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Journal Articles

Application of voxel phantoms and Monte Carlo method to whole-body counter calibrations

Kinase, Sakae; Takagi, Shunji*; Noguchi, Hiroshi; Saito, Kimiaki

Radiation Protection Dosimetry, 125(1-4), p.189 - 193, 2007/07

 Times Cited Count:16 Percentile:74.03(Environmental Sciences)

In the Japan Atomic Energy Research Institute (JAERI), a calculation code -UCWBC code- for whole-body counter calibrations using voxel phantoms has been developed as an EGS4 Monte Carlo user code. To validate the UCWBC code for calibrating whole-body counters in JAERI, response functions and counting efficiencies of a p-type high-purity Ge semiconductor detector used for the whole-body counter were evaluated for a water-filled block-shape phantom by the UCWBC code and were measured by experiments. Furthermore, counting efficiencies of the Ge semiconductor detector for the male and female voxel phantoms developed in JAERI were evaluated in the photon energy range 60-1836 keV by the UCWBC code in order to examine the differences between the counting efficiencies for voxel phantoms. In conclusion, it was found that the response functions and counting efficiencies of the Ge semiconductor detector by the UCWBC code for the water-filled block-shape phantom are in good agreement with measured data. The UCWBC code was validated by the comparisons.

Journal Articles

Application of EGS4 code to evaluation of specific absorbed fractions and S values for internal dosimetry

Kinase, Sakae

KEK Proceedings 2005-3, p.292 - 297, 2005/06

The EGS4 code was used for evaluating the absorbed fraction per unit mass of the target organ-specific absorbed fraction (SAF)- and the mean absorbed dose to the target organ per unit cumulated activity in the source organ (S value) for internal dosimetry. The SAFs and S values were evaluated on a mathematical phantom (MIRD 5 type phantom) and Japanese adult voxel phantoms (Otoko and Onago phantoms) developed at the Japan Atomic Energy Research Institute (JAERI). The evaluated SAFs and S values were compared with several published data in order to demonstrate the use of the EGS4 code for the internal dosimetry and investigate the influence of certain parameters, such as the organ masses, on SAFs and S values. It was demonstrated that the EGS4 code is useful in the evaluation of the SAFs and S values for the internal dosimetry. It was also found that the SAFs and S values for organ self-absorption depend on the organ masses and would be affected by differences in the structure of the human body.

Journal Articles

Evaluation of counting efficiency of whole-body counter using voxel phantoms

Kinase, Sakae; Takagi, Shunji*; Noguchi, Hiroshi; Saito, Kimiaki

Proceedings of 11th International Congress of the International Radiation Protection Association (IRPA-11) (CD-ROM), 7 Pages, 2004/05

The present study was performed to validate the UCWBC code for calibrating in vivo measurements. Furthermore, the calibration data for the adult voxel phantoms developed in JAERI were evaluated by the UCWBC code in order to examine the differences between the calibration data for voxel phantoms, including a voxel version of water-filled block-shape phantom based on an actual phantom that is used for the calibration of the whole-body counter in JAERI. It was found that the calculated calibration data by the UCWBC code for the water-filled block-shape phantom show good agreement with measured ones. Consequently, the UCWBC code was validated by the comparisons. It was also found that the calibration data depend on phantoms of different sizes and the effective distance between phantom and detector. The calibration of in vivo measurements using voxel phantoms for individuals would be quite useful for the improvement in accuracy of the measurement results.

Journal Articles

Evaluation of S values for beta-ray emitters in voxel phantoms

Kinase, Sakae; Zankl, M.*; Funabiki, Jun*; Noguchi, Hiroshi; Saito, Kimiaki

KEK Proceedings 2003-15, p.45 - 52, 2004/02

no abstracts in English

Journal Articles

Evaluation of specific absorption fractions in voxel phantoms using Monte Carlo simulation

Kinase, Sakae; Zankl, M.*; Kuwabara, Jun; Sato, Kaoru; Noguchi, Hiroshi; Funabiki, Jun*; Saito, Kimiaki

Radiation Protection Dosimetry, 105(1-4), p.557 - 563, 2003/09

 Times Cited Count:26 Percentile:84.61(Environmental Sciences)

There exists a need to calculate specific absorbed fractions (SAFs) in voxel phantoms for internal dosimetry. For this purpose, an EGS4 user code for calculating SAFs using voxel phantoms was developed on the basis of an existing EGS4 user code for external dosimetry (UCPIXEL). In the developed code, the transport of photons, electrons and positrons in voxel phantoms can be simulated, particularly the transport simulations of secondary electrons in voxel phantoms can be made. The evaluated SAFs for the GSF Child voxel phantom using the developed code were found to be in good agreement with the GSF evaluated data. In addition, SAFs in adult voxel phantoms developed at JAERI were evaluated using the developed code and were compared with several published data. It was found that SAFs for organ self-absorption depend on the organ masses and would be affected by differences in the structure of the human body.

