[Skin injury after exposure to high-energy protons and helium ions]

The RBE of high-energy protons and helium ions was measured with respect to the proliferation rate, cell number of the epidermic basal layer, induction rate of aberrant mitoses, number and type of chromosome aberrations. The animals were examined on postradiation days 1 and 6 (i.e., when the proliferation rate of the first postradiation mitosis was at a maximum). The RBE coefficients of protons and helium ions were unity with respect to the reproductive cell death and cell number of the epidermic basal layer; 1.5 with respect to the formation of multiple cell aberrations; 1.2-1.5 with respect to exchange-type aberrations; and 1.6 with respect to the mitotic index variations. This gives evidence that in response to high-energy protons the nuclear apparatus of the cell undergoes profound lesions.