Addition of neutron and gamma-ray fractions for intestinal damage.

The microcolony assay technique has been used to test the validty of summing equivalent doses per fraction of 14 MeV neutrons and gamma rays for mouse intestinal damage. For a 4-daily fraction schedule, in which the first one or two fractions are given as neutrons and the remainder as gamma rays, combined dose fractions calculated from a 4-fraction schedule of either radiation type alone produce the same level of damage within the limits of accuracy of the experiment.