Abstract：
PURPOSE: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. METHODS: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. RESULTS: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. CONCLUSIONS: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.
journal_name
Med Physjournal_title
Medical physicsauthors
Lau A,Chen Y,Ahmad Sdoi
10.1118/1.4735388subject
Has Abstractpub_date
2012-06-01 00:00:00pages
3773issue
6Part14eissn
0094-2405issn
2473-4209journal_volume
39pub_type
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