Nanoscale characterization of ion tracks: MC simulations versus analytical approach

Abstract

The goal of this work was to investigate the agreement of physical parameters related to the particle track structure on the nanometer scale, obtained by means of a detailed track structure simulation (PTra) as well as by a rapid analytical approach. Parameters describing the tracks of secondary electrons produced by 0.3 MeV/ u C6+-ions were of particular interest as those particles are densely ionizing. For this purpose, the target volume in form of a nanometric water cylinder was positioned at different radial distances from the ion trajectory and track structure parameters were determined as function of the radial distance. While the fluence of electrons through the target surface and the mean ionization cluster size obtained by both approaches were in good agreement, the probabilities of specific cluster sizes (one, two and three) turned out to be rather different in the two approaches. Abstract. The scope of this work was to investigate the agreement of physical parameters related to the particle track structure on the nanometer scale, obtained by means of a detailed track structure simulation (PTra) as well as by a rapid analytical approach. Parameters describing the tracks of secondary electrons produced by 0.3 MeV/u C 6+ -ions were of particular interest as those particles are densely ionizing. For this purpose, the target volume in form of a nanometric water cylinder was positioned at different radial distances from the ion trajectory and track structure parameters were determined as function of the radial distance. While the fluence of electrons through the target surface and the mean ionization cluster size obtained by both approaches were in good agreement, the probabilities of specific cluster sizes (one, two and three) turn out to be rather different in the two approaches.

A Mathematical Radiobiological Model (MRM) to Predict Complex DNA Damage and Cell Survival for Ionizing Particle Radiations of Varying Quality

“…The coefficient γ is defined as the ratio of the ionization cross sections of secondary electrons with a minimum energy capable to induce DNA damages to the total cross section (The total cross section is the sum of the excitation, ionization and elastic cross sections, respectively) [ 99 ]. In our paper, we examined two different values for the coefficient γ: the first one (γ = 0.0001), adopted by the authors [ 100 ], corresponds to secondary electrons with energy equal to or higher than the ionization potential of water molecules (10.79 eV) [ 101 ], while the second one (γ = 0.01) is an alternative value for the case that the energy of these electrons is equal or larger than 17.5 eV (this is the threshold energy for the induction of an SSB, according to [ 87 ]). In the latter case, the probability of an SSB induction is considered equal to 1.…”

Multiscale approach predictions for biological outcomes in ion-beam cancer therapy

“…A detailed analysis of fluence of secondary electrons on a cylinder enwraping a DNA twist was performed in ref. 41 where the results of the analytical approach were compared to those of Monte Carlo simulations. Values of the parameters entering Eqs (6 , 7 , 8) as well as the references for more detailed explanation of these numbers are summarized in Supplementary Table S1 (SI) .…”

Multiscale physics of ion-induced radiation damage

“…The calculation of N i were solved using the random walk approach (Bug et al, 2012). In that recent work, the random walk calculations were successfully compared with the Monte Carlo simulation of transport of secondary electrons.…”

“…These electrons as well as holes and radicals comprise a complicated track structure with a radial distribution of the dose, while the space between different tracks is largely undisturbed. A solution to this problem was suggested by the Katz approach in which the radial dose distribution is calculated and related to the inactivation of sub-cellnucleus targets (Butts and Katz, 1967;Katz et al, 1971;Cucinotta et al, 1999). The quality factor of radiation was introduced in order to relate the survival curve parameters to a given radiation, differentiating between track types, inactivation modes, the structural complexity of targets, etc.…”