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Journal Articles

Japanese pediatric and adult atomic bomb survivor dosimetry; Potential improvements using the J45 phantom series and modern Monte Carlo transport

Griffin, K. T.*; Sato, Tatsuhiko; Funamoto, Sachiyo*; Chizhov, K.*; Domal, S.*; Paulbeck, C.*; Bolch, W.*; Cullings, H. M.*; Egbert, S. D.*; Endo, Akira; et al.

Radiation and Environmental Biophysics, 61(1), p.73 - 86, 2022/03

To evaluate the potential dosimetry improvements that would arise from their use in a Dosimetry System (DS) at RERF, we have evaluated organ doses in the J45 series using the environmental fluence data for twenty generalized survivor scenarios pulled directly from the current DS. The energy- and angle-dependent gamma and neutron fluences were converted to a phase space source term for use in MCNP6, a modern radiation transport code. Overall, the updated phantom series would be expected to provide dose improvements to several important organs, including the active marrow, colon, and stomach wall (up to 20%, 20%, and 15% impact on total dose, respectively). The impacts on dosimetry were especially significant for neutron dose estimates (up to a two-fold difference) and within organs which were unavailable in the previous phantom series, such as the skin, esophagus, and prostate.

Journal Articles

To be a global center for neutron utilization; Resumption of operation of JRR-3

Endo, Akira

Hokeikyo Nyusu, (68), P. 1, 2021/10

This article introduces resumption of utilization of the research reactor JRR-3 at the Nuclear Science Research Institute, JAEA. JRR-3 resumed its operation in July 2021 for the first time in 10 years and 7 months, after the confirmation of its conformity to the new regulatory requirements established by the Nuclear Regulatory Commission following the accident at the TEPCO's Fukushima Daiichi Nuclear Power Plant in March 2011. JRR-3 is expected to produce many research results in academic and industrial applications as a research center for neutron science in collaboration with the Materials and Life Science Facility (MFL) of the Japan Proton Accelerator Research Complex (J-PARC).

Journal Articles

Dosimetric impact of a new computational voxel phantom series for the Japanese atomic bomb survivors; Methodological improvements and organ dose response functions

Sato, Tatsuhiko; Funamoto, Sachiyo*; Paulbeck, C.*; Griffin, K.*; Lee, C.*; Cullings, H.*; Egbert, S. D.*; Endo, Akira; Hertel, N.*; Bolch, W. E.*

Radiation Research, 194(4), p.390 - 402, 2020/10

 Times Cited Count:2 Percentile:0.01(Biology)

Owing to recent advances in computational dosimetry tools, it is desirable to update the dosimetry system for the atomic-bomb survivors as it was established by DS02. In the current study, we have investigated the possible impact of introducing not only the J45 phantom series but also various methodological upgrades to the DS02 dosimetry system. It was found that the anatomical improvement in the J45 phantom series is the most important factor leading to potential changes in survivor organ doses. In addition, this study established a series of response functions which allows for the rapid conversion of the unidirectional quasi-monoenergetic photon and neutron fluences to organ doses within the J45 adult phantoms. This system of response functions can be implemented within a revision to the DS02 dosimetry system and used for future updates to organ doses within the Life Span Study of the atomic-bomb survivors.

Journal Articles

Controlled growth of boron-doped epitaxial graphene by thermal decomposition of a B$$_{4}$$C thin film

Norimatsu, Wataru*; Matsuda, Keita*; Terasawa, Tomoo; Takata, Nao*; Masumori, Atsushi*; Ito, Keita*; Oda, Koji*; Ito, Takahiro*; Endo, Akira*; Funahashi, Ryoji*; et al.

Nanotechnology, 31(14), p.145711_1 - 145711_7, 2020/04

 Times Cited Count:3 Percentile:58.93(Nanoscience & Nanotechnology)

We show that boron-doped epitaxial graphene can be successfully grown by thermal decomposition of a boron carbide thin film, which can also be epitaxially grown on a silicon carbide substrate. The interfaces of B$$_{4}$$C on SiC and graphene on B$$_{4}$$C had a fixed orientation relation, having a local stable structure with no dangling bonds. The first carbon layer on B$$_{4}$$C acts as a buffer layer, and the overlaying carbon layers are graphene. Graphene on B$$_{4}$$C was highly boron doped, and the hole concentration could be controlled over a wide range of 2$$times$$10$$^{13}$$ to 2$$times$$10$$^{15}$$ cm$$^{-2}$$. Highly boron-doped graphene exhibited a spin-glass behavior, which suggests the presence of local antiferromagnetic ordering in the spin-frustration system. Thermal decomposition of carbides holds the promise of being a technique to obtain a new class of wafer-scale functional epitaxial graphene for various applications.

