SU‐E‐T‐706: A GEANT4 Simulation of Light‐Ion Beams in Water

Abstract

Purpose: The purpose of this investigation has been to study the Bragg peaks of energetic light‐ions including H, Li, B, C, N, O, and Ne in water via a GEANT4 simulation to reveal potential benefits for radiation therapy. Methods: Electromagnetic processes for energy losses of hadrons and leptons are defined in GEANT4 as either “standard” (SP) or “low energy” (LEP). Our study used LEP for an extension of particle cutoff energies below that of SP. The hadronic interactions for proton and neutron were simulated using low energy elastic interactions and a binary cascade model. Other light‐ion hadronic interactions were simulated through the application of quasi‐molecular dynamics (QMD) model. A 27 liter water phantom consisting of 3000 packed rectangular detector discs (30 cm × 30 cm × 0.1 mm) was used in this simulation. The energy deposition in each disc was monitored to produce Bragg peaks. The simulations for each ion were carried out by 1 million incident particles with a pencil beam of 1 mm diameter. The energies of the ion beams were selected in order to create Bragg peak positions in three depths: 5, 15, and 25 cm. Results: The dose ratio of tail to peak was found to be 1.7 times higher for Ne compared to Li at 25 cm Bragg peak depth. It was found that Bragg peak widths at the 50% level decrease with increase of the atomic mass and this trend can be modeled with a power law. The entrance to peak dose ratio was found to be 1.35 times higher for Ne compared to protons at the 25 cm Bragg peak depth. At shallower depths, this dose increase with increasing atomic mass was not seen. Conclusions: This preliminary simulation demonstrates that GEANT4 is able to model multiple light‐ion beams for potential use in radiation therapy.