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Furuta, Takuya; Sato, Tatsuhiko; Han, M. C.*; Yeom, Y. S.*; Kim, C. H.*; Brown, J. L.*; Bolch, W. E.*
Physics in Medicine & Biology, 62(12), p.4798 - 4810, 2017/06
Times Cited Count：10 Percentile：47.17(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.
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.
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.
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.