Journal Articles

Dosimetric impact of a new computational voxel phantom series for the Japanese atomic bomb survivors; Pregnant females

Paulbeck, C.*; Griffin, K.*; Lee, C.*; Cullings, H.*; Egbert, S. D.*; Funamoto, Sachiyo*; Sato, Tatsuhiko; Endo, Akira; Hertel, N.*; Bolch, W. E.*

Radiation Research, 192(5), p.538 - 561, 2019/08

 Times Cited Count:4 Percentile:42.47(Biology)

An important cohort of the atomic bomb survivors are pregnant females exposed to the photon and neutrons fields at both Hiroshima and Nagasaki, as well as their children who were exposed ${it in-utero}$. In the present study, we present a new J45 (Japanese 1945) series of high-resolution phantoms of the adult pregnant female at 8-week, 15-week, 25-week, and 38-week post-conception. As for the maternal organ doses, the use of organ doses in a non-pregnant female were shown, in general, to overestimate the corresponding organ doses in the pregnant female, with greater deviations seen at later stages of pregnancy. These results demonstrate that the J45 pregnant female phantom series offers the opportunity for significant improvements in both fetal and maternal organ dose assessment within this unique cohort of the atomic bomb survivors.

Journal Articles

Dosimetric impact of a new computational voxel phantom series for the Japanese atomic bomb survivors; Children and adults

Griffin, K.*; Paulbeck, C.*; Bolch, W.*; Cullings, H.*; Egbert, S. D.*; Funamoto, Sachiyo*; Sato, Tatsuhiko; Endo, Akira; Hertel, N.*; Lee, C.*

Radiation Research, 191(4), p.369 - 379, 2019/04

 Times Cited Count:9 Percentile:75.27(Biology)

Due to computing limitations of the time, only three stylized phantoms were used in DS86 and DS02 to represent the entire Japanese population: an infant, child, and adult. Our study aimed to evaluate the dosimetric impact that should be expected from using an updated and age-expanded RERF phantom series with the survivor cohort. To this end, we developed a new series of hybrid phantoms, based on the Japanese population of 1945, which has greater anatomical realism and improved age resolution than those previously used by RERF. From the photon portion of the spectra, dose differences of up to nearly 25% are expected between the old and new series, while differences of up to nearly 70% are expected from the neutron portion. Overall, our new series of phantoms has shown to provide significant improvements to survivor organ dosimetry, especially to those survivors who were previously misrepresented in body size by their stylized phantom and to those who experienced a highly-directional irradiation field.

Journal Articles

The ICRU proposal for new operational quantities for external radiation

Otto, T.*; Hertel, N. E.*; Bartlett, D. T.*; Behrens, R.*; Bordy, J.-M.*; Dietze, G.*; Endo, Akira; Gualdrini, G.*; Pelliccioni, M.*

Radiation Protection Dosimetry, 180(1-4), p.10 - 16, 2018/08

 Times Cited Count:12 Percentile:91.11(Environmental Sciences)

Report Committee 26 of the ICRU proposes a set of operational quantities for radiation protection for external radiation, directly based on effective dose and for an extended range of particles and energies. It is accompanied by new quantities for estimating deterministic effects to the eye lens and the local skin. The operational quantities are designed to overcome the conceptual and technical shortcomings of those presently in use. This paper describes the proposed operational quantities, and highlights the improvements with respect to the present legal monitoring quantities.

Journal Articles

Calculation of fluence-to-effective dose conversion coefficients for the operational quantity proposed by ICRU RC26

Endo, Akira

Radiation Protection Dosimetry, 175(3), p.378 - 387, 2017/07

 Times Cited Count:9 Percentile:79.25(Environmental Sciences)

The International Commission on Radiation Units and Measurements (ICRU) has been discussing to propose a new system of the operational quantities for external radiations based on protection quantities. The aim of this study is to provide a set of conversion coefficients for use in defining personal dose equivalent for individual monitoring. Fluence-to-effective dose conversion coefficients have been calculated for photons, neutrons, electrons, positrons, protons, muons, pions and helium ions for various incident angles of radiations. The data sets comprise effective dose conversion coefficients for incident angles of radiations from 0 $$^{circ}$$ to 90 $$^{circ}$$ in steps of 15$$^{circ}$$ and at 180$$^{circ}$$. Conversion coefficients for rotational, isotropic, superior hemisphere semi-isotropic and inferior hemisphere semi-isotropic irradiations are also included. The conversion coefficients are used to define the operational quantity personal dose equivalent which is being considered by ICRU and utilized for the design and calibration of dosemeters.

