The influence of nuclear models and Monte Carlo radiation transport codes on stray neutron dose estimations in proton therapy

This study investigates the influence of several Monte Carlo radiation transport codes and nuclear models on simulation secondary neutron spectra its impact calculating measuring doses in proton therapy. Three different multi-purpose (FLUKA, MCNPX, Geant4) were used with available to calculate energy at various points inside a water tank phantom PMMA walls using 10 cm x rectangular, mono-energetic beam (110, 150, 180, 210 MeV). Using Kerma approximation calculated applying fluence-to-dose equivalent conversion coefficients water. Moreover, varying for electrochemically etched CR39 detector calibration was analyzed models. In distal positions beyond Bragg peak, results show largest variations between codes, up 53% high fluence 16 from peak 110 MeV beam. lateral positions, variation is smaller total within 20%. Variation MCNPX only visible energies 180 modeling which reached 23% 11 axis. Impact dose limited (<8%) while it pronounced (45% beam). factors average 10% 5 % models.This demonstrated large by proved be less prominent