Longer survival of the radiotherapy patients increases the likelihood of secondary cancers induced by the unavoidable irradiation of healthy tissue. Furthermore, secondary particles produced in the beam line components and within the patient's body by proton-induced nuclear reactions, mostly knocked-out neutrons but also photons, can deposit dose at large distances from the planned irradiation volume. Therefore, it is essential to study the complete deposition of energy as precisely as possible. Especially, neutrons are biologically very harmful and represent a major contributor to the risk of developing secondary malignancies following radiotherapy.
Within this Project we will simulate the distribution of the absorbed dose and LET in a tissue equivalent anthropomorphic phantom undergoing a typical radiotherapy treatment (e.g. prostate, lung or brain tumour) due to both, the primary and the secondary radiation. Further we will also register the neutron fluence and the energy spectra outside the planning target volume (PTV) in dependence of the energy of the initial proton beam. The neutron and the gamma-ray contributions to the total dose delivered to the PTV and outside the PTV will be investigated.
The final project results are likely to make a huge contribution to improvement of models in Monte Carlo codes, as the simulated data will be benchmarked to the measured data, and also to Treatment Planning Systems that don’t consider the target fragmentation.