Impact of nuclear fragmentation on the stopping power ratio of ¹²C ion beams

<i>Objective</i>: 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.<i>Approach</i>: 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.<i>Main results</i>: 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.<i>Significance</i>: 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.