Calculated yields and slowing-down spectra for electrons in liquid water: implications for electron and photon RBE

Publisher Website
Google Scholar
Abstract
Detailed Monte Carlo calculations were carried out for slowing-down spectra and yields for a number of end-points for electrons in liquid water. These investigations were made to study differences in physical effects of different low-LET [linear energy transfer] radiations and implications for RBE [relative biological effectiveness]. Initial electron energies from 1 keV to 1 MeV were used, and all secondary electrons were followed in the computations until their energies fell below 10 eV. Though there are substantial differences in the slowing-down spectra at energies near and above the K-shell ionization potential of O2, the energy spectrum of electrons at lower energies is essentially independent of the initial energy of the primary electron. The number of events per unit energy deposited is also essentially independent of the primary electron energy. Based on these calculations, there appears to be little basis for ascribing differences in RBE for low-LET radiations to differences in physical effects produced by secondary electrons of low energy (.ltorsim. 1 keV).