Proton Range Verification Realized via a Multislit Prompt Gamma Imaging System

Proton therapy is one of the most advanced radiotherapy techniques. Despite its advantages in dose delivery, it has not yet achieved significant clinical benefits for patients due to uncertainties in proton range. Accurate, real-time monitoring of proton dose and range is crucial for ensuring the precision of proton therapy. In prior work, a dual-head prompt gamma imaging system was proposed and evaluated through Monte Carlo simulations, demonstrating high spatial resolution and sufficient detection efficiency for proton pencil beam imaging at clinical doses. This study focuses on the assembly, calibration, and testing of one of the detectors in this system. Spatial resolution and detection efficiency were evaluated using a 22Na point source, while range shift detection and accuracy were assessed with 60 and 100 MeV proton beams under low proton count conditions. The single-head system achieved a detection efficiency of 0.22% and a full-width at half-maximum (FWHM) spatial resolution of 2.8 mm at the center of the field of view (FOV). The system was able to detect a 1 mm range shift by identifying the most distal edge position (MDEP) of the prompt gamma profile. The detector demonstrated a range accuracy of less than 1 mm at typical count levels for a single spot in proton pencil beam scanning. The results suggest that this system performs well in terms of both detection efficiency and spatial resolution, and the system could achieve real-time range verification with high accuracy.