NEW ELECTRON BACKSCATTER CORRECTION FACTORS FOR ACCURATE SKIN DEPTH DOSE CALCULATION FROM SKIN CONTAMINATION BY HOT PARTICLES

Abstract

New backscatter correction factors have been calculated using the GEPTS Monte Carlo code system for the case of an isotropic electron point source located at the boundary of a semi-infinite water medium. The backscatter correction factor is defined as the ratio of the dose in a semi-infinite medium to the dose, at the same point, in an infinite medium. It is found that the backscatter correction factor variation with position inside the medium is significant. However, the backscatter correction factor variation with energy is quite small for electron energies less than 1 MeV. The backscatter correction factor data are tabulated for energies of 1, 2, 3, and 4 MeV as functions of radial distance and angular direction. The proposed backscatter correction factors can be used for skin depth-dose calculations from beta particles emitted by either point sources or planar sources. Arbitrary target volumes and beta particle spectra can be considered. The new backscatter correction factors provide an alternative to the current data for accurate skin depth-dose calculations from skin contamination by hot particles.