Reducing secondary particle dose in proton therapy for gastric tumors: a material optimization study

Abstract

Proton therapy treats tumors by delivering high doses (in the form of Bragg peaks) to the target
volume while protecting healthy tissue from radiation. However, secondary particles produce
some dose, particularly neutrons, with high relative biological effects. This study used MCNPX
code to investigate the impact of changing pre-collimator, snout, and diaphragm materials on the
dose of secondary particles in proton therapy for gastric tumors. Results indicate that switching
from brass to nickel reduces the total average dose of protons and secondary particles in most
vital organs (excluding the tumor) by 44%. Additionally, the equivalent neutron dose to absorbed
dose (H/D) in the brain decreased by 33%, and the average H/D in 14 vital organs dropped by
approximately 12%. These findings demonstrate that changing collimator materials from brass to
nickel can significantly reduce the harmful effects of secondary particle doses, particularly neutron
doses, in gastric tumor treatment.