The Response of Pig Skin to Fractionated Treatments with Fast Neutrons and X rays

Abstract

The skin of pigs was used to study the effect of fractionated irradiation with fast neutrons of mean energy 6 MeV [million electron volts]. Six, 9 and 15 fractions were used over a period of 3 weeks, and 2 fractions divided by short intervals of time up to 24 hr. The effects of fractionated treatments with X-rays are also summarized. The RBE [relative biological effectiveness] of the neutron beam rises steadily from 2.3 for a single dose to 3.6 for 15 fractions. Observations up to 5 years after treatment failed to show any sign of increased late reactions after neutrons. There is less recovery during a fractionated course of treatment with fast neutrons than with X-rays, the relative amount of recovery, being 0.6. Very little recovery was observed during the 1st 7 hr. after treatment with neutrons. Reactions occurring after fractionated treatments withX-rays show that the number of fractions is more important than the time over which the treatment is extended, up to 28 days, but that prolongation is nevertheless a significant factor.