Study of optical reflectors for a 100ps coincidence time resolution TOF-PET detector design.
Study of optical reflectors for a 100ps coincidence time resolution TOF-PET detector design.
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DOI：
10.1088/2057-1976/ac240e
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发表时间：
2021-09-15
影响因子：
1.4
通讯作者：
Levin CS
中科院分区：
文献类型：
--
作者：
Gonzalez-Montoro A;Pourashraf S;Lee MS;Cates JW;Levin CS
正电子发射断层成像(PET)重建图像的信噪比(SNR)可以通过包含511keV光子对符合飞行时间(TOF)信息来提高。这种TOF能力对SNR的改善程度取决于PET系统的符合时间分辨率(CTR)，CTR本质上是对放置在系统中心的点正电子源检测到的所有符合光子对的光子到达时间差的变化。CTR由几个因素决定，包括闪烁晶体和光电探测器的本征性质、晶体-光电探测器耦合配置、反射材料和电子读出配置方案。本工作的目标是建立一种新型的TOF-PET系统，其CTR为100皮秒(PS)，与达到225-400ps CTR的最先进的TOF-PET系统相比，重建图像的SNR额外提高了1.5-2.0倍。要了解的一个关键参数是光学反射器对闪烁光收集和光电探测器的渡越时间变化的影响。为了研究覆盖在闪烁晶体元件上的反射器对CTR的影响，我们测试了四种不同的反射器材料的性能：增强型镜面反射器(ESR)--在闪烁体上加上空气或光学润滑脂；特氟隆胶带；BaSO4涂料单独或与环氧树脂混合；以及二氧化钛涂料。在实验装置中，我们使用了3×3×10 mm~3的FAST-LGSO：Ce闪烁晶体元件耦合到一组硅光电倍增管(SiPM)上，采用了一种新的“侧面读出”结构，该结构已被证明在闪烁光收集效率和到光电探测器的渡越时间方面具有较低的变化。结果表明，四种涂层的CTR值分别为102.0±0.8、100.2±1.2、97.3±1.8和95.0±1.0ps，未校准的能量分辨率分别为10.2±1.8、9.9±1.2、7.9±1.2和8.6±1.7%。
Positron Emission Tomography (PET) reconstructed image signal-to-noise ratio (SNR) can be improved by including the 511 keV photon pair coincidence time-of-flight (TOF) information. The degree of SNR improvement from this TOF capability depends on the coincidence time resolution (CTR) of the PET system, which is essentially the variation in photon arrival time differences over all coincident photon pairs detected for a point positron source placed at the system center. The CTR is determined by several factors including the intrinsic properties of the scintillation crystals and photodetectors, crystal-to-photodetector coupling configurations, reflective materials, and the electronic readout configuration scheme. The goal of the present work is to build a novel TOF-PET system with 100 picoseconds (ps) CTR, which provides an additional factor of 1.5–2.0 improvement in reconstructed image SNR compared to state-of-the-art TOF-PET systems which achieve 225 – 400 ps CTR. A critical parameter to understand is the optical reflector’s influence on scintillation light collection and transit time variations to the photodetector. To study the effects of the reflector covering the scintillation crystal element on CTR, we have tested the performance of four different reflector materials: Enhanced Specular Reflector (ESR) –coupled with air or optical grease to the scintillator; Teflon tape; BaSO4 paint alone or mixed with epoxy; and TiO2 paint. For the experimental set-up, we made use of 3×3×10 mm3 fast-LGSO:Ce scintillation crystal elements coupled to an array of silicon photomultipliers (SiPMs) using a novel “side-readout” configuration that has proven to have lower variations in scintillation light collection efficiency and transit time to the photodetector. Results show CTR values of 102.0±0.8, 100.2±1.2, 97.3±1.8 and 95.0±1.0 ps full-width-half-maximum (FWHM) with non-calibrated energy resolutions of 10.2±1.8, 9.9±1.2, 7.9±1.2, and 8.6±1.7 % FWHM for the Teflon, ESR (without grease), BaSO4 (without epoxy) and TiO2 paint treatments, respectively.
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