A comparison of the response of tumour and normal tissue in the mouse exposed to single doses of fast neutrons or electrons

Spontaneous mouse tumours were exposed to single doses of fast neutrons or fast electrons. Their response was compared with the damage caused to the overlying skin to obtain a measure of the therapeutic ratio for fast neutrons. At low doses the neutrons showed a large therapeutic gain, which reduced to unity (i.e. no gain) for large doses. This result is discussed in terms of the proportion of hypoxic cells and oxygen concentrations in the two tissues.