzing the spatial distributions of signal enhancement that is caused by recoil protons..|
|18.||Akihiro Nohtomi, , A method of neutron energy evaluation by using an imaging plate and cone-like acryl converters with a geometrical modulation concept, Nuclear Instruments and Method in Physics Research A , A633, 36, 2011.03, Cone-like acryl converters have been used for transforming the energy-distribution information of incident fast neutrons into the spatial-distribution information of recoil protons. The characteristics of neutron–proton conversion have been studied up to around 10 MeV by using an imaging plate (IP). A notable and interesting signal enhancement due to recoil protons generated in an acryl converter was observed on IP images for irradiation with a 252Cf source. Similar experiments were also performed in the radiation field of a research nuclear reactor and an accelerator-based neutron generator. A Monte Carlo calculation was carried out in order to understand the spatial distributions of the signal enhancement by recoil protons; these distributions promisingly involve the energy information of incident neutrons in principle. Consequently, it has been revealed that the neutron energy evaluation is surely possible by analyzing the spatial distributions of signal enhancement that is caused by recoil protons..|
2022.04～2024.03, 日本医学物理学会, 理事.
2020.04～2023.03, 日本医学物理学会, 理事.
2018.10～2020.05, 第119回日本医学物理学会学術大会, 実行委員長.
2015.11～2022.04, BNCT推進協議会, 人材育成WG.
2015.11～2022.04, 日本中性子捕捉療法学会, BNCT人材育成委員会委員.
2011.10～2012.04, 日本医学物理学会, 第103回 学術大会 プログラム委員.
2012.06～2014.06, 日本医学物理学会, 医学物理学 教科書 ad hoc 委員会 委員.
2020.05.13～2020.06.13, 日本医学物理学会, 大会実行委員長.
2019.04.13～2016.04.13, 日本医学物理学会, 座長（Chairmanship）.
2018.04.11～2018.04.13, 日本医学物理学会, 座長（Chairmanship）.
2016.09.14～2016.09.14, 応用物理学会, 座長（Chairmanship）.
2016.09.14～2016.09.14, 応用物理学会 放射線分科会シンポジウム, 座長（Chairmanship）.
2016.04.17～2016.04.17, 日本医学物理学会, 座長（Chairmanship）.
2016.01.18～2016.01.21, ISRD2016, 座長（Chairmanship）.
2015.09.18～2015.09.20, 日本医学物理学会, 座長（Chairmanship）.
2015.04.16～2015.04.19, 日本医学物理学会, 座長（Chairmanship）.
2012.06.16～2012.06.17, 日本保健物理学会 第45回研究発表会, 座長（Chairmanship）.
2011.09.29～2011.10.01, 6th Japan-Korea Joint Meeting on Medical Physics (JKMP), 11th Asia-Oceania Congress of Medical Physics（AOCMP）, 座長（Chairmanship）.
2016.09.14～2016.09.14, 応用物理学会 シンポジウム「放射線医療現場における受動型放射線検出器による計測手法の最近の進展」, 放射線分科会 シンポジウム企画、座長、「放射線」特集号編集担当.
2015.01.18～2015.01.21, ISRD2016, プログラム編集委員、moderator.
2012.09.02～2012.09.07, ICRS-12&RPSD-2012, プログラム編集委員.
2012.06.16～2012.06.17, 日本保健物理学会, 座長.
2019.04～2020.03, 日本放射線技術学会「放射線計測学」 共立出版(株), 国内, 執筆分担.
2014.04～2020.12, 日本医学物理学会誌「医学物理」, 国内, 編集委員.
2012.01～2023.05, Journal of Nuclear Science and Technology, 国内, 査読委員.
2017.01～2023.05, Physics in Medicine and Biology, 国際, 査読委員.
2017.04～2023.05, Proceedings of the Japan Academy, Series B, 国内, 査読委員.
2017.04～2023.05, Medical Physics, 国際, 査読委員.
2013.10～2023.05, 日本放射線技術学会誌, 国内, 査読委員.
2013.10～2023.05, Journal of Radiation Research, 国際, 査読委員.
2012.10～2023.05, Radiological Physics and Technology, 国際, 編集委員長.
2012.09～2013.12, Proceedings of ICRS12 & RPSD 2012(published as Progress of Nuclear Science and Technology), 国内, 編集委員.
2012.06～2016.06, 日本医学物理学会 医学物理学教科書シリーズ「放射線計測学」, 国内, 編集委員.
2019 IEEE NSS/MIC (Manchester), UnitedKingdom, 2019.10～2019.11.
2018 IEEE NSS/MIC (Sydney), Australia, 2018.11～2018.11.
上海復旦大学, Fudan University, China, 2018.10～2018.10.
2017 IEEE NSS/MIC (Atlanta), UnitedStatesofAmerica, 2017.10～2017.10.
台湾国立清華大学, National Tsing Hua University, Taiwan, 2016.09～2016.09.
高麗大学, Korea University, Korea, 2015.03～2015.03.
JSMP/KSMP Joint meeting, Korea, 2014.09～2014.09.
National Physical Laboratory (NPL), Oxford University, Department of Physics, UnitedKingdom, 2011.12～2012.02.
第117回 日本医学物理学会学術大会 President's Award Gold, 日本医学物理学会, 2019.04.
第65回応用物理学会春季学術講演会・放射線分科会学生ポスター賞(共同受賞), 応用物理学会・放射線分科会, 2018.03.
第113回 日本医学物理学会学術大会 Cypos 大会長賞 , 日本医学物理学会, 2017.04.
Doi Award (土井賞) in Radiation Therapy Physics, Radiological Physics and Technology , 2016.04.
ICRR2015 Excellent Poster Award, 15th International Congress of Radiation Research, 2015.05.
第105回 日本医学物理学会学術大会 大会長賞, 日本医学物理学会, 2013.04.
第104回 日本医学物理学会学術大会 大会長賞, 日本医学物理学会, 2012.09.
日本原子力学会論文賞, 日本原子力学会, 1995.03.
2022年度～2024年度, 基盤研究(C), 代表, ホウ素中性子捕捉療法の品質保証の為のホウ素線量分布直接測定法の開発.
2019年度～2021年度, 基盤研究(C), 代表, ホウ素中性子捕捉療法における中性子測定に適した自己放射化有機シンチレータの開発.
2016年度～2018年度, 基盤研究(C), 代表, 放射線治療で発生する中性子被ばく評価の為の簡便で高精度な分布測定システムの開発.
2013年度～2015年度, 挑戦的萌芽研究, 代表, GM管の様に使いやすい高速中性子サーベイメータの開発についての基礎研究.