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Journal Articles

Development of next-generation superconducting cyclotron

Ishiyama, Atsushi*; Ueda, Hiroshi*; Fukuda, Mitsuhiro*; Hatanaka, Kichiji*; Miyahara, Nobuyuki*; Yokota, Wataru; Kashima, Naoji*; Nagaya, Shigeo*

Denki Gakkai Kenkyukai Shiryo, Chodendo Oyo Denryoku Kiki Kenkyukai (ASC-10-33), p.83 - 88, 2010/06

Therapy of tumor using radiation, especially heavy particle, is one of the effective treatment for an aged person and a malignant solid tumor. In order to spread the radiation therapy, downsizing of accelerator is necessary for reduction of its vast costs of construction and running. The quality of high temperature superconductors is improving rapidly in recent years, which may lead to realization of the downsizing. This presentation describes a conceptual design of the superconducting cyclotron and its advantage comparing to other type of accelerators.

Journal Articles

Calculation of dose contributions of electron and charged heavy particles inside phantoms irradiated by monoenergetic neutron

Satoh, Daiki; Takahashi, Fumiaki; Endo, Akira; Omachi, Yasushi*; Miyahara, Nobuyuki*

Journal of Radiation Research, 49(5), p.503 - 508, 2008/09

 Times Cited Count:7 Percentile:27.27(Biology)

The radiation-transport code PHITS with an event generator mode has been applied to analyze energy depositions of electron and charged heavy particles in two spherical phantoms and a voxel-based mouse phantom upon neutron irradiation. The calculations using the spherical phantoms quantitatively clarified the type and energy of charged particles which are released through interactions of neutrons with the phantom elements and contribute to the radiation dose. The relative contribution of electrons increased with increase in the size of the phantom and with decrease in the energy of the incident neutrons. Calculation with the voxel-based mouse phantom given 2.0-MeV neutron irradiation revealed that the doses to different locations inside the body are uniform, and that the energy is mainly deposited by recoil protons. The present study has demonstrated that analysis using PHITS can yield dose distributions that are accurate enough for RBE evaluation.

Journal Articles

Microdosimetric study for secondary neutrons in phantom produced by a 290 MeV/nucleon carbon beam

Endo, Satoru*; Tanaka, Kenichi*; Takada, Masashi*; Onizuka, Yoshihiko*; Miyahara, Nobuyuki*; Sato, Tatsuhiko; Ishikawa, Masayoshi*; Maeda, Naoko*; Hayabuchi, Naofumi*; Shizuma, Kiyoshi*; et al.

Medical Physics, 34(9), p.3571 - 3578, 2007/09

 Times Cited Count:7 Percentile:26.01(Radiology, Nuclear Medicine & Medical Imaging)

Absorbed doses from main charged particle beams and charged-particle fragments have been measured with high accuracy for particle therapy but there are few reports for doses from neutron components produced as fragments. This study describes measurements on neutron dose produced by carbon beam, microdosimetric distributions of secondary neutrons produced by 290 MeV/nucleon carbon beams have been measured by using a tissue equivalent proportional counter (TEPC) at the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). The ratios of neutrons to charged particle fragments dominated to be 11 to 89 % in the absorbed doses at the side and below the faces of the acrylic phantom (300 mm height $$times$$ 300 mm width $$times$$ 253 mm thickness).

Journal Articles

Simulation analysis of radiation fields inside phantoms for neutron irradiation

Satoh, Daiki; Takahashi, Fumiaki; Endo, Akira; Omachi, Yasushi*; Miyahara, Nobuyuki*

JAEA-Conf 2007-002, p.59 - 65, 2007/02

The present study intends to analyze internal radiation field of a typical mouse with voxel phantom and radiation transport code. A mouse was imaged by using the dedicated small-animal CT scanner, in which slice pitch was set at 0.1 mm. Each image with the resolution of 0.02 mm was segmented to construct a voxel phantom by using computer tools, which have been applied to process human-head images for 3-dimensional dosimetry in BNCT treatment at the Japan Atomic Energy Agency. Input files for particle and heavy ion transport code system were prepared from the constructed 3-dimensional voxel-based image data. Absorbed dose distributions and LET spectra in the mouse body were calculated by PHITS on the segmented images.

Oral presentation

Simulation of internal radiation field using voxel-based model of mouse

Satoh, Daiki; Takahashi, Fumiaki; Endo, Akira; Yamaguchi, Yasuhiro; Omachi, Yasushi*; Miyahara, Nobuyuki*

no journal, , 

The present study intends to analyze internal radiation field of a typical mouse with voxel-based model and radiation transport code. A mouse was imaged by using the dedicated small-animal CT scanner, in which slice pitch was set at 0.1 mm. Each image with the resolution of 0.02 mm was segmented to construct a voxel-based model by using computer tools, which have been applied to process human-head images for 3-dimensional dosimetry in BNCT treatment at the Japan Atomic Energy Agency. Input files for particle and heavy ion transport code system (PHITS) were prepared from the constructed 3-dimensional voxel-based image data. Absorbed dose distributions and LET spectra in the mouse body were calculated by PHITS on the segmented images.

Oral presentation

PHITS simulation on internal radiation fields at neutron irradiation

Satoh, Daiki; Takahashi, Fumiaki; Endo, Akira; Omachi, Yasushi*; Miyahara, Nobuyuki*

no journal, , 

Internal radiation field of a typical mouse was analyzed by PHITS using a voxel-based model. A mouse was imaged by using the dedicated small-animal CT scanner, in which slice pitch was set at 0.1 mm. Each image with the resolution of 0.02 mm was segmented to construct a voxel-based model by using a computer tool JCDS, which have been applied to process human-head images for 3-dimensional dosimetry in BNCT treatment at the Japan Atomic Energy Agency. Input file for PHITS was prepared from the constructed 3-dimensional voxel-based image data. Distribution of deposition energy inside a mouse was calculated on the segmented images.

Oral presentation

Simulation analysis for organ doses of mouse and human upon neutron exposure by use of voxel phantoms

Satoh, Daiki; Sato, Kaoru; Takahashi, Fumiaki; Endo, Akira; Miyahara, Nobuyuki*; Tsuji, Atsushi*; Omachi, Yasushi*

no journal, , 

The present study intends to calculate the organ doses and analyze the characteristics of the radiation field inside the bodies of a mouse and human. The voxel phantom of mouse had already been developed for an 8-week-old C$$_{3}$$H/HeNs mouse in the previous work. We upgraded this phantom to improve the resolution (voxel size: 0.1$$times$$0.1$$times$$0.1 mm$${^3}$$), and add the nine solid organs. The JM phantom is the voxel phantom of a Japanese adult male developed for the analysis of internal exposure from photons and electrons. We have converted the JM phantom to use in the dose calculation on external neutron exposure, and verified it through the calculation of the absorbed dose per unit neutron fluence at each organ for monoenergetic neutrons. The calculation results showed a good agreement with the reference values reported by ICRP. From the comparison between the organ doses of the mouse and human, it was found that the relativistic dose contribution of electron in the human body is greater than that in the mouse body. This is because the neutrons are moderated inside a large receptor such as the human body, and causes the thermal neutron capture reaction that generates $$gamma$$ ray and consequently electron.

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