Chemical Protection against Absorber-Moderated Protons

Abstract

In a previous study (1), the dose-reduction factor (DRF) of p-aminopropiophenone (PAPP) in mice for 440-Mev protons was measured. The logical extension of this line of investigation with regard to the dependence of protection on the physical characteristics of proton radiations is clearly to study protection at other proton energies. To make such a study directly comparable with our preceding work, proton beams of energies other than 440 Mev and having equivalent purity, intensity, etc., would be required. A related but much more easily executed experiment is that in which radioprotection against a proton beam moderated in energy and in flux distribution by passage through an absorber is studied. This latter experiment has been carried out and is here reported. This method has certain advantages over those in which the radiations to be compared are produced by two different accelerators, since physical parameters of the radiation other than energy or particle type (duty cycle, repetition rate, beam geometry, etc.), if different for the two radiations, might conceivably also affect chemical protection and animal survival. Also, measurements of chemical protection in mice placed at successive positions along the path of a moderated 440-Mev proton beam might be considered a crude approximation to the measurement of chemical protection in successive regions of a large mammal placed in the beam path, each region of the large mammal being weighted in proportion to the relative