Comparison of Geant4-DNA and RITRACKS/RITCARD: microdosimetry, nanodosimetry and DNA break predictions

TL;DR

This study compares Geant4-DNA and RITRACKS/RITCARD Monte Carlo codes to evaluate their predictions of DNA damage from HZE ions, focusing on microdosimetry, nanodosimetry, and DNA break outcomes, with improvements in Geant4 modeling.

Contribution

The paper provides a detailed comparison and validation of two Monte Carlo simulation tools for DNA damage prediction, including new developments in Geant4 with periodic boundary conditions.

Findings

Excellent agreement in microdosimetry and nanodosimetry spectra between the codes.

Discrepancies at low-energy depositions due to electron interaction model differences.

Validation of Geant4's new features against RITCARD DNA break predictions.

Abstract

This work aims at investigating the impact of DNA geometry, compaction and calculation chain on DNA break and chromosome aberration predictions for high charge and energy (HZE) ions, using the Monte Carlo codes Geant4-DNA, RITRACKS and RITCARD. To ensure consistency of ion transport of both codes, we first compared microdosimetry and nanodosimetry spectra for different ions of interest in hadrontherapy and space research. The Rudd model was used for the transport of ions in both models. Developments were made in Geant4 (v11.2) to include periodic boundary conditions (PBC) to account for electron equilibrium in small targets. Excellent agreements were found for both microdosimetric and nanodosimetric spectra for all ion types, with and without PBC. Some discrepancies remain for low-energy deposition events, likely due to differences in electron interaction models. The latest results obtained using the newly available Geant4 example ``dsbandrepair'' will be presented and compared to DNA break predictions obtained with RITCARD.