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Journal Articles

PARaDIM; A PHITS-based Monte Carlo tool for internal dosimetry with tetrahedral mesh computational phantoms

Carter, L. M.*; Crawford, T. M.*; Sato, Tatsuhiko; Furuta, Takuya; Choi, C.*; Kim, C. H.*; Brown, J. L.*; Bolch, W. E.*; Zanzonico, P. B.*; Lewis, J. S.*

Journal of Nuclear Medicine, 60(12), p.1802 - 1811, 2019/12

 Times Cited Count:2 Percentile:55.17(Radiology, Nuclear Medicine & Medical Imaging)

Voxel human phantoms have been used for internal dose assessment. More anatomically accurate representation become possible for skins or layer tissues owing to recent developments of advanced polygonal mesh-type phantoms and thus internal dose assessment using those advanced phantoms are desired. However, the Monte Carlo transport calculation by implementing those phantoms require an advanced knowledge for the Monte Carlo transport codes and it is only limited to experts. We therefore developed a tool, PARaDIM, which enables users to conduct internal dose calculation with PHITS easily by themselves. With this tool, a user can select tetrahedral-mesh phantoms, set radionuclides in organs, and execute radiation transport calculation with PHITS. Several test cases of internal dosimetry calculations were presented and usefulness of this tool was demonstrated.

Journal Articles

Organ and detriment-weighted dose rate coefficients for exposure to radionuclide-contaminated soil considering body morphometries that differ from reference conditions; Adults and children

Kofler, C.*; Domal, S.*; Satoh, Daiki; Dewji, S.*; Eckerman, K.*; Bolch, W. E.*

Radiation and Environmental Biophysics, 58(4), p.477 - 492, 2019/11

 Times Cited Count:0 Percentile:100(Biology)

In the current radiation protection system, the International Commission on Radiological Protection (ICRP) recommends to use the effective dose for dose estimation. The effective dose is derived from the organ doses calculated using the computational human models (phantoms) defined by the ICRP to represent the reference person at each age. Questions arise, however, among the general public regarding the accuracy of organ and effective dose estimates based upon reference phantom methodologies, especially for those individuals with heights and/or weights that differ from the nearest age-matched reference person. In this paper, the detriment-weighted dose was defined for non-reference persons as the same manner to the effective dose for reference person. The doses were calculated for external exposure to radionuclides in a soil using 351-member phantom library based on the data of the U.S. population reported by the U.S. National Center for Health Statistics. The results for 33 nuclides were listed in the paper. Especially, for the environmental relevant radionuclides of $$^{89}$$Sr, $$^{90}$$Sr, $$^{137}$$Cs, and $$^{131}$$I, the detriment-weighted dose of 1-year-old phantom agreed with the effective dose within 5%, while the range of percent differences in these two quantities increased with increases the body size and age, e.g. +15% to -40% for adults.

Journal Articles

Dosimetric dependence of ocular structures on eye size and shape for external radiation fields of electrons, photons, and neutrons

Furuta, Takuya; El Basha, D.*; Iyer, S. S. R.*; Correa Alfonso, C. M.*; Bolch, W. E.*

Journal of Radiological Protection, 39(3), p.825 - 837, 2019/09

 Times Cited Count:0 Percentile:100(Environmental Sciences)

Despite large variation of human eye, only one computational eye model has been adopted in almost all the radiation transport simulation studies. We thus adopted a new scalable and deformable eye model and studied the radiation exposure by electrons, photons, and neutrons in the standard radiation fields such as AP, PA, RLAT, ROT, by using Monte Carlo radiation transport code PHITS. We computed the radiation exposure for 5 eye models (standard, large, small, myopic, hyperopic) and analyzed influence of absorbed dose in ocular structures on eye size and shape. Dose distribution of electrons is conformal and therefore the absorbed doses in ocular structures depend on the depth location of each ocular structure. We thus found a significant variation of the absorbed doses for each ocular structure for electron exposure due to change of the depth location affected by eye size and shape. On the other hand only small variation was observed for photons and neutrons exposures because of less conformal dose distribution of those particles.

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:0 Percentile:100(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

A Scalable and deformable stylized model of the adult human eye for radiation dose assessment

El Basha, D.*; Furuta, Takuya; Iyer, S. S. R.*; Bolch, W. E.*

Physics in Medicine and Biology, 63(10), p.105017_1 - 105017_13, 2018/05

 Times Cited Count:3 Percentile:48.33(Engineering, Biomedical)

With recent changes in the recommended annual limit on eye lens exposures to ionizing radiation by International Commission on Radiological Protection, there is considerable interest in predictive computational dosimetry models of the human eye and its various ocular structures. Several computational eye models to date have been constructed for this purpose but they are typically constructed of nominal size and of a roughly spherical shape associated with the emmetropic eye. We therefore constructed a geometric eye model that is both scalable (allowing for changes in eye size) and deformable (allowing for changes in eye shape), and that is suitable for use in radiation transport studies of ocular exposures and radiation treatments of eye disease. As an example, electron and photon anterior-posterior radiation transport with the constructed eye model was conducted and analyzed resultant energy-dependent dose profiles. Due to anterior-posterior irradiation, the energy dose response was shifted to higher energy for a larger-size eye or an axially deformed eye in prolate shape because the structures were located in deeper depth compared to the normal eye.

