title: Comparison of Monte Carlo calculated electron slowing-down spectra generated by 60Co gamma-rays, electrons, protons and light ions.
abstract: When analysing the factors affecting the relative biological effectiveness (RBE) of different radiation qualities, it is essential to consider particularly the low-energy slowing-down electrons (around 100 eV to 1 keV) since they have the potential of inflicting severe damage to the DNA. We present a modified and extended version of the Monte Carlo code PENELOPE that enables scoring of slowing-down spectra. mean local energy imparted spectra and average intra-track nearest-neighbour energy deposition distances of the secondary electrons generated by different radiation qualities, such as electrons, photons, protons and light ions in general. The resulting spectra show that the low-linear energy transfer (LET) beams, 60Co gamma-rays and electrons with initial energies of 0.1 MeV and higher, have as expected approximately the same electron slowing-down fluence per unit dose in the biologically important low-energy interval. Consistent with the general behaviour of the RBE of low-energy electrons, protons and light ions, the low-energy electron slowing-down fluence per unit dose is larger than for low-LET beams, and it increases with decreasing initial projectile energy.
authors.affiliation: Department of Medical Radiation Physics, Karolinska Institute and Stockholm University, Sweden. Nina.Tilly@onkologi.uu.se
authors.forename: N
authors.initials: N
authors.lastname: Tilly
authors.forename: J M
authors.initials: JM
authors.lastname: Fernández-Varea
authors.forename: E
authors.initials: E
authors.lastname: Grusell
authors.forename: A
authors.initials: A
authors.lastname: Brahme
mesh_terms: D003037:Cobalt Radioisotopes / Q000627:therapeutic use*; D003198:Computer Simulation; D004583:Electrons; D005720:Gamma Rays; D007477:Ions; D009010:Monte Carlo Method; D011522:Protons; D013997:Time Factors
chemical_list: D003037:Cobalt Radioisotopes; D007477:Ions; D011522:Protons