Journal Articles

Recent discussion on protection quantities and operational quantities by ICRP and ICRU

Endo, Akira

Hoken Butsuri, 52(1), p.39 - 41, 2017/03

Radiological protection requires the quantification of the extent of exposure of the human body to ionizing radiation. To this end, the International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU) developed a dosimetry system consisting of protection quantities and operational quantities. The existing dosimetry system has been successfully used in radiological protection practice and regulations. Nevertheless, the system has some limitations and needs further improvements to consider changes in the fields of radiological protection. ICRP and ICRU have been discussing the issues to propose an alternative system of radiation dosimetry. This presentation overviews recent discussion on the protection quantities and operational quantities by ICRP and ICRU and the proposed dosimetry system for radiological protection.

Journal Articles

Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd$$_{3}$$(Al,Ga)$$_{5}$$O$$_{12}$$ scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.

Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12

 Times Cited Count:24 Percentile:96.18(Nuclear Science & Technology)

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 4$$times$$4 to 8$$times$$8 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m $$times$$ 60 m and 65 m $$times$$ 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the $$gamma$$-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10$$^{circ}$$).

Journal Articles

Operational quantities and new approach by ICRU

Endo, Akira

Annals of the ICRP, 45(1S), p.178 - 187, 2016/06

The protection quantities, equivalent dose in an organ or tissue and effective dose, were developed by ICRP to allow quantification of the extent of exposure of the human body to ionizing radiation to be used for the implementation of the limitation and optimization principles. The body-related protection quantities are not measurable in practice. Therefore, ICRU developed a set of operational dose quantities for use in radiation measurements for external radiations that provide assessment of the protection quantities. ICRU has examined the rationale for operational quantities taking into account the changes in the definitions of the protection quantities in the ICRP 2007 Recommendations. The committee has investigated a set of alternative definitions for operational quantities different to the existing quantities. The major change in the currently favoured set of quantities is the redefinition of the operational quantities for area monitoring from being based on doses at a point in the ICRU sphere to ones based on particle fluence and the relationship to the protection quantities.

Journal Articles

Summary of ICRP Symposium on Radiological Protection Dosimetry

Endo, Akira; Hamada, Nobuyuki*

Isotope News, (745), p.42 - 43, 2016/06

ICRP Symposium on Radiological Protection Dosimetry was held in Hongo campus, the University of Tokyo on February 18, 2016. Committee 2 of the International Commission on Radiological Protection (ICRP) is engaged in the development of dose coefficients for the assessment of internal and external radiation exposures; development of reference biokinetic and dosimetric models, and reference data for workers and members of the public. The symposium aimed at reviewing the current work of ICRP and discussing research needed for the ICRP System of radiological protection dosimetry. This article reviews the presentations and discussion in the symposium.

Journal Articles

Age-dependent dose conversion coefficients for external exposure to radioactive cesium in soil

Satoh, Daiki; Furuta, Takuya; Takahashi, Fumiaki; Endo, Akira; Lee, C.*; Bolch, W. E.*

Journal of Nuclear Science and Technology, 53(1), p.69 - 81, 2016/01

 Times Cited Count:15 Percentile:89.35(Nuclear Science & Technology)

To estimate effective doses for the public exposed to external radiation from radioactive cesium ($$^{134}$$Cs and $$^{137}$$Cs) deposited on the ground by the Fukushima nuclear accident, we calculate the conversion coefficients for converting activity concentration to effective dose rate by using the Particle and Heavy Ion Transport code System (PHITS). The data were produced from different age groups within the public (newborns; 1-, 5-, 10-, and 15-year-old children; and adults) for the situations in which radioactive cesium is distributed uniformly in the soil over a planar area and at specific depths of 0.0, 0.5, 2.5, 5.0, 10.0, and 50.0 g/cm$$^{2}$$. On the basis of the results, we also derive the conversion coefficients for exponentially distributed volumetric sources. In addition, we obtain the conversion coefficients that give the effective dose accumulated over the first and second months, the first year, and over a lifetime (50 years) because of the contamination remaining on the ground. These calculations indicate that the conversion coefficients to obtain the effective dose rate are higher for the younger ages compared with adults but do not exceed the ambient dose equivalent rate. Furthermore, we find that the difference between the calculated effective dose rates according to the International Commission on Radiological Protection (ICRP) 1990 and 2007 Recommendations is small (7% maximum) for a ground contamination of radioactive cesium.

