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Description
PET imaging continues to experience limitations, in part, due to lack of 3D detector spatial resolution and time of flight (TOF) detector temporal resolution. In this work, LYSO scintillator rods were characterized with silicon photomultiplier (SiPM) readout to evaluate their use in a proposed 3D PET detector module with properties suitable for TOF measurements. Three different polished scintillator rod coatings (no wrapping/ bare, wrapped in a 3M enhanced specular reflector (ESR), wrapped in Teflon tape) were investigated in an attempt to optimize energy resolution and transport of optical photons in 3 x 3 x 15 mm3 LYSO crystal rods. Signal versus irradiation position, using a 22Na positron source and single-sided and dual-sided silicon photomultiplier (SiPM) readout was quantified for 3 x 3 x 15 mm3 LYSO crystal rods for each of the three crystal coatings. The crystal rods were irradiated with a 22Na source and data was acquired with a single-sided readout as well as dual-sided readout geometry for each crystal coating. The best energy resolution was found to be (16.6 ± 3.4)% for the bare crystal, (20.7 ± 4.6)% for the ESR wrapped crystal and (26.7 ± 4.7)% for the crystal wrapped in Teflon tape. A coincidence resolving time (CRT) of (125 ± 53) nS FWHM was measured with two SiPMs coupled to 3 x 3 x 3 mm3 LYSO crystals. Signals from the SiPMs were routed through analog nuclear instrumentation (NIM) bin electronics. The 3 x 3 x 15 mm3 LYSO crystal rods with ESR coatings on three sides were then assembled in a two layer array with five parallel rods per layer. The first layer of scintillator rods is placed at 90° with respect to the second layer. This “crossed rod” scintillator geometry aims to decouple spatial resolution and temporal resolution from sensitivity, so that each parameter can be optimized independently.
