Development of a gamma-ray imager using a large area monolithic 4 × 4 MPPC array for a future PET scanner

Abstract

We report the development of a monolithic MPPC array, which consists of 3 × 3 mm² elements arranged as a 4 × 4 array manufactured by Hamamatsu applicable to next generation PET scanners. We show that the MPPC is suitable for time of flight PET applications by simple measurement using coincident back-to-back 511 keV gamma rays. We demonstrated that the MPPC has much better timing resolution of ~ 600 ps than the APD. We coupled the monolithic MPPC array with the Ce:LYSO and Pr:LuAG scintillator matrices as gamma-ray detectors. The energy resolutions were evaluated as ~ 14% with 662 keV gamma-rays and the Ce:LYSO achieved the best. We also used a resistor network readout circuit with some optimization. The averaged positional resolution is estimated as ~ 0.27 mm in both x and y directions, while the energy resolution of each pixel was 9.9% for 662 keV gamma rays. Finally we applied the GHz class fast sampling waveform acquisition system to improve performance, and demonstrated efficient noise reduction by the clear detection of 22 keV gamma rays.