The Effects of Total-Body Irradiation of Dogs with Simulated Fission Neutrons

Mongrel male dogs were exposed to neutrons obtained by bombarding a thick Be target with 12 Mev protons. The distribution of neutron and associated gamma-ray dose was measured throughout the volume of a tissue equivalent phantom constructed to simulate an average dog. The median lethal midline tissue dose is 239 rads, of which 165 rads are from neutrons and 74 rads are from gamma rays. The potency ratio, compared with 250 kvp x rays is approximately 0.9, in good agreement with the value of 0.95 found by other workers with a higher energy neutron beam. Thc significance of this potency ratio in terms of the gastrointestinal and bone marrow injuring potential of neutrons is discussed and the idea is presented that death after neutron irradiation of dogs is almost purely the result of bone marrow injury while death in rodents is the result largely of injury to the gastrointestinal tract. (auth)