Speakers
Description
Silicon photomultipliers (SiPMs), also known as multi-pixel photon counters (MPPCs), represent an alternative solution that to a large extent combines the advantages of PMTs and APDs. They have high gain, low bias voltage, excellent timing properties and are insensitive to magnetic fields. SiPMs perhaps are the best readout choice for advanced positron emission tomography (PET) systems, such as PET/MRI instruments and time-of-flight (TOF) PET imaging. The most popular SiPM technology that is commercially provided by SensL, Hamamatsu and FBK etc., employs poly-silicon or metal quenching resistors at the device surface, and achieved energy resolution about 9% and coincidence time resolution around 120ps.
Unlike most commercial SiPMs, NDL SiPM uses the bulk resistors in the epitaxial layer as quenching resistor (EQR SiPM); it features small micro cells with high fill factor, fast response to even a single photon, and simple fabrication technology. In this conference, we report NDL EQR-SiPM as a candidate for PET detector readout. For detailed characterization of EQR SiPM based PET detectors, an architecture measuring 511keV gamma photons irradiated from a 18F-FDG source was set up, in which two EQR SiPMs are optically coupled to a pair of lutetium oxy-orthosilicate (LYSO) crystals, the outputted signals are fed to a digital oscilloscope to analyze energy information and perform coincidence processing. The EQR SiPM has active area of 3mm×3mm, comprising 90000 individual cells, a dark count rate of 6.3 MHz at 9 V overvoltage, a peak PDE of 34% for 420 nm photons and an intrinsic single photon timing resolution (SPTR) of 81 ps at the same voltage. The energy resolution (ER) of ~10.1 % and the coincidence timing resolution (CTR) of ~195 ps (FWHM) were obtained with the 2.84mm×2.84mm×6mm LYSO crystals. Saturation effects involved in most commercial SiPM with limited micro cells is negligible. Those results verify that EQR-SiPM is promising in applications of PET imaging.
