量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Positron emission tomography (PET) has become a popular imaging method in metabolism, neuroscience, and molecular imaging. For dedicated human brain and small animal PET scanners, high spatial resolution is needed to visualize small objects. To improve PET resolution, we are developing X'tal cube, which is our new PET detector to achieve isotropic 3D positioning detectability. It consists of a segmented 3D crystal block of which all surfaces are covered with semiconductor photo-sensors. We have shown that the X'tal cube can achieve (1 mm)3 uniform crystal identification performance. To improve further spatial resolution, we intend to develop the sub-millimeter X'tal cube. However, one problem that prevents its commercial mass production is handling the small crystal pieces, i.e., cutting out and assembling them. In this work, to evaluate to benefit of the sub-millimeter X'tal cube, we simulated dedicated brain and small animal PET scanners with X'tal cubes using a Monte Carlo simulation and calculated spatial resolutions with the X'tal cubes with from (0.5 mm)3 to (1.0 mm)3 cubic crystals. For spatial resolution evaluation, a point source emitting 511 keV photons was simulated with all physical processes involved during emission and interaction of positrons. The brain PET scanner has a detector ring of 275 mm in diameter composed of 48 detectors. The small animal PET scanner has a detector ring of 82 mm in diameter composed of 14 detectors. The simulated data were projected to the sinogram and reconstructed using the 2D filtered backprojection. For the small animal PET scanner, we showed that sub-millimeter spatial resolution is possible using the X'tal cube with cubic crystals smaller than 0.9 mm even with the physical processes. On the other hand, for the brain PET scanner, spatial resolutions increased 20% larger than these of the small animal PET scanner due to the non-collinearity effect. However, for both PET scanners, we showed that the spatial resolution significantly improved, as cubic crystals were smaller.
Design Study of the DOI-PET Scanners with the X'tal Cubes Toward Sub-Millimeter Spatial Resolution
