Room: Karl Dean Ballroom B1
Purpose: The advantage of proton therapy over conventional photon therapy is compromised by proton range uncertainty and dose monitoring is of critical importance to improve the precision of proton therapy. This abstract reports the design and performance evaluation of our prompt gamma image (PGI) system with 2D imaging capability for real-time proton therapy monitoring.
Methods: The PGI system consists of a tungsten multi-knife-edge slit collimator with a thickness of 60 mm, an array of high resolution scintillation detectors, ASIC-based readout electronics and a data acquisition module. The collimator has 7 vertical slits and 22 oblique slits placed at varying angles relative to the vertical slits to ensure 2D imaging capability. The detector module is composed of a 12Ã—12 BGO block (pixel size: 3.5mmÃ—3.5mmÃ—30mm) coupled to an 8Ã—8 SiPM array and totally 12Ã—10 detector modules are used to form the detector array. A customized ASIC is used to read out each detector block and extract energy and position information of gamma events. Spatial resolution, sensitivity and Bragg peak positioning accuracy of the system was investigated with Monte Carlo simulation using GATE. Positioning and energy performance of the detector module under MeV gamma energy is reported.
Results: A system sensitivity of 0.256% at FOV center is achieved. The spatial resolution is ~2.34 mm at proton incidence direction and ~2.86 mm at transverse direction. A Bragg peak positioning accuracy of ~2.3 mm is achieved. Experimental evaluation of the detector module indicates the feasibility and good positioning performance in the energy range (2~8MeV) of prompt gamma. An average energy resolution of 20.3%Â±2.7% at 1.275MeV is achieved.
Conclusion: We successfully developed a PGI system for real-time proton therapy monitoring. Monte Carlo simulation and initial experimental evaluation of the detector module demonstrate the feasibility of the system. Further system assembling and experimental performance evaluation are ongoing.
Funding Support, Disclosures, and Conflict of Interest: This work was partially supported by National Key R&D Program of China (No. 2016YFC0105405), National Natural Science Foundation of China (No. 81727807, No. 11275105, No. 11375096 and No. 11605008), China Postdoctoral Science Foundation (No. 2016M601046) and National "Twelve Five - Year" Plan for Science & Technology Support Program (No. 2015BAI42H00).