Journal Articles

Numerical analysis of organ doses delivered during computed tomography examinations using Japanese adult phantoms with the WAZA-ARI dosimetry system

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Ban, Nobuhiko*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Kai, Michiaki*

Health Physics, 109(2), p.104 - 112, 2015/08

 Times Cited Count:8 Percentile:65.81(Environmental Sciences)

A dosimetry system, named WAZA-ARI, is developed to assess accurately radiation doses to persons from Computed Tomography (CT) examination patients in Japan. Organ doses were prepared to application to dose calculations in WAZA-ARI by numerical analyses using average adult Japanese human models with the Particle and Heavy Ion Transport code System (PHITS). Experimental studies clarified the radiation configuration on the table for some multi-detector row CT (MDCT) devices. Then, a source model in PHITS could specifically take into account for emissions of X-ray in each MDCT device based on the experiment results. Numerical analyses with PHITS revealed a concordance of organ doses with human body size. The organ doses by the JM phantoms were compared with data obtained using previously developed systems. In addition, the dose calculation in WAZA-ARI were verified with previously reported results by realistic NUBAS phantoms and radiation dose measurement using a physical Japanese model. The results implied that analyses using the Japanese phantoms and PHITS including source models can appropriately give organ dose data with consideration of the MDCT device and physiques of typical Japanese adults.

Journal Articles

ICRP Publication 116 "Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures"; Summary

Endo, Akira

Isotope News, (736), p.34 - 37, 2015/08

Japanese translation of ICRP Publication 116 entitled "Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures" was published by the Japan Radioisotope Association in March 2015. The book gives fluence to dose conversion coefficients for both effective dose and organ absorbed doses for various types of external exposures, consistent with the 2007 Recommendations of the ICRP. A complete set of conversion coefficients is provided in an accompanying CD in ASCII format and Microsoft Excel software. This article overviews ICRP Publication 116 and its impact to practice of radiation protection.

Journal Articles

WAZA-ARI; A Dose assessment system for patients in CT scan

Sato, Kaoru; Takahashi, Fumiaki; Endo, Akira; Ono, Koji*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

RIST News, (58), p.25 - 32, 2015/01

The Japan Atomic Energy Agency (JAEA) are now developing WAZA-ARI for improvement of management of exposure doses due to CT examination under the joint research with the Oita University of Nursing and Health Sciences. The trial version of WAZA-ARI has been released on 21 December 2012. In trial version, users can perform dose assessment by using organ dose database based on the average adult Japanese male (JM-103) and female (JF-103) voxel phantoms and a 4 years old female voxel phantom (UFF4). The homepage of WAZA-ARI has been accessed over 1000 times per month and 28421 times by the end of September 2014. We are developing WAZA-ARI version 2 as the extension version of dose calculation functions of WAZA-ARI. WAZA-ARI version 2 will be released by the end of March 2015. In WAZA-ARI version 2. Users can upload dose calculation results to WAZA-ARI version 2 server, and utilize improvement of the dose management of patients and the optimization of CT scan conditions.

Journal Articles

Measurements and evaluations of air dose rates around Fukushima, 3; Characteristics of environmental $$gamma$$ rays and the exposure doses

Saito, Kimiaki; Endo, Akira

Radioisotopes, 63(12), p.585 - 602, 2014/12

The article provides the fundamental information necessary for the appropriate evaluation of exposure doses in the environment. The basic characteristics of environmental $$gamma$$ rays from typical environmental sources are introduced; then, the dose conversion coeffcients for the public at different ages are summarized which were obtained from the simulation considering the basic characteristics of environmental $$gamma$$ rays. Further, the variations of environmental exposure doses due to a variety of factors, and the relation of exposure doses to measured air dose rates are discussed.

