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 and Radiological Science and Technology.
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We carried out Biological effects of heavy ions have been extensively investigated using HIMAC synchrotron. One of major concerns about heavy particles is its carcinogenic potential. However, the data are still scanty. We previously showed that carbon-ion irradiation resulted in life span shortening and tumor induction in B6C3F1 mice1-3. It is known that a genetic background and an age at exposure are important factors. In the present study, we first focused on the influence of genetic background on the relative biological effectiveness (RBE) for cancer induction. Two mouse strains, C57BL/6 and C3H, were exposed weekly to whole-body carbon-ion or X-ray irradiation at 0.3-2.0 Gy for 4 consecutive weeks. Then, we investigated life span and tumor induction in these mice. C57BL/6 mice were highly susceptible to radiation-induced thymic lymphomas at the higher dose (1.2-1.6 Gy x 4), while C3H mice were resistant. The RBE of carbon-ions at the 50% incidence of thymic lymphomas in C57BL/6 mice was 1.1. RBE in C3H mice is under investigation. We also attempted to determine the influence of age at exposure for tumor induction. Male and female B6C3F1 mice at several age points were exposed to whole-body carbon-ion or g-ray irradiation at 0.2 and 2.0 Gy, and were observed under SFP condition.
重粒子線による発がんの被ばく時年齢依存性
