A Dual-head Prompt Gamma Imaging System for Online Monitoring in Proton Therapy

Proton therapy is one of the most advanced radiotherapy technologies. However, due to range uncertainty, real-time monitoring of proton dose deposition is of great importance in proton therapy.A dual-head prompt gamma imaging system has been proposed in previous work. The system design provides high spatial resolution and ensures enough detection efficiency for high signal-to-noise imaging during pencil beam scanning. In this work, the dual-head imaging system is assembled and calibrated. Detectability of range shift and range deviation accuracy are evaluated under 60 and 100 MeV proton beam. Detection efficiency (at the center of the FOV) and spatial resolution of the dual-head system are given by point source experiment.Range shift of 1 mm is able to be distinguished by the vertical detector by locating the most distal edge position (MDEP) of prompt gamma profile. Proton range deviation and range deviation accuracy of the vertical detector are both less than 1 mm at typical count level of a single spot in pencil beam scanning. Detection efficiency of the dual-head imaging system is 0.62% (FOV center) and ≤3 mm spatial resolution is achieved in the whole FOV.The dual-head prompt gamma imaging system shows excellent performance in detection efficiency and spatial resolution. Proton range shift detectability of the system is preliminarily verified. The system should be tested under clinical proton beam setup in future work.