The Additivity of γ-Rays and Fission Neutrons in Producing Spleen Weight Reduction

Abstract

The percent spleen weight reduction, 5 days post-irradiation, is a function of log dose for both Co60 gamma-ray and fission neutrons for the dose ranges investigated. Neutrons are 4.42 times as effective per unit energy absorbed in splenic weight reduction from the 20% through the 80% range. The value at 50% weight reduction is 442 [plus or minus] 0.45. No departure from additivity could be demonstrated for combined doses of Co60 gamma-ray and fission neutrons in spleen weight reduction. This strengthens the hypothesis that these radiations are additive in producing hematological damage. This investigation, combined with others using splenic regression as a criterion, indicates that biological effectiveness per unit energy absorbed increases for radiations dissipating from 0.3 to 30 kev/u of path.