Abstract
It was reported that the dose-rate effects of X-rays or gamma-rays are, it is reported that the biological effectiveness decrease with decrease of the dose-rate (Joel S et al, 1973). Radiosensitivity of cell survival changes with the dose-rate among 0.2 Gy/hr - 60 Gy/hr (HP Leenhouts et al, 1990), for example. There are no reports concerning the change in radiosensitivity by heavy-ion exposure with different dose-rate. The dose-rate of heavy-ion is adjusted arbitrarily in the experiments in HIMAC. However, the influence of the dose-rate is not take account in the results. Thus, we studied the dose-rate effect on radiosensitivity of carbon-ion beams on cell survival.
Exponentially growing HSG cell line was irradiated and this was established from a human salivary gland tumor cultured in Eagle's MEM medium supplemented with 10% FBS and antibiotics. A 290 MeV/u carbon-ion beams accelerated at HIMAC having 18cm irradiation field and 70keV/μm were used with the dose-rate at 0.5, 6.0, 30, 36, 150, and 600 Gy/hr.
Dose-rate effect was not observed within the dose-rates tested and all the survival data were plotted on a survival curve. It is also found that there are no significant changes in survival parameters by the dose-rate. As in conclusion, there are no dose-rate effects on cell survival by carbon beam irradiation. Alternation of the dose-rate in experiments will not affect on experimental results. We will report some results from reference 60Co gamma-rays experiments.
