Low dose hypersensitivity and induced resistance of V79 cells after charged particle irradiation using 100 MeV/u carbon ions.

This work aimed to study the effects of low dose irradiation in order to detect possible deviations from the linear-quadratic dose dependence of survival after charged particle irradiation. Survival of V79 cells at low doses was studied using a semi-automated cell detection system similar to the DMIPS system. With such a technique, the precision of survival measurements is improved by avoiding the stochastic uncertainties of the conventional dilution assay. A significant hypersensitivity at low doses (0.1 Gy) has been detected for 100 MeV/u carbon ions, whereas for higher doses (up to 0.5 Gy) a transition to a plateau-like region is observed, which is consistent with the assumption of induced resistance. These results are apparently in contrast to earlier studies using high-LET radiation like, e.g. neutrons or negative pions, where the effect of induced resistance has been reported to be at least significantly reduced for single exposure experiments.