SU-E-T-302: A Simulation Study with Geant4 Investigating the Secondary Prompt Gamma Emissions from Incident 40 MeV Protons Onto Various Materials.

Abstract

This study aims to investigate the prompt secondary gamma spectrum and thedepth-dose distributions of incident 40 MeV protons onto various phantom materials.The goal is to find a relationship between the secondary prompt gamma emissions andthe range of the incident particles. An application was constructed using the Geant4 Monte CarloToolkit utilizing various physics packages. Several phantom materials were irradiatedwith a pencil beam of 40 MeV protons. These materials include PMMA (C5H8O2,density 1.18 g/cm3 ) and the built-in Geant4 materials bone, soft-tissue, and water. Foreach simulation, the energy deposited from the incident proton was recorded every 1 mmincrement of depth in the phantom. The resulting prompt secondary gamma emissionswere recorded from 0 to 10 MeV in energy bins of 10 keV. The secondary prompt gamma spectrum has various peaks. The peaks locatedabout 4.4 and 6 MeV correspond to the carbon and oxygen de-excitation photons,respectively. Our simulations show greater production of the higher-energy gammaparticles closer to the Bragg-Peak. When we plot the oxygen peak against the normalizedBragg-Peak we found that in all materials the difference between Bragg-Peak and theoxygen de-excitation photon peak to be about 2 mm. The oxygen peak could be used inthe clinic for range verification of the incident proton beam. Our Geant4 Monte Carlo application was used to investigate the secondaryprompt gamma emissions from incident 40 MeV protons. A relationship was betweenthe 6 MeV peak and the incident proton Bragg Peak. We believe that prominent peaksaround 4 and 6 MeV can be used to locate the range of the incident beam provided adetector system is built that can count these high-energy gamma particles.