MPPC Arrays in PET Detectors With LSO and BGO Scintillators

Presently, a majority of studies concerning application of silicon photomultipliers (SiPMs) in positron emission tomography detectors are focused on scintillators containing lanthanum (LaBr₃) or lutetium (LSO, LYSO, or LFS). However, the modules with the well-known BGO in combination with SiPM light readout are also interesting, owing unique features of SiPMs. In this paper, the two types of detectors, based on BGO and LSO scintillators, are compared in terms of requirements for positron emission tomography scanners. The presented studies are performed with two Hamamatsu Multi Pixel Photon Counter (MPPC) arrays of 2 × 2 channels, with the total area of 6 × 6 mm² and micro-pixel size of 25 μm (S10985-025C) and 50 μm (S10985-050C). The measurements of a number of photoelectrons, energy resolution at 511 keV and ²²Na time resolution are reported for various sizes of the scintillators, including 2.75 × 2.75 × 20 mm³ pixel and single crystals covering the whole MPPC active area. The paper is more focused on optimization of the system with BGO as its performance in combination with SiPM light readout is less known. The aim of this work is to show advantages of a SiPM-based detector, especially in combination with BGO, in respect to the block detectors where classic photomultipliers are used.