一种使用时间超越阈值的数字磷光体探测器，用于 PET 中的相互作用深度。

A digital phoswich detector using time-over-threshold for depth of interaction in PET.

机构信息

Crump Institute for Molecular Imaging, David Geffen School of Medicine, University of California, Los Angeles, CA, United States of America.

Shared first authorship.

出版信息

Phys Med Biol. 2020 Dec 15;65(24):245017. doi: 10.1088/1361-6560/abcb21.

DOI:10.1088/1361-6560/abcb21

PMID:33202397

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC8382115/

Abstract

We present the performance of a digital phoswich positron emission tomography (PET) detector, composed by layers of pixilated scintillator arrays, read out by solid state light detectors and an application specific integrated circuit (ASIC). We investigated the use of integrated charge from the scintillation pulses along with time-over-threshold (ToT) to determine the layer of interaction (DOI) in the scintillator. Simulations were performed to assess the effectiveness of the ToT measurements for separating the scintillator events and identifying cross-layer-crystal-scatter (CLCS) events. These simulations indicate that ToT and charge integration from such a detector provide sufficient information to determine the layer of interaction. To demonstrate this in practice, we used a pair of prototype LYSO/BGO detectors. One detector consisted of a 19 × 19 array of 7 mm long LYSO crystals (1.36 mm pitch) coupled to a 16 × 16 array of 8 mm long BGO crystals (1.63 mm pitch). The other detector was similar except the LYSO crystal pitch was 1.63 mm. These detectors were coupled to an 8 × 8 multi-pixel photon counter mounted on a PETsys TOFPET2 ASIC. This high performance ASIC provided digital readout of the integrated charge and ToT from these detectors. We present a method to separate the events from the two scintillator layers using the ToT, and also investigate the performance of this detector. All the crystals within the proposed detector were clearly resolved, and the peak to valley ratio was 11.8 ± 4.0 and 10.1 ± 2.9 for the LYSO and BGO flood images. The measured energy resolution was 9.9% ± 1.3% and 28.5% ± 5.0% respectively for the LYSO and BGO crystals in the phoswich layers. The timing resolution between the LYSO-LYSO, LYSO-BGO and BGO-BGO coincidences was 468 ps, 1.33 ns and 2.14 ns respectively. Results show ToT can be used to identify the crystal layer where events occurred and also identify and reject the majority of CLCS events between layers.

摘要

我们展示了一种由像素化闪烁体阵列层组成的数字正电子发射断层扫描（PET）探测器的性能，该探测器由固态光探测器和专用集成电路（ASIC）读取。我们研究了利用闪烁脉冲的积分电荷和过阈值时间（ToT）来确定闪烁体中的相互作用层（DOI）。进行了模拟以评估 ToT 测量在分离闪烁体事件和识别跨层晶体散射（CLCS）事件方面的有效性。这些模拟表明，来自这种探测器的 ToT 和电荷积分提供了足够的信息来确定相互作用层。为了在实践中证明这一点，我们使用了一对原型 LYSO/BGO 探测器。一个探测器由一个 19×19 阵列的 7 毫米长 LYSO 晶体（1.36 毫米间距）组成，耦合到一个 16×16 阵列的 8 毫米长 BGO 晶体（1.63 毫米间距）。另一个探测器除了 LYSO 晶体间距为 1.63 毫米外，其余均相同。这些探测器与安装在 PETsys TOFPET2 ASIC 上的 8×8 多像素光子计数器相连。这种高性能 ASIC 提供了来自这些探测器的集成电荷和 ToT 的数字读出。我们提出了一种使用 ToT 从两个闪烁体层中分离事件的方法，并研究了该探测器的性能。在所提出的探测器内的所有晶体都被清晰地分辨出来，LYSO 和 BGO 洪水图像的峰谷比分别为 11.8 ± 4.0 和 10.1 ± 2.9。在正电子发射断层扫描层中，LYSO 和 BGO 晶体的测量能量分辨率分别为 9.9%±1.3%和 28.5%±5.0%。LYSO-LYSO、LYSO-BGO 和 BGO-BGO 之间的定时分辨率分别为 468 ps、1.33 ns 和 2.14 ns。结果表明，ToT 可用于识别发生事件的晶体层，并识别和拒绝层间的大多数 CLCS 事件。