Comparison of nanodosimetric parameters of track structure calculated by the Monte Carlo codes Geant4-DNA and PTra

Abstract

The concept of nanodosimetry is based on the assumption that initial damage to cells is related to the number of ionisations (the ionisation cluster size) directly produced by single particles within, or in the close vicinity of, short segments of DNA. The ionisation cluster size distribution and other nanodosimetric quantities, however, are not directly measurable in biological targets and our present knowledge is mostly based on numerical simulations of particle tracks in water, calculating track structure parameters for nanometric target volumes. The assessment of nanodosimetric quantities derived from particle-track calculations using different Monte Carlo codes plays therefore an important role for a more accurate evaluation of the initial damage to cells and, as a consequence, of the biological effectiveness of ionising radiation. The aim of this work is to assess the differences in the calculated nanodosimetric quantities obtained with Geant4-DNA as compared to those of an ad-hoc particle-track Monte Carlo code developed at PTB. The comparison of the two codes was done for incident electrons of energy in the range between 50 eV and 10 keV, for protons of energy between 300 keV and 10 MeV, and for alpha particles of energy between 1 MeV and 10 MeV. Good agreement was found for nanodosimetric characteristics of track structure calculated in the high energy range of each particle type. For lower energies, significant differences were observed, most notably in the estimates of the biological effectiveness The largest relative differences obtained were over 50 %, however generally the order of magnitude was between 10 % and 20 %. P. Lazarakis et al.:Comparison of nanodosimetric parameters of track structure calculated by Geant4-DNA and PTB … 3 / 34

Geant4 interaction model comparison for dose deposition from gold nanoparticles under proton irradiation

“…Instead the ionisation cluster size distribution is scored in a volume representing a DNA segment of a few base pairs, and then is used to correlate radiation quality to DNA damage. This kind of calculation is more sensitive to the model selection (Lazarakis et al 2012) and further work is planned in order to elucidate the effect of the model selection in the presence of GNPs. RDDs calculated by Geant4 Monte Carlo simulations have been utilized in radiobiological models that predict cell survival.…”

Review of Geant4-DNA applications for micro and nanoscale simulations

“…Geant4-DNA simulations were performed in a cylindrical target volume (equivalent to 18 kbp of DNA) containing either the previously described detailed implementation of the double helix [71] or randomly oriented 10-bp long individual homogeneous cylinders as in [72], an approach commonly used in experimental nanodosimetry. Counting ionisations in scoring volumes and using their adapted DBSCAN algorithm in the detailed implementation of the double helix, they could compare the topology of ionisation clusters in both geometries using several nanodosimetric quantities.…”

“…Bug et al, [117] and Lazarakis et al [72] studied the effect of the magnetic field on the track structure of electrons, protons and alpha particles on the cluster size distribution in a DNA segment, modelled as a liquid water cylinder with nanometric sizes. The intensity of the magnetic field was varied from 0 to 14 T. The Geant4-DNA Package was adopted to model the physics interactions of particles in the set-up.…”

THE ENERGY DEPOSITION DISTRIBUTION AT THE MICRO AND NANO-SCALE FOR MOLECULAR TARGETED RADIOTHERAPY: COMPARISON BETWEEN 125I, 99MTc AND 64Cu

“…Both nucleus and cell were modeled as liquid water; b) Nano scale: absorbed doses were calculated in a volume corresponding to the DNA segment of 10 base pairs length and a nucleosome, both modeled as liquid water cylinders with nanometric dimensions [14]. Liquid water is the main constituent of the human body and represents a good approximation for the soft biological tissue [15].…”