Development and validation of an accurate GATE model for NeuroPET scanner

NeuroPET is a cylindrical full ring mobile PET/CT scanner for brain imaging that was developed by Photo Diagnostic Systems, Inc. The scanner has 7 modules, each with 3 × 4 detector blocks. The detectors have two layers of scintillator arrays with a half pixel pitch offset to realize two levels of depth of interaction. In this study, we evaluated the NeuroPET scanner modeled in the GATE simulation tool and analyzed the acquired data to better understand the contribution of inter-detector scattering (IDS). The results show that the average difference between simulated and measured data for a point-like source is 2.5%. The differences are 4.7% and 2.7% for NEMA line source in two data acquisition modes and 5.5% for peak NECR measurement. IDS evaluation indicated that the total fractions of the cross-layer crystal scatter (CLCS) and inter-layer crystal scatter (ILCS) events in singles detection mode are 1.98% and 7.98%, respectively. Approximately 90% of these CLCS events deposit most of their energy in the crystal layer other than the layer of first interaction. Additionally, no significant difference in ILCS fractions between the two layers (8.05% vs 7.35%) was observed. The simulation results demonstrate that ILCS events account for ∼79% of the total mis-positioned events.