Gamma-background rejection method for a dual scintillator positron probe dedicated to radio-guided surgery

We developed a positron intraoperative probe with high sensitivity dedicated to real-time assessment of the resection margins of tumors and control of the surgical cavity. Its main limitation comes from the annihilation photon background generated by distal non-specific radiotracer uptakes. This study is a proof of concept for a dual-scintillator intraoperative probe with background subtraction capability. It associates a highly p-terphenyl β-sensitive scintillator and a highly γ-sensitive LYSO:Ce. Both scintillator are readout by a single pixelated photodetector based on SiPMs and the shape and intensity of the light distribution is used to identify in which scintillator the interactions occurred to allow further discrimination of the signals and subsequent quantification of this background can be utilized to have it subtracted from the raw images. We describe in this study the design of the probe and the analysis to achieve this identification with a good accuracy. An average efficiency of events identification of 97.90 ± 0.06% is reported on the whole field of view.