The impact of modeling nuclear fragmentation on delivered dose and radiobiology in ion therapy

Abstract

Abstract.The importance of nuclear interactions for ion therapy arises from the influence of the particle spectrum on first, radiobiology and therefore also on treatment planning second, the accuracy of measuring dose and third, the delivered dose distribution. This study tries to determine the qualitative as well as quantitative influence of the modeling of inelastic nuclear interactions on ion therapy. Thereby, three key disciplines are investigated, namely, dose delivery, dose assessment, and radiobiology. In order to perform a quantitative analysis a relative comparison between six different descriptions of nuclear interactions is carried out for carbon ions. The particle transport is simulated with the Monte Carlo code SHIELD-HIT10A while dose planning and radiobiology are covered by the analytic treatment planning program for particles TRiP which determines the relative biological effectiveness (RBE) with the local effect model. The obtained results show that the physical dose distribution can in principle be significantly influenced by the modeling of fragmentation (about 10 % for a 20 % change in all inelastic nuclear cross sections for a target volume ranging from 15 cm to 25 cm). While the impact of nuclear fragmentation on stopping power ratios can be neglected the fluence correction factor may be influenced by the applied nuclear models. In contrast to the results for the physical dose, the variation of the RBE is only small (about 1 % for a 20 % change in all inelastic nuclear cross sections) suggesting a relatively weak dependence of radiobiology on the detailed composition of the particle energy spectrum of the mixed radiation field. Also, no significant change (about 0.2 mm) of the lateral penumbra of the RBE-weighted dose is observed.

The image quality of ion computed tomography at clinical imaging dose levels

“…For heavier ions, the models are not as accurate, 49,50 but has been shown to only have a minor impact on the dose average LET (Ref. 51) and thereby the Q W .…”

Report of a National Cancer Institute special panel: Characterization of the physical parameters of particle beams for biological research

“…Clinical facilities using passive scattering will significantly degrade the purity of the primary beam in front of the patient compared to scanning, where most of the fragmentation occurs in the patients’ body. The actual spectral composition of the beam may be of some importance in determining its biological effectiveness . The quality of the beam along a SOBP is generally characterized by its dose‐average.…”

“…The actual spectral composition of the beam may be of some importance in determining its biological effectiveness. 38 The quality of the beam along a SOBP is generally characterized by its dose-average.…”

Antiproton annihilation physics in the Monte Carlo particle transport code SHIELD-HIT12A

“…SHIELD-HIT12A is a Monte Carlo particle transport code, which was specifically developed for transport of ions in biological tissues [11][12][13] for research purposes [14,15], and is based on earlier versions as presented in [16,17]. The aim of this work is to benchmark SHIELD-HIT12A to simulate the antiproton depth dose curve in water correctly.…”