Comparison of Monte Carlo calculated electron slowing-down spectra generated by 60Co γ-rays, electrons, protons and light ions

• Published in: Physics in medicine & biology 2002-04, Vol.47 (8), p.1303-1319
• Main Authors: Tilly, N, Fernández-Varea, J M, Grusell, E, Brahme, A
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cobalt Radioisotopes - therapeutic use; Computer Simulation; Electrons; Gamma Rays; Investigative techniques, diagnostic techniques (general aspects); Ions; Medical sciences; MEDICIN; Medicin och hälsovetenskap; MEDICINE; Miscellaneous. Technology; Monte Carlo Method; Protons; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Time Factors
• ISSN: 0031-9155; 1361-6560; 1361-6560
• DOI: 10.1088/0031-9155/47/8/306

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.