Comparison of Timing Measurement Methods of Dual-Ended Readout Scintillator Array PET Detectors

The main focus of this work is to compare different timing measurement methods of individual silicon photomultiplier (SiPM) arrays and dual-ended readout PET detectors. Two lutetium yttrium oxyorthosilicate (LYSO) crystal arrays with $3.10\times 3.10\times 20$ - ${\mathrm { mm}}^{3}$ crystals, enhanced specular reflector (ESR), and barium sulfate (BaSO4) reflector and one LYSO crystal array with $1.88\times 1.88\times 20$ - ${\mathrm { mm}}^{3}$ crystals and $\rm BaSO_{4}$ reflector with dual-ended read out by $8\times 8$ SiPM arrays of $3\times 3$ - ${\mathrm { mm}}^{2}$ active pixel area were measured. Signals of the SiPM arrays were processed individually using 64 channel PETsys TOFPET2 application specific integrated circuits designed for time-of-flight PET applications. For the SiPM arrays, an energy square-weighted average timing method using the timings of the fastest 2 SiPM pixels was found to provide the best-coincidence timing resolutions (CTRs). For the dual-ended readout detectors, the method of using the energy-weighted average timings of the two SiPM arrays provided the best CTR of 234 ps for the detector using $3.10\times 3.10\times 20$ - ${\mathrm { mm}}^{3}$ crystals and ESR reflector, 239 ps for the detector using $3.10\times 3.10\times 20$ - ${\mathrm { mm}}^{3}$ crystals and $\rm BaSO_{4}$ reflector, and 275 ps for the detector using $1.88\times 1.88\times 20$ - ${\mathrm { mm}}^{3}$ crystals and $\rm BaSO_{4}$ reflector for an energy window of 410–610 keV. The dual-ended readout detectors developed in this work provide better CTRs than those of single-ended readout detectors and a high-3-D position resolution which can be used in the future to develop whole-body PET scanners to simultaneously achieve uniform high-spatial resolution, high sensitivity and high-timing resolution.