Investigation of optimized prompt gamma detection strategy for real-time Bragg Peak tracking in proton radiation therapy

Prompt gamma (PG) ray signal from proton radiation has been proposed for in vivo beam range verification to provide unique real-time tracking of the Bragg Peak (BP) during proton therapy (PT) delivery. In this study, we investigate possible strategies to optimize PG detection for BP tracking in proton radiation therapy. Extensive Geant4 Monte Carlo (MC) simulations have been used to study the energy spectral, spatial and timing characteristics of PG emission signal from 200 MeV proton pencil beam irradiations with water and PMMA phantoms. These include their relationship with the position of the BP and the background of the neutron field originated by the proton beams. Then the optimal energy window, angular window and timing window for PG imaging detection can be determined. Our results show that there could exist an optimal energy window for PG detection around 4.44 MeV. PG emissions show a backward angular preference while neutron emissions have a forward angular preference. Furthermore, employing a timing window could further improve the PG signal detection from strong background interferences of neutrons. Both energy and time resolved PG detection is a promising solution. These results indicate that there could exist an optimized strategy for PG signal detection. Utilizing appropriate energy window, angular window and timing window, PG image formation could be significantly improved for BP tracking.