Evaluation of an LYSO Based Multi-PMT Detector for both Positron and Single Photon Imaging Usage

In this research, characteristics of combination of H8500 PSPMTs to form a larger detection area is studied. A home-made linear divider circuit was built for the merged signals readout. Borosilicate glasses with several thicknesses (0-5 mm) were chosen for scintillation light sharing in crossover region. The effects of light guide and crossover region on separable crystal size were evaluated. According to the test results, an imaging gamma head with larger crystal block with 89 times 89 mm² covered area, composed of 2 mm LYSO pixels, was fabricated and tested. Measured performances showed that this imaging head worked fine in both 511 keV and lower energy gamma rays. Through count rate measurements, the influence of ¹⁷⁶Lu nature background for single photon imaging was also presented. These results showed that using light sharing and linear resistor chain techniques, combination of PMTs in X, Y directions to build a large area imaging detector is still able to keep the ability of positron and single photons detections. Separable crystal size was 2 mm with 2 mm glass applied for light sharing in current status.