Journal Articles

Simulation study of personal dose equivalent for external exposure to radioactive cesium distributed in soil

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

Journal of Nuclear Science and Technology, 54(9), p.1018 - 1027, 2017/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The personal dose equivalent was calculated for the public (newborns; 1-, 5-, 10-, and 15-year-old children; and adults) in an environment contaminated with radioactive cesium ($$^{134}$$Cs and $$^{137}$$Cs) distributed in a soil at specific depths of 0.0, 0.5, 2.5, 5.0, 10.0, and 50.0 g/cm$$^2$$. Monte Carlo calculations were performed using pediatric and adult computational phantoms incorporated into a particle and heavy ion transport code system (PHITS). Compared with the effective dose and ambient dose equivalent at a height of 100 cm above the ground, the personal dose equivalent was found to provide an acceptable assessment for the effective dose and did not exceed the ambient dose equivalent in the environmental radiation field, while the personal dose equivalent values increased for younger subjects. The weighted-integral method to obtain the personal dose equivalent for a volumetric source was applied to the analysis of exponential radioactive cesium distributions in the soil observed in Fukushima, and the calculation results successfully reproduced the measured data.

Journal Articles

Implementation of tetrahedral-mesh geometry in Monte Carlo radiation transport code PHITS

Furuta, Takuya; Sato, Tatsuhiko; Han, M. C.*; Yeom, Y. S.*; Kim, C. H.*; Brown, J. L.*; Bolch, W. E.*

Physics in Medicine and Biology, 62(12), p.4798 - 4810, 2017/06

 Times Cited Count:6 Percentile:40.64(Engineering, Biomedical)

A new function to treat tetrahedral-mesh geometry, a type of polygon-mesh geometry, was implemented in the Particle and Heavy Ion Transport code Systems (PHITS). Tetrahedral-mesh is suitable to describe complex geometry including curving shapes. In addition, construction of three-dimensional geometry using CAD software becomes possible with file format conversion. We have introduced a function to create decomposition maps of tetrahedral-mesh objects at the initial process so that the computational time for transport process can be reduced. Owing to this function, transport calculation in tetrahedral-mesh geometry can be as fast as that for the geometry in voxel-mesh with the same number of meshes. Due to adaptability of tetrahedrons in size and shape, dosimetrically equivalent objects can be represented by tetrahedrons with much fewer number of meshes compared with the voxels. For dosimetric calculation using computational human phantom, significant acceleration of the computational speed, about 4 times, was confirmed by adopting the tetrahedral mesh instead of the voxel.

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:12 Percentile:11.43(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

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:77.15(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 and Biology, 59(18), p.5209 - 5224, 2014/09

 Times Cited Count:2 Percentile:82.57(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

JAEA-Research-2014-017.pdf:15.8MB

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.

Journal Articles

A Comparative study of space radiation organ doses and associated cancer risks using PHITS and HZETRN

Bahadori, A. A.*; Sato, Tatsuhiko; Slaba, T. C.*; Shavers, M. R.*; Semones, E. J.*; Baalen, M. V.*; Bolch, W. E.*

Physics in Medicine and Biology, 58(20), p.7183 - 7207, 2013/10

 Times Cited Count:5 Percentile:70.69(Engineering, Biomedical)

In the present study, organ absorbed doses and dose equivalents are calculated for 50th percentile male and female astronaut phantoms using both the NASA High Charge and Energy Transport Code (HZETRN) to perform one-dimensional deterministic transport and using the Particle and Heavy Ion Transport code System (PHITS) to perform three-dimensional Monte Carlo transport. Code-to-code benchmarks allow for the comparison of differential quantities, such as secondary particle differential fluence, to provide insight into differences observed in integral quantities for particular components of the GCR spectrum.

Oral presentation

WAZA-ARI2; Web-based CT dose calculator for Asian physiques

Ono, Koji*; Sato, Kaoru; Takahashi, Fumiaki; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Kamei, Osamu*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Endo, Akira; Lee, C.*; et al.

no journal, , 

We developed a web-based CT dosimetry system, WAZA-ARI, which calculates doses to average-sized Japanese adults (male and female) as well as a four-year-old girl. The system is being upgraded to a new version, WAZA-ARI 2, incorporating several new features. To enable the dose calculation for a wider range of subjects, WAZA-ARI 2 utilizes voxelized hybrid phantoms developed by Florida University (0, 1, 5, 10 and 15 years old, both sexes) in addition to the JAEA voxel phantoms of the average-sized Japanese male and female. It is also capable of calculating doses to adults with small, large and extra-large body sizes. The system computes tissue doses on user's request referring to the dose coefficient datasets that have been calculated using the Particle and Heavy Ion Transport code System (PHITS). As the phantoms used represent physiques of Asian population, WAZA-ARI 2 is appropriate to calculate patient doses in Asian countries.

