Fluence to Dose Equivalent Conversion Factors Calculated With EGS3 for Electrons from 100 keV to 20 GeV and Photons from 11 keV to 20 GeV

Abstract

The EGS3 Monte-Carlo electron-photon transport simulation package was used to calculate dose equivalent per unit fluence vs. depth curves for broad parallel beams of monoenergetic electrons, positrons and photons incident on a 30 cm thick slab of ICRU [International Commission on Radiological Units and Measurements] 4 element tissue. The electron kinetic energy range covered was 100 keV-20 GeV and that for photons was 11 keV-20 GeV. By making minor modifications. EGS3 was in reasonable agreement with other codes for electron energies down to 100 keV. Complete dose equivalent vs. depth curves as a function of electron and photon energy were presented to allow proper calculations of the maximum dose equivalent for a mixed photon and electron spectrum since there were substantial variations in the locations of the peak dose equivalent. Explicit calculations demonstrated that 1/r2 corrections gave an accurate means to convert results for broad parallel beams to those for point source geometries. The relative contributions of various physical processes to the peak dose equivalent were presented.