Two-Dimensional Prompt Gamma Measurement Simulation for In Vivo Dose Verification in Proton Therapy: A Monte Carlo Study

Abstract

In proton therapy, accurate verification of in vivo dose distribution is necessary to ensure not only the safety of the patient but also the success of the treatment itself. It has been shown, both by Monte Carlo simulations and by limited experiments, that the proton beam range in a patient can be accurately determined by measuring the distribution of the prompt gammas generated from proton-induced nuclear interactions. In the present study, a two-dimensional (2-D) prompt gamma detection system incorporating a 51 (longitudinal) × 21 (lateral) detector array was designed and tested by Monte Carlo simulations using the MCNPX code. Additionally, the detection probability of the prompt gammas per primary proton was calculated for different proton energies. Despite the increase of the beam dispersion effect and background gammas with the increase of the proton energy, our simulation results clearly showed that it is possible to measure the 2-D distribution of prompt gammas up to 150 MeV using the 2-D prompt gamma detection system.