Dose-Dependence of Fast Neutron RBE for Lens Opacification in Mice

Opacification of the optic lens in mice has been evaluated after exposure to the following radiations and doses: 250 kVp x-rays, 4.5-1,000 rads; 14 MeV neutrons, 0.5-60 rads; 1.8 MeV ncutrons, 1-36 rads; and 0.43 MeV neutrons, 0.02-104 rads.Highly refined techniques of serial in vivo lens examination and scoring of minute defects (opacities) were employed for tliis very radiosensitive System.Data analysis was based on the relative accumulation of opacities in irradiated compared to untreated lenses.(Both revealed the same degenerative process.)A nonparametric analysis of the Observation discloses tliat the RBE is inverscly proportional to the Square root of the neutron dose and that it can reach values in excess of 100.The findings are in accord with the theory of dual radiation action.