Initial Performance of a Prototype Small Animal PET Scanner Consisting of Long Semi-Monolithic Scintillator Detectors

Semi-monolithic scintillator detectors possess not only the inherent depth of interaction (DOI) encoding capability of monolithic scintillator detectors but also reduced edge effects compared to monolithic scintillator detectors. The performance of a small animal PET scanner consisting of long semi-monolithic scintillator detectors was investigated in this work. Two semi-monolithic scintillator detectors composed of 12 LYSO slabs of 0.96 × 56 × 10 mm³ with ESR or BaSO₄ as the reflectors were manufactured. First, a prototype small animal PET scanner consisting of the two semi-monolithic detectors and a rotation platform was built. The spatial resolution of the prototype PET scanner was measured using a ²²Na point source. Second, the sensitivity and imaging performance of a full-ring small animal PET scanner consisting of 20 semi-monolithic detectors was simulated using GATE software. The proposed position calibration method for semi-monolithic scintillator detectors effectively addressed non-uniform position responses in both the monolithic and DOI directions and was suitable for system-level PET scanner calibration. Using experimental data from the two-detector prototype PET scanner, spatial resolution better than 0.65 mm was obtained with point spread function (PSF) modelling. In Monte Carlo simulations of a full-ring PET scanner consisting of 20 such detectors, a peak sensitivity of 5.45% was achieved, and rods with a diameter of 0.75 mm were clearly resolved in phantom images reconstructed with PSF modelling. Long semi-monolithic scintillator detector represents a promising candidate for developing small animal PET systems to achieve sub-millimeter uniform spatial resolution, good sensitivity, and reduced cost.