Performance evaluation of the mindview PET using GATE and STIR

A series of small size
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Na point sources have been simulated using GATE, following the NEMA protocol, and applied to the geometry of a brain dedicated PET so-called MindView. The simulated scanner geometry is currently composed by one ring of 20 detector blocks with a distance of about 330 mm between opposite detectors. Each detector module includes a monolithic LYSO crystal of 50 × 50 × 20 mm
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and a custom 12 × 12 SiPM array (TSV-type, SensL). The system defines an axial and trans-axial fields of view (FoV) of about 46 mm and 240 mm, respectively. The scintillation light inside the monolithic block was simulated in GEANT4 and is sampled following the readout scheme providing information on each SiPM array row and column (12 + 12). Out of this, three different approaches for the determination of the impact coordinates within the monolithic crystals have been considered. A first approach makes use of the center of gravity (CoG) calculation for the planar XY coordinates but the photon impact depth of interaction (DoI) is not considered. The other methods obtain the XY coordinates using the Raise to Power algorithm (RTP) before CoG calculation, with both discrete (second method) and continuous (third one) DoI information. The data is introduced on the STIR platform for reconstruction using a filtered back projection 3D re-projected algorithm (FBP3DRP). Spatial resolutions ranging in the intervals [2 mm, 3.4 mm], [2.3 mm, 3.3mm] and [2.2 mm, 2.3 mm] have been obtained for the radial, tangential and axial directions, respectively. The points sources were positioned at a radial offset of 100 mm radially out of the center.