用于脑专用 PET 扫描仪的双层偏移闪烁体阵列中的晶间散射研究。

Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada. Author to whom any correspondence should be addressed.

Phys Med Biol. 2019 May 23;64(11):115007. doi: 10.1088/1361-6560/ab1503.

A dual-layer offset (DLO) detector enables depth-of-interaction (DOI) through light sharing between two layers of scintillation arrays with a single-ended readout (SER) scheme. However, the SER scheme in DLO detectors may lead to a layer misassignment when inter-crystal scattering occurs. The aim of this work is to study inter-crystal scattering and evaluate the effects of layer misidentifications in DLO detectors on the performance of scanners suitable for a brain-dedicated PET insert. The influence of layer misidentification on the coincidence response functions (CRFs) of 3 different DLO detectors with total/front/back layer thicknesses of 15/6/9 mm, 20/8/12 mm, and 25/7.5/17.5 mm and a crystal width of about 3 mm was studied through Monte Carlo simulations. To overcome layer misidentification, we studied a practical DLO detector design in which each layer can be read out independently through a discrete-layer readout (DLR) scheme where light sharing between the layers is avoided. The CRFs of the mentioned DLO detectors assuming SER and DLR were analyzed. To evaluate the effects of layer misidentification on image quality, images of a Derenzo-like phantom were also reconstructed for all DLO and their equivalent single layer PET scanners. Our analysis showed that layer misassignments due to inter-crystal scatter in DLO detectors mainly has effect on the full-width at tenth maximum of the CRFs. According to the reconstructed images of the phantom, no significant improvements in the quality of the images were seen when SER was replaced with DLR. The results suggest that layer misidentification in DLO detectors does not play an important role in the quality of the PET images.

双层偏移（DLO）探测器通过在单个端接读取（SER）方案中使用两层闪烁体阵列之间的光共享来实现相互作用深度（DOI）。然而，在 DLO 探测器中，当晶体内散射发生时，SER 方案可能导致层分配错误。本工作旨在研究晶体内散射，并评估 DLO 探测器中层错误识别对适用于脑专用 PET 插件的扫描仪性能的影响。通过蒙特卡罗模拟研究了总/前/后层厚度分别为 15/6/9mm、20/8/12mm 和 25/7.5/17.5mm 以及晶体宽度约为 3mm 的 3 种不同 DLO 探测器的层错误识别对符合响应函数（CRF）的影响。为了克服层错误识别，我们研究了一种实用的 DLO 探测器设计，其中每个层都可以通过避免层之间光共享的离散层读取（DLR）方案独立读取。分析了所提到的 DLO 探测器在 SER 和 DLR 下的 CRF。为了评估层错误识别对图像质量的影响，还对所有 DLO 及其等效单层 PET 扫描仪的 Derenzo 样体模图像进行了重建。我们的分析表明，DLO 探测器中的晶体内散射引起的层分配错误主要对 CRF 的第十个最大值的全宽有影响。根据体模的重建图像，当 SER 被 DLR 取代时，图像质量没有明显改善。结果表明，DLO 探测器中的层错误识别在 PET 图像质量中不起重要作用。