Performance characterization of a compact SPECT detector based on dSiPMs and monolithic LYSO

Silicon photomultipliers (SiPM) are a promising alternative light sensor for the classic photomultiplier tubes currently used as single photon emission computed tomography (SPECT) detectors due to their compact dimensions and smaller pixelization. Furthermore, these SiPMs are also known to be MR-hard which brings on new possibilities for simultaneous SPECT-MR imaging. In contrast to other research on SiPMs which is mainly focussed on PET applications, we will focus on SPECT imaging. The detector used in this work, consists of a dSiPM (DPC-3200-22-44, Philips Digital Photon Counting) optically coupled to a monolithic LYSO scintillator of 2mm thick. Using a collimated ⁵⁷Co source, a filter was developed to remove the dark count events from the spectrum and a comparison was made between the detection efficiency of the DPC-based detector and a PSPMT-based detector. Furthermore, the intrinsic spatial resolution was determined using both a resolution collimator and beam source measurements. The same beam source measurements were also used to calculate the energy resolution across the detector. Finally, the count rate performance of the DPC was investigated by measuring a decaying ^99mTc source in front of the detector. Measurements showed that, despite the presence of dark count events in the spectrum, the DPCs have approximately the same detection efficiency as our gold standard, the PSPMT. Furthermore, we demonstrate that the detector has an intrinsic spatial resolution of 0.486mm and an energy resolution of 22.3 %. This work demonstrates the usefulness of the DPCs as SPECT detectors.