Program Information
A Feasibility Study of Using a Cherenkov Detector Material with the Prompt Gamma Range Verification Technique in Proton Therapy
A Lau*, S Ahmad , Y Chen , University of Oklahoma Health Sciences Center, Oklahoma City, OK
Presentations
MO-FG-303-5 (Monday, July 13, 2015) 4:30 PM - 6:00 PM Room: 303
Purpose:To simulate the feasibility of a Cherenkov glass material for the determination of the penetration depth of therapeutic proton beams in water.
Methods:Proton pencil beams of various energies incident onto a water phantom with dimensions of 5 x 5 x 30 cm³ were used for simulation with the Geant4 toolkit. The model used standard electromagnetic packages, packages based on binary-cascade nuclear model, several decay modules (G4Decay, G4DecayPhysics, and G4RadioactiveDecayPhysics), and optical photon components (G4OpticalPhysics). A Cherenkov glass material was modeled as the detector medium (7.2 g of In2O3 + 90 g cladding, density of 2.82 g/cm³, Zeff = 33.7, index of refraction n(600 nm) = 1.56, and energy threshold of production Eth = 156 keV ). The emitted secondary particles are analyzed characterizing their timing, energy, and angular distributions. A feasibility analysis was conducted for a simplistic detector system using this material to locate the position of the Bragg Peak.
Results:The escaping neutrons have energies ranging from thermal to the incident proton energy and the escaping photons have energies >10 MeV. Photon peaks between 4 and 6 MeV were attributed to originate from direct proton interactions with ¹²C (~ 4.4 MeV) and ¹⁶O (~ 6 MeV), respectively. The escaping photons are emitted isotropically, while low (≤10 MeV) and high (>10 MeV) neutrons are isotropic and forward-directional, respectively. The emissions of photons are categorized into prompt (~ns) and delayed (~min) where the prompt photons include the 4.4 and 6 MeV. The Cherenkov material had on average <2% of neutron interactions while LYSO and BGO scintillators had a minimum of ~50%. Our simplistic detector system was capable of discerning Bragg Peak locations using a timing discrimination of ~50 ns.
Conclusion:We investigate the viability of using the Cherenkov material for MeV photon detection medium for the prompt gamma technique.
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