Digital PET involving silicon photomultipliers (SiPM) provides an enhanced time-of-flight (TOF) resolution as compared with photomultiplier (PMT)-based PET, but also a better prevention of the count-related rises in dead time and pile-up effects mainly due to smaller trigger domains (i.e., the detection surfaces associated with each trigger circuit). This study aimed to determine whether this latter property could help prevent against deteriorations in TOF resolution and TOF image quality in the wide range of PET count rates documented in clinical routine. Variations, according to count rates, in timing resolution and in TOF-related enhancement of the quality of phantom images were compared between the first fully digital PET (Vereos) and a PMT-based PET (Ingenuity). Single-count rate values were additionally extracted from the list-mode data of routine analog- and digital-PET exams at each 500-ms interval, in order to determine the ranges of routine PET count rates. Routine PET count rates were lower for the Vereos than for the Ingenuity. For Ingenuity, the upper limits were estimated at approximately 21.7 and 33.2 Mcps after injection of respectively 3 and 5 MBq.kg-1 of current 18F-labeled tracers. At 5.8 Mcps, corresponding to the lower limit of the routine count rates documented with the Ingenuity, timing resolutions provided by the scatter phantom were 326 and 621 ps for Vereos and Ingenuity, respectively. At higher count rates, timing resolution was remarkably stable for Vereos but exhibited a progressive deterioration for Ingenuity, respectively reaching 732 and 847 ps at the upper limits of 21.7 and 33.2 Mcps. The averaged TOF-related gain in signal/noise ratio was stable at approximately 2 for Vereos but decreased from 1.36 at 5.8 Mcps to 1.14 and 1.00 at respectively 21.7 and 33.2 Mcps for Ingenuity. Contrary to the Ingenuity PMT-based PET, the Vereos fully digital PET is unaffected by any deterioration in TOF resolution and consequently, in the quality of TOF images, in the wide range of routine PET count rates. This advantage is even more striking with higher count-rates for which the preferential use of digital PET should be further recommended (i.e., dynamic PET recording, higher injected activities).

中文翻译：

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全数字PET不受常规PET计数率范围内TOF分辨率和TOF图像质量的任何下降的影响

与基于光电倍增管（PMT）的PET相比，涉及硅光电倍增管（SiPM）的数字PET提供了更高的飞行时间（TOF）分辨率，而且可以更好地防止与计数有关的死区时间和堆积效应主要是由于较小的触发域（即与每个触发电路关联的检测表面）。这项研究旨在确定在临床常规记录的各种PET计数率范围内，后一种特性是否可以帮助防止TOF分辨率和TOF图像质量的下降。在第一个全数字PET（Vereos）和基于PMT的PET（Ingenuity）之间，比较了根据计数率，时序分辨率和幻影图像质量在TOF相关增强方面的变化。每隔500毫秒间隔从常规模拟和数字PET检查的列表模式数据中另外提取单计数率值，以确定常规PET计数率的范围。Vereos的常规PET计数率低于Ingenuity。对于Ingenuity，在分别注射3和5 MBq.kg-1的当前18F标记示踪剂后，估计上限约为21.7和33.2 Mcps。在5.8 Mcps的速度下，对应于Ingenuity记录的常规计数率的下限，散射体模为Vereos和Ingenuity提供的定时分辨率分别为326 ps和621 ps。在较高的计数率下，Vereos的定时分辨率非常稳定，但Ingenuity却逐渐恶化，在21的上限处分别达到732和847 ps。7和33.2 Mcps。对于Vereos，与TOF相关的平均信噪比增益稳定在大约2，但从5.8 Mcps的1.36降低到分别为21.7和33.2 Mcps的Incomuity的1.14和1.00。与基于Ingenuity PMT的PET相比，Vereos全数字PET不受TOF分辨率下降的影响，因此，在各种常规PET计数率范围内，TOF图像的质量也不会受到影响。更高的计数率时，这一优势更为显着，应进一步建议优先使用数字PET（例如，动态PET记录，较高的注射活性）。与基于Ingenuity PMT的PET相比，Vereos全数字PET不受TOF分辨率下降的影响，因此，在各种常规PET计数率范围内，TOF图像的质量也不会受到影响。更高的计数率时，这一优势更为显着，应进一步建议优先使用数字PET（例如，动态PET记录，较高的注射活性）。与基于Ingenuity PMT的PET相比，Vereos全数字PET不受TOF分辨率下降的影响，因此，在各种常规PET计数率范围内，TOF图像的质量也不会受到影响。更高的计数率时，这一优势更为显着，应进一步建议优先使用数字PET（例如，动态PET记录，较高的注射活性）。