Geometry optimization and evaluation of PET inserts for simultaneous PET/MR neuroimaging
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Date
2019-08-16
Authors
Teimoorisichani, Mohammadreza
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Abstract
A positron emission tomography (PET) insert with a compact ring diameter is currently under design by our group. The PET insert is a brain-dedicated scanner which is designed to retrofit into the Siemens Magnetom 7T brain Magnetic Resonance (MR) scanner. A dual-layer offset (DLO) design is considered for the detectors of the PET insert to provide depth-of-interaction information and reduce resolution degradation due to parallax error. A wide range of detector geometries was evaluated through Monte Carlo simulations to characterize the performance of each detector and study the optimum detector geometry for the PET insert. More than 200 DLO detectors with a scintillation material of LYSO and detector thicknesses between 10 to 30 mm, different layer thickness ratios and crystal sizes of 0.5 to 4 mm were evaluated in this study. The effects of each detector geometry on radial mispositioning of the incident photons, coincidence response functions, scanner sensitivity and scanner resolution were studied. The effects of layer-misassignment in DLO detectors due to inter-crystal scatter were also studied. The count rate performance of several scanners with different detector sizes and thicknesses were evaluated to provide a comprehensive model for the count rate performance of each scanner with a wide range of deadtime properties. A scalable dual-GPU list-mode image reconstruction algorithm has also been developed, which was used in the evaluation of different brain PET scanners. Based on the results of this work, a single-ended readout DLO detector with an area of between 1.5 to 9.6 cm2, a total/front/back layer thickness of 15/6/9 or 20/8/12 mm, and a crystal size of 2 to 3 mm is recommended.
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Keywords
PET, Positron emission tomography, Statistical image reconstruction, Scintillation detector, Depth-of-interaction, Dual-layer offset