OICC Press Journal of Theoretical and Applied Physics 2251-7235 18 5 2024 10 30 Reducing secondary particle dose in proton therapy for gastric tumors: a material optimization study 1 11 10.57647/j.jtap.2024.1805.61 EN Nafise Asadi Jafari School of Physics, Damghan University, Damghan, Iran Mojtaba Tajik School of Physics, Damghan University, Damghan, Iran https://orcid.org/0000-0002-8714-5135 Journal Article 2024 10 30 Proton therapy treats tumors by delivering high doses (in the form of Bragg peaks) to the targetvolume while protecting healthy tissue from radiation. However, secondary particles producesome dose, particularly neutrons, with high relative biological effects. This study used MCNPXcode to investigate the impact of changing pre-collimator, snout, and diaphragm materials on thedose of secondary particles in proton therapy for gastric tumors. Results indicate that switchingfrom brass to nickel reduces the total average dose of protons and secondary particles in mostvital organs (excluding the tumor) by 44%. Additionally, the equivalent neutron dose to absorbeddose (H/D) in the brain decreased by 33%, and the average H/D in 14 vital organs dropped byapproximately 12%. These findings demonstrate that changing collimator materials from brass tonickel can significantly reduce the harmful effects of secondary particle doses, particularly neutrondoses, in gastric tumor treatment.