“…The miniaturization of a PET system is seriously limited as a result of the large volume and high working voltage of PSPMT. A silicon photomultiplier (SiPM), also referred to as a multi pixel photon counter (MPPC), according to the operation principle, as a new type of semiconductor device, is gradually replacing the PSPMT in a new generation of photodetectors in PET systems [ 13 , 14 , 15 , 16 , 17 ] based on the advantages of high quantum efficiency, high gain, fast time response, low operating voltage, compact structure, and immunity to magnetic fields [ 18 , 19 , 20 ].…”