SiPM-array based PET detectors with depth-of-interaction correction

We developed a novel high-resolution detector with intrinsic depth-of-interaction (DOI) correction for PET, based on a position-sensitive silicon photomultiplier (SiPM) array coupled to a monolithic scintillation crystal. The spatial distribution of the scintillation light measured by the SiPM array is used to estimate the entry point of the annihilation photon on the crystal front surface. This approach offers the benefit of intrinsic DOI correction. SiPM arrays furthermore enable integration of these detectors in a MRI device while offering faster response and much higher gain than APDs. Initial characterization of a detector prototype consisting of a 13.2 mm × 13.2 mm × 10 mm monolithic LYSO:Ce³⁺ scintillator and a 4 × 4 SiPM array shows that front surface readout (FSR) of the crystal results in significantly better performance than conventional back-surface readout (BSR). PSFs of ≪ 1.6 mm FWHM were measured at the centre of the detector (uncorrected for the ∼0.54 mm FWHM test beam diameter). Hardly any loss of spatial resolution was observed for angles of incidence of up to 45°. Energy resolutions of ∼12% were obtained. The timing resolution, measured in coincidence with a BaF2 detector, equaled 960 ps FWHM.