@article{oai:repo.qst.go.jp:00047061,
 author = {Ando, Koichi and Koike, Sachiko and Ohmachi, Yasushi and Ando, Yutaka and Kobashi, Gen and 安藤 興一 and 小池 幸子 and 大町 康 and 安藤 裕 and 小橋 元},
 issue = {12},
 journal = {International Journal of Radiation Biology},
 month = {Dec},
 note = {Purpose : To determine the dose-dependent relative 
biological effectiveness (RBE) for tumor prevalence in mice
receiving single localized doses to their right leg of either 
carbon ions (15, 45 or 75 keV/ μ m) or 137Cs gamma rays.
Methods and materials : A total of 1647 female C3H mice 
were irradiated to their hind legs with a localized dose of 
either reference gamma rays or 15, 45 or 75 keV/ μ m 
carbon-ion beams. Irradiated mice were evaluated for 
tumors twice a month during their three-year life span, and 
the dimensions of any tumors found were measured with 
a caliper. The tumor induction frequency was calculated by
 Kaplan-Meier analysis.
Results : The incidence of tumors from 50 Gy of 45 
keV/ μ m carbon ions was marginally higher than those 
from 50 Gy of gamma rays. However, 60 Gy of 15 keV/ μ m 
carbon ions induced significantly fewer tumors than did 
gamma rays.  RBE values of 0.87± 0.12, 1.29 ± 0.08 or 
2.06 ± 0.39 for lifetime tumorigenesis were calculated for 
15, 45 or 75 keV/ μ m carbon-ion beams, respectively. 
Fibrosarcoma predominated, with no Linear Energy 
Transfer (LET)-dependent differences in the tumor 
histology. Experiments measuring the late effect of leg 
skin shrinkage suggested that the carcinogenic damage 
of 15 keV/ μ m carbon ions would be less than that of 
gamma rays.
Conclusions : We conclude that patients receiving radiation 
doses to their normal tissues would face less risk of 
secondary tumor induction by carbon ions of intermediate 
LET values compared to equivalent doses of photons.},
 pages = {1119--1124},
 title = {Tumor induction in mice after local irradiation with single doses of either carbon-ion beams or gamma rays},
 volume = {90},
 year = {2014}
}