Simulation Study of a 3-D Multislit Prompt Gamma Imaging System for Proton Therapy Monitoring

The Bragg peak phenomenon empowers proton therapy in targeted dose delivery in principle and also critically demands high accuracy of proton beam’s dispatch track in practice. To ensure the accuracy, prompt gamma imaging (PGI) systems were studied for monitoring the delivery of proton beams in real time. In this work, a dual-head PGI system was proposed and optimized with multislit collimators and BGO scintillators. The dual-head system was then assessed through a contrast recovery coefficient (CRC)-variance approach to identify a preferred setup. The performance of the PGI system was evaluated in terms of detection efficiency, spatial resolution, and positioning accuracy through a series of Monte Carlo simulations. Simulation results show that the detection efficiency of the system is 0.53% at the center of the FOV for 4.44 MeV prompt gamma, and the spatial resolution is better than 2 mm across the FOV. The positioning accuracy defined as the most distal edge position (MDEP) error is less than 2 mm along the beam incident direction at a relatively low number of detected events ( $5 \times 10^{4}$ ) in the dual-head system corresponding to a beam spot of $10 ^{8}$ incident protons. The system design is feasible for the real-time proton therapy monitoring.