The response of rat thyroid, a highly differentiated tissue, to single and multiple doses of gamma or fast neutron irradiation

The RBE for 14·7 MeV neutron radiation in the thyroid, a highly differentiated tissue, was found to be 1·8 relative to 137Cs radiation at the 10 per cent survival level. Absolute dosimetry errors were 5 per cent for 14·7 MeV neutron irradiations, and 3 per cent for 137Cs irradiations. The index used was cell survival as estimated from goitrogen-induced cellular proliferation. Under fractionated conditions the RBE increased to 3·0. The relevance of these findings to clinical radiotherapy is discussed.