量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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The aim of this study is to investigate the radiobiological efficacy of heavy in beams by comparing RBE values of radioresistant human tumors and those of radioresistant human tumors and those of radiosensitive nomal tissues. Human brain tumors (two glioblastomas, an ependymoblastoma, and a primitive neuroectodermal tumor:ONET) were transplanted to nude mice subcutaneously, and the mice were irradiated with carbon ion beams (290MeV/u, 6cm SOBP) or 200kV X-rays, Tumors, brains, spleens, kidneys, livers, duodenums, and testes were excised 4, 6, 24 hours or 5 weeks after irradiation. They were stained with H.E., p53, Ki-67, GFAP or TUNEL, and microscopically examined to evaluate apoptosis and other histological changes. RBE values of carbon ion beams were more than 1.0, but the values varied according to the tumors, organs, and endpoints. RBE values evaluated by apoptosis were 3.0, 3.6, and 6.1 for the ependymoblastoma, the PNET, and the glioblastoma, resoectively. In contrast, RBE values for radiosensitive nomal tissues were 1.2-2.1. GFAP-positive cells in the ependymoblastoma increased following irradiation. Less histological changes were observed in normal brain tissues after carbon or X-ray irradiation. These results suggested that the heavy ion beams are more favorable for treating radioresistant tumors.
重粒子線のRBEと治療可能比の検討；放射線抵抗性腫瘍と正常組織の比較
