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Furuta, Takuya; Koba, Yusuke*; Hashimoto, Shintaro; Chang, W.*; Yonai, Shunsuke*; Matsumoto, Shinnosuke*; Ishikawa, Akihisa*; Sato, Tatsuhiko
Physics in Medicine & Biology, 67(14), p.145002_1 - 145002_15, 2022/07
Times Cited Count：2 Percentile：47.19(Engineering, Biomedical)Carbon ion radiotherapy has an advantage over conventional radiotherapy such that its superior dose concentration on the tumor helps to reduce unwanted dose to surrounding normal tissues. Nevertheless, a little dose to normal tissues, which is a potential risk of secondary cancer, is still unavoidable. The Monte Carlo simulation is a good candidate for the tool to assess secondary cancer risk, including the contributions of secondary particles produced by nuclear reactions. We therefore developed a new dose reconstruction system implementing PHITS as the engine. In this system, the PHITS input is automatically created from the DICOM data sets recorded in the treatment planning. The developed system was validated by comparing to experimental dose distribution in water and treatment plan on an anthropomorphic phantom. This system will be used for retrospective studies using the patient data in National Institute for Quantum and Science and Technology.
Chang, W.*; Koba, Yusuke*; Furuta, Takuya; Yonai, Shunsuke*; Hashimoto, Shintaro; Matsumoto, Shinnosuke*; Sato, Tatsuhiko
Journal of Radiation Research (Internet), 62(5), p.846 - 855, 2021/09
Times Cited Count：2 Percentile：26.61(Biology)With the aim of developing a revaluation tool of treatment plan in carbon-ion radiotherapy using Monte Carlo (MC) simulation, we propose two methods; one is dedicated to identify realistic-tissue materials from a CT image with satisfying the well-calibrated relationship between CT numbers and stopping power ratio (SPR) provided by TPS, and the other is to estimate dose to water considering the particle- and energy-dependent SPR between realistic tissue materials and water. We validated these proposed methods by computing depth dose distribution in homogeneous and heterogeneous phantoms composed of human tissue materials and water irradiated by a 400 MeV/u carbon beam with 8 cm SOBP using a MC simulation code PHITS and comparing with results of conventional treatment planning system (TPS). Our result suggested that use of water as a surrogate of real tissue materials, which is adopted in conventional TPS, is inadequate for dose estimation from secondary particles because their production rates cannot be scaled by SPR of the primary particle in water. We therefore concluded that the proposed methods can play important roles in the reevaluation of the treatment plans in carbon-ion radiotherapy.
Tahara, Yoshihisa*; Abe, Shinji*; Yonai, Shunsuke*; Baba, Mamoru*; Unno, Yasuhiro*; Sasa, Toshinobu; Iwanaga, Kohei; Yokobori, Hitoshi*; Tsutsui, Takehiko*; Kamei, Yoshihide*
no journal, ,
To realize the boron neutron capture therapy, the existence of the method using the 400 MeV proton beam, which is planned to supply the J-PARC transmutation experimental facility, are studied. As the preliminary examination, a method to obtain epithermal neutron using neutrons which generated by Ta target bonbarded by 400 MeV protons and moderated with iron and fluental moderators. To suppress the unexpected exposure, lead reflector is located around the target and moderators. By the preliminary analysis using MCNPX code and LA150 cross section library, the beam current about 5 micro ampere are enough for effective for brain-canther treatment.
Tahara, Yoshihisa*; Abe, Shinji*; Sasa, Toshinobu; Yonai, Shunsuke*; Baba, Mamoru*; Yokobori, Hitoshi*
no journal, ,
Conceptual study of the epithermal neutron source for BNCT by the bomberdment of 400 MeV proton which is planned to supply at Japan proton accelerator research complex, J-PARC. The neutron source, which has two neutron extraction port, is designed to obtain epithermal neutron source by the moderation of spallation neutron source from tungsten target using iron and fluental moderator. By the analytical result of the radiation dose in human phantom located at the exit of exposure port, about 60 minutes of irradiation time is obtained by the injection of 5 micro ampere protons. It is shown that this spallation neutron source is applicable to the epithermal neutron source for BNCT.
Furuta, Takuya; Koba, Yusuke*; Chang, W.*; Hashimoto, Shintaro; Yonai, Shunsuke*; Matsumoto, Shinnosuke*; Sato, Tatsuhiko
no journal, ,
Heavy-ion (carbon-ion) therapy has advantages over conventional radiotherapy such as superior dose concentration and better relative biological effectiveness while the secondary particles produced by nuclear reactions between incident carbon ions and matters induce complexity for risk assessment of secondary cancer. For this assessment, precise transport calculation of secondary particles are required so the Monte Carlo transport calculation is desired. We therefore construct a dosimetry system including PHITS as the engine. In this system, the PHITS input is automatically created from the DICOM data sets recorded in the treatment planning. The transport calculation is simulated by PHITS and dose distribution around the tumor but also out-of-filed is computed. This system will be used as retrospective study in National Institute of Radiological Sciences.
Chang, W.*; Koba, Yusuke*; Furuta, Takuya; Yonai, Shunsuke*; Hashimoto, Shintaro; Matsumoto, Shinnosuke*; Sato, Tatsuhiko
no journal, ,
In the treatment planning system (TPS) for radiotherapy, approximate calculation by replacing all materials with water and accounting only the density variation is adopted to reduce the computational cost. On the other hand, conversion from patient CT data to elemental compositions and densities is required to conduct Monte Carlo simulation. Especially for the assessment of secondary cancer risk in carbon therapy, secondary particles produced in the nuclear reaction between incident carbons and human tissues are important so that the difference of the elemental compositions is essential. We have therefore developed a method to convert CT number to human tissues keeping the consistency with the water stopping power table embedded in TPS. We applied this conversion method to 9 different human tissues and confirmed the range of carbon beams are reproduced within 1 mm precision for all the materials.
Ishikawa, Akihisa*; Koba, Yusuke*; Furuta, Takuya; Chang, W.*; Hashimoto, Shintaro; Yonai, Shunsuke*; Matsumoto, Shinnosuke*; Sato, Tatsuhiko
no journal, ,
There found to be a relationship between the dose-averaged linear energy transfer LETd and local tumor control in carbon-ion radiotherapy (CIRT). However, only physical dose and biological dose are registered in the past treatment records of CIRT in QST hospital and LETd can not be deduced directly. There is a method to estimate LETd based on RBE-LETd-fitted function but some problems such as non-singularity at the end point of carbon ions are known. On the other hand, we propose a method to reproduce the CIRT by reconstructing the beam transport geometry based on the treatment planning data and conduct Monte Carlo simulation. The LETd can be also computed directly. We therefore compared LETd obtained by Monte Carlo simulation with estimated LETd using the treatment planning data. We found that underestimation around the end point of carbon ions but the influence was local and thus the LETd estimates are valid for the purpose computing in organ scale.
