Feasibility of PET detector readout by high-density Silicon Photomultipliers with epitaxial quenching resistors

Silicon photomultipliers (SiPMs) have high gain, low bias voltage, excellent timing properties and are insensitive to magnetic fields, which have become the best readout choice for advanced positron emission tomography (PET) systems, such as PET/MRI instruments and time-of-flight (TOF) PET imaging. Novel Device Laboratory (NDL) has been developing an unique SiPM technology that uses the bulk resistors in the epitaxial layer as quenching resistors (EQR SiPM); it features small micro cells with high fill factor, fast response to even a single photon, and simple fabrication technology. This paper reports the results to verify that EQR SiPM is promising in the applications of advanced PET imaging. For the EQR SiPM with active area of 3 × 3 mm² and 90000 individual cells, the dark count rate of 6.3 MHz at room temperature, a peak PDE of 34% for 420 nm photons and an intrinsic single photon timing resolution (SPTR) of 81 ps at 9 V over-voltage were obtained. By employing a pair of EQR SiPMs 1-to-1 coupled with 2.84 × 2.84× 6 mm³ LYSO crystals, the energy resolution (ER) of ∼10.1% and the coincidence timing resolution (CTR) of ∼195 ps (FWHM) were demonstrated; by employing a pair of EQR SiPMs 1-to-1 coupled with 2.84 × 2.84× 10 mm³ LYSO crystals, the ER of ∼9.8% and the CTR of ∼226 ps (FWHM) were demonstrated.