Impact of nuclear fragmentation on the stopping power ratio of¹²C ion beams

Objective: Nuclear fragmentation generates a diverse dosimetric environment in the path of¹²C ion beams. Concise parametrization of the beam's composition is paramount for determining key correction factors in clinical dosimetry. This study sets out to provide such a parametrization based on detailed Monte Carlo simulations of clinically relevant¹²C beams. Special attention was paid to the products of nuclear fragmentations and their importance in determining the stopping power ratios.Approach: Using the Monte Carlo simulation package GATE, the spectral fluence of all primary and secondary particles in water were computed at different depths for selected clinically relevant incident energies. Collision-stopping power data was taken from the ICRU90, SRIM and MSTAR database, as well as from previous publications.Main results: The choice of stopping power data was shown to have a bigger impact on the resulting stopping power ratio than the choice of physics lists for the simulations.Significance: A comprehensive analysis of the relationship between fragmentation and dosimetric data has been provided. This study compared different methods for determining spectral fluence-based stopping power ratios, which is essential for accurate ion beam dosimetry.