Evaluation of inelastic hadronic processes for 250 MeV proton interactions in tissue and iron using GEANT4

When high-energy protons interact in beam delivery systems and are stopped in patients, a fraction of beam will undergo nuclear interactions that release secondary particles, in particular, neutrons of different energies. The GEANT4 Monte Carlo Code was used to simulate the interaction of 250 MeV proton beam in tissue and iron to calculate the energy and angular distributions of generated protons, neutrons and photons, and thus provide H* (10), the ambient dose equivalent. A modular physics list by utilising electromagnetic interactions and hadronic interactions was constructed. Three different GEANT4 models that include the low-energy parameterisation, binary cascade and pre-compound model with Bertini cascade for proton inelastic interactions were compared. The findings suggest that the models play critical roles in terms of secondary particle generation. Further benchmarks are necessary to select the best model predicting a realistic scenario.