A dual layer fast timing detector for time-of-flight PET

This work presents the design of scintillation detectors for clinical PET using off-the-shelf components that achieve both excellent time resolution and DoI information. The detector consists of a dual layer stack of 3×3×20 mm³ crystals, 1:1 coupled to SiPM arrays. Each pixel contains an LYSO:Ce and LSO:Ce,Ca(0.4%) crystal directly bonded to one another with an optical epoxy, and layer identification was performed via pulse shape discrimination. Layer interaction discrimination was explored through parameterization of crystal orientation, reflector and coupling materials, SiPM selection, and preamplifier choice - as all these affect pulse shape discrimination capabilities. The final design selection achieved a layer identification identification error rate of 9%. The achievable coincidence timing resolution between two identical two-layer detectors was found to be 224 ps FWHM. Layer-gated coincidence timing resolutions of 222 and 220 ps FWHM were measured for LSO:Ce,Ca(0.4%) and LYSO:Ce in coincidence with the same layers on an identical detector. The detector design has been integrated into a data acquisition system to assess imaging performance with this design.