The Effect of Fractionation on Four Day Survival of Mice after Whole-body Neutron Irradiation

Abstract

The proportion of animals surviving four days after whole body neutron irradiation is not altered by giving the radiation in two fractions separated by four to six hours. This result is compared with previously reported data after 250 kV X irradiation when it was found that a dose higher by 400–600 rads was necessary to produce the same killing effect if the radiation was given in two fractions rather than a single dose. This results in a larger RBE (250 kV/neutron) for the fractioned radiation than for single-dose irradiation and any increase in the number of fractions would increase the RBE further. These results may be relevant to the use of neutrons for therapy.