Prism-PET super module with tapered crystals for high-resolution TOF-DOI brain PET

Brain-dedicated positron emission tomography (PET) scanner with time-of-flight (TOF) and depth-of-interaction (DOI) capabilities has transformative potential for advancing diagnosis and research in neurology. We recently introduced a novel singled-ended TOF-DOI Prism-PET detector module with tapered crystals to minimize light leak, enhance energy, DOI, and timing resolutions, and enable the first experimental report of optical photon TOF (oTOF)-based depth encoding at the detector module level. In this study, we developed the 2×2 Prism-PET super module by fabricating four tapered Prism-PET modules into a 2×2 array with interleaved multiplexing (iMux) scheme to alleviate the saturation effects for silicon photomultiplier (SiPMs) at edges and corners and mitigate a large number of readout channels. The super module consists of a 32 × 32 array of 1.5 X $1.5 \mathrm{X} 20 \mathrm{~mm}^{3}$ lutetium yttrium oxyorthosillicate (LYSO) crystals which were tapered down to 1.2 X $1.2 \mathrm{~mm}^{2}$ at the crystal-readout interface and coupled 4-to-1 to a 16 × 16 array of $3 \mathrm{X} 3 \mathrm{~mm}^{2}$ SiPM pixels on one end and to a prismatoid light guide array on the opposite end. All crystals in the 2×2 super module are clearly resolved from the flood histogram result. The full width at half maximum (FWHM) energy, energy-weighted DOI, oTOF-weighted DOI, and timing resolutions are $7.76+/-1.18 \%, 2.28+/-0.48 \mathrm{~mm}, 5.81+/-1.24 \mathrm{~mm}$ FWHM, and 311 ps respectively.