Oral presentation

ICRP activities on dose coefficients for members of the public from external exposures to environmental sources

Petoussi-Henss, N.*; Bellamy, M.*; Bolch, W. E.*; Eckerman, K. F.*; Endo, Akira; Hertel, N.*; Hunt, J.*; Jansen, J.*; Kim, C. H.*; Lee, C.*; et al.

no journal, , 

A Task Group of the Committee 2 of the International Commission on Radiological Protection, ICRP, is currently working on the estimation of effective dose and organ dose coefficients for members of the public due to environmental external exposures to photons and electrons. The JAEA is contributing to the Task Group by calculating the doses with the radiation transport code PHITS which has been developed in the JAEA. Those calculations were performed using the ICRP adult and pediatric male and female reference computational phantoms for the environmental radiation sources in air, soil, and water. The obtained results of effective dose and organ dose are normalized to radioactivity concentration, ambient dose equivalent, and air kerma, and summarize in a database of the dose coefficients. Furthermore, dose coefficients for radionuclides in the environment are also evaluated by using the most recent nuclear decay data.

Oral presentation

A Simulation study of personal dose equivalent for external exposure to radioactive cesium distributed in soil

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

no journal, , 

In the guidance to return to the areas where the evacuation orders have been lifted, the Nuclear Regulation Authority made a statement that the radiation dose of returnees should be assessed based on individual monitoring instead of spatial monitoring with the ambient dose equivalent. The individual monitoring of external exposure is usually performed with a personal dosimeter worn on a body, and the dosimeter indicate a personal dose equivalent Hp(10). Hence, the relationship of the personal dose equivalent to the ambient dose equivalent and the effective dose in the environment contaminated with the radioactive cesium must be quantified to control the radiation exposure of the residents. In the present work, the age-dependent personal dose equivalent is analyzed for the radioactive cesium distributing in soil at a depth of 0.0, 0.5, 2.5, 10.0, and 50.0 g/cm$${^2}$$ by means of the radiation transport code PHITS and the computational phantoms representing the newborn; 1-year old, 5-year old, 10-year old, and 15 year old children, and adults. From the results, it was found that the personal dose equivalent provides an acceptable assessment for the effective dose, and does not exceed the ambient dose equivalent in the contaminated environment.

Oral presentation

A Computational method for voxel to polygon mesh conversion of anatomic computational human phantoms

Brown, J. L.*; Furuta, Takuya; Bolch, W. E.*

no journal, , 

Computational human phantoms in a voxelized format have been used in radiation dose assessments with Monte Carlo radiation transport codes. Recently, the transport in human computational phantoms represented by polygon mesh structure becomes possible with the several Monte Carlo codes. Individual organs and body circumferences are better represented by mesh-type human phantom than by voxel-based phantoms. Tremendous number of voxel-based phantoms have been developed from CT or MR data, and thus there is a need for conversion of existing models to mesh-type formats to allow this additional benefit. We therefore developed an algorithm which accurately converts computational voxelized human phantoms into a polygon-mesh format by detecting boundaries of individual organs. The converted polygon-mesh phantoms can be visualized using CAD software as well as they can be used for radiation transport calculation in Monte Carlo codes.

Oral presentation

Development of a scalable and deformable stylized eye model and its application to the standard radiation exposure geometries

Furuta, Takuya; El Basha, D.*; Iyer, S. S. R.*; Correa Alfonso, C. M.*; Bolch, W. E.*

no journal, , 

With recent changes in the recommended annual dose limit on eye lens by International Commission on Radiological Protection, there is considerable interest in assessment of radiation exposure on eyes. Several Monte Carlo studies has been performed using a computational eye model. Although there are a large variety in size and shape for individual eyes, the eye model of one standard eye size and shape was adopted in most of those studies. We therefore constructed a geometric eye model that is both scalable (allowing for changes in eye size) and deformable (allowing for changes in eye shape), and studied dosimetry influence on the variation of the eye size and shape in the standard ICRP radiation geometries. We confirmed that only a trivial dependence on the eye size and shape, namely variation of the depth location of the ocular structures, was observed for radiation exposure in the broad radiation geometries.

Oral presentation

Development of a scalable and deformable stylized eye model for radiation dose assessment

Furuta, Takuya; El Basha, D.*; Iyer, S. S. R.*; Correa Alfonso, C. M.*; Bolch, W. E.*

no journal, , 

With recent changes in the recommended annual dose limit on eye lens by International Commission on Radiological Protection, several Monte Carlo studies has been performed using a computational eye model. Although there are a large variety in size and shape for individual eyes, the eye model of one standard eye size and shape was adopted in most of those studies. We therefore constructed a geometric eye model that is both scalable and deformable, and studied dosimetry influence on the variation of the eye size and shape in the standard radiation geometries using Monte Carlo radiation transport code PHITS. We confirmed that only a trivial dependence on the eye size and shape, namely variation of the depth location of the ocular structures, was observed for radiation exposure in the broad radiation geometries.

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