Lens Opacification in Mice Exposed to 14-MeV Neutrons

Abstract

The induction of lens opacification in mice exposed to 14-MeV neutrons was evaluated by counting the number of opacities observed in the posterior region of the lens using a slit-lamp microscope. The incidence of cataract formation in the anterior region of the lens was also observed. Serial observations were carried out from 3 up to 25 months after irradiation. Male hybrid mice (C54B1 X C3H), 75 days old at the time of the exposure, have been used. A linear progression of opacities was observed with age at a rate depending on the dose. By comparison with 250-kVp X rays the RBE was found to increase, with decreasing dose, from 9 to 21. The incidence of opacification in the anterior region of the lens gives an RBE value of 8. Split-dose irradiations were carried out with an interval of 24 hr between doses. There was very little difference in the number of opacities observed after single or fractionated neutron doses of approximately the same total amount. In contrast, fractionation of the X-ray dose reduced the effectiveness of the irradiation.