A novel, SiPM-array-based, monolithic scintillator detector for PET

Silicon photomultipliers (SiPMs) are of great interest to positron emission tomography (PET), as they enable new detector geometries, for e.g., depth-of-interaction (DOI) determination, are MR compatible, and offer faster response and higher gain than other solid-state photosensors such as avalanche photodiodes. Here we present a novel detector design with DOI correction, in which a position-sensitive SiPM array is used to read out a monolithic scintillator. Initial characterization of a prototype detector consisting of a 4 × 4 SiPM array coupled to either the front or back surface of a 13.2 mm × 13.2 mm × 10 mm LYSO:Ce3+ crystal shows that front-side readout results in significantly better performance than conventional back-side readout. Spatial resolutions <1.6 mm full-width-at-half-maximum (FWHM) were measured at the detector centre in response to an ~0.54 mm FWHM diameter test beam. Hardly any resolution losses were observed at angles of incidence up to 45°, demonstrating excellent DOI correction. About 14% FWHM energy resolution was obtained. The timing resolution, measured in coincidence with a BaF2 detector, equals 960 ps FWHM.RRR/Radiation, Radionuclides and ReactorsApplied Science

LaBr3:Ce and SiPMs for time-of-flight PET: Achieving 100 ps coincidence resolving time

The use of time-of-flight (TOF) information in positron emission tomography (PET) enables significant improvement in image noise properties and, therefore, lesion detection. Silicon photomultipliers (SiPMs) are solid-state photosensors that have several advantages over photomultiplier tubes (PMTs). SiPMs are small, essentially transparent to 511 keV gamma rays and insensitive to magnetic fields. This enables novel detector designs aimed at e.g. compactness, high resolution, depth-of-interaction (DOI) correction and MRI compatibility. The goal of the present work is to study the timing performance of SiPMs in combination with LaBr3:Ce(5%), a relatively new scintillator with promising characteristics for TOF-PET. Measurements were performed with two, bare, 3 mm × 3 mm × 5 mm LaBr3:Ce(5%) crystals, each coupled to a 3 mm × 3 mm SiPM. Using a 22Na point source placed at various positions in between the two detectors, a coincidence resolving time (CRT) of ~100 ps FWHM for 511 keV annihilation photon pairs was achieved, corresponding to a TOF positioning resolution of ~15 mm FWHM. At the same time, pulse height spectra with well-resolved full-energy peaks were obtained. To our knowledge this is the best CRT reported for SiPM-based scintillation detectors to date. It is concluded that SiPM-based scintillation detectors can provide timing resolutions at least as good as detectors based on PMTs.RRR/Radiation, Radionuclides and ReactorsApplied Science