Detector design for a high-resolution and high-sensitivity breast-dedicated multiplexed PET (mPET) scanner

Objective. We are developing a high-resolution, high-sensitivity breast-dedicated PET scanner that can image the distribution of multiple tracers simultaneously, referred to as multiplexed PET (mPET). This requires the detector to have high intrinsic spatial resolution and detection efficiency, as well as resolve photon depth-of-interaction (DOI).Approach. The detector array design comprises a novel trapezoidal shape configuration with scintillation crystal rod elements of different lengths to enable adequate intrinsic detection efficiency for prompt gamma ray photons (>511 keV) in addition to 511 keV photons, which is also practical to fabricate and assemble. The LYSO element lengths range from 5 mm to 35 mm, with a 1.28 mm pitch, read out by a multi-pixel photon counter (MPPC) array with a 3 mm pixel size. A light-sharing approach, combined with unpolished crystal surfaces and top-side light guides, enables DOI encoding. A prototype detector module was experimentally evaluated for flood image/crystal element separation, energy, DOI, and detector timing resolution. Measurements were performed under both side-irradiation and top-irradiation setups to assess the detector's performance across different interaction positions.Main results. The prototype detector flood image successfully resolved crystal elements even for 35 mm length crystals. DOI resolutions in full width at half maximum measured 4-6 mm for crystal lengths ranging from 10 mm to 30 mm and 7-8 mm for the 35 mm crystal length. Energy resolutions varied from 13% to 28%, with degradation observed at positions farther from the MPPC array plane. Detector time resolution values ranged from 330 ps to 660 ps.Significance.This work introduces a novel, single-ended readout, DOI-capable detector design that optimizes sensitivity while maintaining high spatial resolution for a breast-dedicatedmPET system, utilizing a unique trapezoidal crystal array and light-sharing DOI encoding designs. Additionally, this design offers a scalable approach that can be adapted to other high-performance PET systems.