In Vitro Cell Transformations Induced by 31 MeV Protons

Experimental data are presented on the frequencies of transformations in C3H10T1/2 cells exposed to 31 MeV protons (LET = 1.83 +/- 0.02 keV/mum in tissue) in a dose interval between 0.25 and 7.0 Gy. The transformation frequency per surviving cell curve showed a marked change in slope over the dose range used. At higher doses, above about 2 Gy, it steepened very sharply in comparison with the lower dose range. If fitted to a power of the dose, the power in the higher range was about five times that in the lower range.