Mouse skin reactions to 40 MeV helium ion irradiation

The change of mouse skin was recorded periodically. Mice are periodically sacrificed to obtain irradiated skin specimens. The specimens are made into microscopic study preparations. 4He ion radiation dose applied to the skin ranges from 2,000 rads to 12,000 rads. 40MeV 4He ion beam is fairly stable. The study was repeated four times in total. When the beam position is in the center of scattering foil, Cobalt-60 gamma ray calibrateb one rad corresponded to 20-23 scattering 4He ion count detected by a solid state detector placed in the direction of 40 degree to the axis of down stream beam. One rad also corresponded to 0.52-0.55 nano-Ampere Farady cnp current placed in the center axis 80 centi-meter apart from the target foil. Monitoring with Farady cup current is more consistent, in which beam deviation from the center can not be detected. Hence the dose was monitored with the current with scattering helium count recorded. Depth dose was measured with TLD and 50% depth dose of plateau is approximately 0.08 g/cm. The skin was irradiated from 2,000 rads to 12,000 rads. In one week epilation starts. In two week complete epilation in all groups and in high dose groups (above 4,000 rads) at the same time erosions occur. In four weeks erosions heal. Higher dose group takes a little longer. In five weeks all erosins heal any way. Even the skin irradiated with 12,000 rads heals. Skin hypertrophy follows. The higher dose induces the more hypertrophy. Cell number in a hair follicle decreases with increased dose. Hair follicle itself decreases its number. (J.P.N.)