ESTRO 2025 - Abstract Book

S3573

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

code. Pencil beam (PB) spots reaching the shallow, central, and most distal part of the tumors were selected for secondary FN simulations. 10 million primaries were simulated per PB spot.

Results: The prostate cancer case had the highest production of neutrons, with a neutron production rate per primary proton of 0.163, 0.133, and 0.106, for the energies 195, 175 and 158 MeV, respectively. The corresponding values were 0.058 (126 MeV), 0.038 (103 MeV), 0.022 (83 MeV) for the brain cancer simulation, and 0.037 (104 MeV), 0.023 (87 MeV), 0.015 (72 MeV) for the lung case. The distributions presented with quite different shapes reflecting different tissues and inhomogeneities along the beam paths (Figure A-C). Furthermore, the energy spectra of the generated neutrons were of similar shape for the different spots, although more distinct peaks in the spectra were observed for the highest spot energies (Figure D-F). The energies predominantly ranged from 1 to 100 MeV and the neutron energies generally increased with increasing initial energy.