High-resolution PET detector with 100 ps coincidence time resolution using side-by-side phoswich design

We propose a new high-resolution TOF PET detector, a "side-by-side phoswich detector", where two crystals with fast and slow decay time are side-coupled to a row of photosensors. Monte Carlo simulation was conducted to find the optimal conditions for a side-by-side phoswich design. Then a proof-of-concept PET detector was built comprising two 1.9×1.9×10 mm
³
LSO crystals (τ_d=34.39 and 43.07 ns) sidecoupled with three 4×4 mm
²
SensL SiPMs. A CTR of 107.07 ps was achieved at 32V bias voltage with a 2 mV leading edge threshold for the side-by-side phoswich configuration. The side-by-side phoswich detector showed good energy resolution of 10.35% at 511 keV and good crystal separation in two 1.9×1.9×10 mm
³
crystals with different decay time when we applied the time-over-threshold technique. These results indicate we can achieve high resolution, 10% energy resolution and 100-ps coincidence timing resolution (CTR) all at once.