Journal Articles

Analyses of absorbed dose to tooth enamel against external photon exposure

Takahashi, Fumiaki; Yamaguchi, Yasuhiro; Iwasaki, Midori*; Miyazawa, Chuzo*; Hamada, Tatsuji*; Funabiki, Jun*; Saito, Kimiaki

Radiation Protection Dosimetry, 103(2), p.125 - 130, 2003/01

 Times Cited Count:4 Percentile:32.21(Environmental Sciences)

Absorbed dose to tooth enamels against external photon exposure was examined by the Electron Spin Resonance (ESR) dosimetry using tooth samples placed in a realistic physical phantom. Dose to teeth region was also measured with thermo-luminescence dosimeters (TLDs). A voxel-type phantom was constructed from CT images of the physical phantom. Monte Carlo calculations with this voxel-type phantom were performed to analyse the results of the experiments. The obtained data in this study were compared to the enamel doses, which were calculated with a modified MIRD-type and already given in a previous paper. The results suggested that the conversion factors from enamel dose to organ doses obtained by the modified MIRD-type phantom are to be applicable for retrospective individual dose assessments by the ESR dosimetry. The analysis, however, indicated that the size and figure of the head can affect the enamel dose for low photon energy region below 100keV.

Journal Articles

Construction of a computed tomographic phantom for a Japanese male adult and dose calculation system

Saito, Kimiaki; Wittmann, A.*; Koga, Sukehiko*; Ida, Yoshihiro*; Kamei, Tetsuya*; Funabiki, Jun*; Zankl, M.*

Radiation and Environmental Biophysics, 40(1), p.69 - 76, 2001/04

 Times Cited Count:90 Percentile:90.4(Biology)

no abstracts in English

Journal Articles

Evaluation of specific absorbed fractions in voxel phantoms using Monte Carlo simulation

Kinase, Sakae; Zankl, M.*; Kuwabara, Jun; Sato, Kaoru; Noguchi, Hiroshi; Funabiki, Jun*; Saito, Kimiaki

Radiation Risk Assessment Workshop Proceedings, p.118 - 127, 2001/00

There exists a need to calculate specific absorbed fractions (SAFs) in voxel phantoms for internal dosimetry. For the purpose, an EGS4 user code for calculating SAFs using voxel phantoms was developed on the basis of the EGS4 user code (UCPIXEL). In the developed code, the transport of photons, electrons and positrons in voxel phantoms can be simulated, particularly the transport simulations of secondary electrons in voxel phantoms can be made. The evaluated SAFs for the GSF "Child" voxel phantom using the developed code were found to be in good agreement with the GSF evaluated data. In addition, SAFs in voxel phantoms developed at JAERI were evaluated using the developed code and were compared with several published data. It was found that SAFs depend on the organ masses and would be affected by differences in the structure of the human body.

Journal Articles

Development of CT voxel phantoms for Japanese

Sato, Kaoru; Noguchi, Hiroshi; Saito, Kimiaki; Emoto, Yutaka*; Koga, Sukehiko*

Radiation Risk Assessment Workshop Proceedings, p.102 - 110, 2001/00

For calculating doses due to radioactivity taken in a body, Specific Absorbed Fractions (SAFs) are used. In recent years, more realistic phantoms called voxel (volume pixel) phantoms have been developed on the basis of CT or MRI images of actual persons. The voxel phantoms can accurately describe sizes, shapes and locations of organs, which would affect SAFs. We are now developing Japanese adult voxel phantoms for internal dosimetry by using CT images. Until now, CT scans for three healthy Japanese male volunteers were performed under supine or upright positions to study the effect of body size and position on SAFs. The height and weight of the middle size man is almost coincident with the averages for Japanese adult. So far the development of voxel phantom has been almost finished for the middle size man (voxel-phantom-MM). The voxel size is 0.98$$times$$0.98$$times$$1.0 mm$$^{3}$$. It was found that even small size organs such as thyroid were realistically modeled. The result showed that voxel-phantom-MM had realistic structure which would enable us to calculate reliable SAFs

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

Developments toward radiation dose assessment using next generation polygon human phantoms

Furuta, Takuya; Sato, Kaoru; Takahashi, Fumiaki

no journal, , 

Voxel-based computational human phantoms have been used for radiation dose assessment with Monte Carlo radiation transport simulation codes. However, development of polygon-based computation humans becomes popular due to advantages on description of thin layer tissues and small organs. International Commission on Radiological Protection (ICRP) also announced to adopt polygon human phantoms as the reference phantoms. We therefore introduced a function to treat tetrahedral-mesh geometry, a type of polygon geometry, into Particle and Heavy Ion Transport code Systems (PHITS). Along this implementation, we also developed an efficient transport algorithm with tetrahedral-mesh geometry, which allows to reduce the computational time to 1/4 of the voxel-mesh calculation using the same precision computational human phantom. We also started a development of new polygon-based human phantoms based on Japanese voxel phantoms. The complete version will be published hopefully next year.

Oral presentation

Performance of voxel and mesh phantoms in PHITS

Furuta, Takuya

no journal, , 

Recently polygon phantoms with tetrahedral-mesh became treatable in PHITS by implementation of a new function. Using this function, radiation transport simulation of external radiation exposure of the new ICRP mesh-type reference computational phantoms becomes possible. The function was introduced together with an original algorithm to limit number of elements and surfaces in search during the transport calculation to reduce the computational cost. Owing to this algorithm, efficient transport calculation in tetrahedral-mesh geometries was realized as good as in voxel-mesh geometries with the same number of meshes. The tetrahedral-mesh can represent complex structures such as human phantoms with a much smaller number of meshes compared to the voxel representation and thus the computational speeds of radiation transport simulation using human phantoms can be faster with tetrahedral-mesh representation. The performance of PHITS was demonstrated by a comparison of the computational time between the voxel and tetrahedral-mesh for radiation transport calculations in water and human phantoms. Benchmark studies using the ICRP mesh-type reference computational phantoms in comparison with other Monte Carlo codes such as MCNP and Geant4 were also performed.

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