Journal Articles

Overview of the ICRP/ICRU adult reference computational phantoms and dose conversion coefficients for external idealised exposures

Endo, Akira; Petoussi-Henss, N.*; Zankl, M.*; Bolch, W. E.*; Eckerman, K. F.*; Hertel, N. E.*; Hunt, J. G.*; Pelliccioni, M.*; Schlattl, H.*; Menzel, H.-G.*

Radiation Protection Dosimetry, 161(1-4), p.11 - 16, 2014/10

 Times Cited Count:2 Percentile:19.81(Environmental Sciences)

In 2007, the International Commission on Radiological Protection (ICRP) revised its fundamental recommendations on radiation protection in ICRP Publication 103 (ICRP103). The recommendations updated the radiation and tissue weighting factors in the radiological protection quantities, equivalent and effective doses, and adopted reference computational phantoms for the calculation of organ doses. These revisions required calculations of conversion coefficients for the protection quantities. The sets of conversion coefficients for external exposures were compiled by the Task Group DOCAL of ICRP, and published in ICRP116. The presentation reviews the conversion coefficients for external radiations calculated using the reference computational phantoms. The conversion coefficients are compared with the existing values given in ICRP74. Contributing factors for any differences between these sets of conversion coefficients as well as the impact for radiation monitoring practice are discussed.

Journal Articles

ICRP Publication 116; The First ICRP/ICRU application of the male and female adult reference computational phantoms

Petoussi-Henss, N.*; Bolch, W. E.*; Eckerman, K. F.*; Endo, Akira; Hertel, N.*; Hunt, J.*; Menzel, H. G.*; Pelliccioni, M.*; Schlattl, H.*; Zankl, M.*

Physics in Medicine & Biology, 59(18), p.5209 - 5224, 2014/09

 Times Cited Count:3 Percentile:20.03(Engineering, Biomedical)

ICRP Publication 116 (ICRP116) on "Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures", provides fluence-to-dose conversion coefficients for organ absorbed doses and effective dose for external exposures. ICRP116 supersedes the ICRP74, expanding also the particle types and energy ranges considered. The coefficients were calculated using the ICRP/ICRU computational phantoms representing the Reference Adult Male and Reference Adult Female, together with Monte Carlo codes simulating the radiation transport in the body. Idealised whole-body irradiation from unidirectional and rotational parallel beams as well as isotropic irradiation was considered. Comparison of the effective doses with operational quantities revealed that the latter quantities continue to provide a good approximation of effective dose for photons, neutrons and electrons for the conventional energy ranges considered previously, but not at the higher energies of ICRP116.

JAEA Reports

Calculation of dose conversion coefficients for external exposure to radioactive cesium distributed in soil

Satoh, Daiki; Furuta, Takuya; Takahashi, Fumiaki; Endo, Akira; Lee, C.*; Bolch, W. E.*

JAEA-Research 2014-017, 25 Pages, 2014/08


In order to estimate effective dose for the public for external exposure to radioactive cesium distributed in a soil due to the accident of the Fukushima Daiichi Nuclear Power Station, dose conversion coefficients (DCC) have been calculated by using a three-dimensional radiation transport code PHITS. The DCC were evaluated for different ages constituting the public, that is 6-day-old babies, 1-, 5-, 10-, and 15-year-old children, and adults, under the condition which the radioactive cesiums, Cs-134 and Cs-137, are distributed uniformly in the soil with a specific depth of 0.0 g/cm$$^{2}$$, 0.5 g/cm$$^{2}$$, 2.5 g/cm$$^{2}$$, 5.0 g/cm$$^{2}$$, and 10.0 g/cm$$^{2}$$. In addition, we evaluate the DCC for cumulative effective dose for external exposure by remaining on ground with radioactive cesium for a period of concern, that is 1 month, 1 year, and 50 years. As a result of the calculation, it was found that the effective dose for any age does not exceed the value of ambient dose equivalent H$$^{*}$$(10), while the effective dose increases with decreasing the age, and the difference of dosimetry system between the ICRP 1990 and 2007 Recommendations does not make a significant difference for the external dose calculation on contaminated ground. We also developed a method to evaluate the DCC for volume source with an arbitrary distribution in a soil, and derived an equation to be applicable to dose estimation in contaminated areas around Fukushima Daiichi Nuclear Power Station considering initial condition of radioactivity of Cs-134 and Cs-137.

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