Electron slowing-down spectra in water for electron and photon sources calculated with the Geant4-DNA code.
Recently, a very low energy extension was added to the Monte Carlo simulation toolkit Geant4. It is intended for radiobiological modeling and is referred to as Geant4-DNA. Its performance, however, has not been systematically benchmarked in terms of transport characteristics. This study reports on the electron slowing-down spectra and mean energy per ion pair, the W-value, in water for monoenergetic electron and photon sources calculated with Geant4-DNA. These quantities depend on electron energy, but not on spatial or angular variables which makes them a good choice for testing the model of energy transfer processes. The spectra also have a scientific value for radiobiological modeling as they describe the energy distribution of electrons entering small volumes, such as the cell nucleus. Comparisons of Geant4-DNA results with previous studies showed overall good agreement. Some differences in slowing-down spectra between Geant4-DNA and previous studies were found at 100 eV and at approximately 500 eV that were attributed to approximations in models of vibrational excitations and atomic de-excitation after ionization by electron impact. We also found that the high-energy part of the Geant4-DNA spectrum for a 1 keV electron source was higher, and the asymptotic high-energy W-value was lower than previous studies reported.
Department of Medical Physics, Tom Baker Cancer Centre, 1331-29th Street NW, Calgary, AlbertaT2N 4N2, Canada. Oleg.Vassiliev@albertahealthservices.ca
Oleg N
ON
Vassiliev
D004583:Electrons; D009010:Monte Carlo Method; D017785:Photons; D013057:Spectrum Analysis / Q000379:methods*; D014867:Water
D014867:Water