Evaluation of a Novel Multi-slit Collimated Detection System for Prompt Gamma-Ray Imaging During Proton Beam Therapy

Range uncertainty in proton therapy has a significant impact on the utilization and efficacy of the treatment modality. Several methods are under investigation to verify proton range by the detection of secondary emissions, with many studies focused on the use of prompt gamma-ray imaging (PGI) as a means to determine the Bragg peak location. This work introduces a new system and method of PGI using a multi-knife-edge slit collimator and detector. Initial measurements using 50 MeV protons demonstrated the ability of the system to provide 2-dimensional prompt gamma-ray (PG) distributions. A Bragg peak localization precision of 1 mm (2σ) was achieved with delivery of (1.7 ± 0.8) × 10
⁸
protons into a PMMA target from an 8 cm standoff distance, suggesting the ability of the system to detect relative shifts in proton range while delivering fewer protons than used in a typical treatment fraction. Additionally, the absolute position of the Bragg peak was identified to within 1.6 mm (2σ) with 5.6 × 10
¹⁰
protons delivered. The initial results are promising and warrant further investigation and system optimization for clinical implementation.