Improved PET Timing Resolution: Feasibility and Value

描述（由申请人提供）： 该项目将证明，通过使用基于LSO的PET相机的飞行时间（TOF）信息，可以将研究时间或注射剂量减少多达5倍。这种减少将是可实现的，在临床上，全身图像与PET相机，从现有的商业相机几乎没有什么不同。因此，这一发展的潜在影响很大，特别是对肿瘤学。飞行时间PET在20世纪80年代被广泛研究，并且噪声性能的改善得到了很好的证明。TOF研究在20世纪90年代死亡，因为能够执行TOF测量的闪烁体材料所造成的妥协超过了TOF的优势。从那时起，一种新的闪烁体材料（LSO）被发现，现在被纳入许多商业PET扫描仪。LSO没有以前的TOF延迟器的缺点，并且在实验室情况下已经实现了300 ps的fwhm定时分辨率。这种定时精度将很容易实现TOF PET。其他因素，如光电倍增管的改进和定制集成电路的进步，使TOF PET在今天更加实用。因此，很可能在基于LSO的商业PET相机中可以实现500 ps的定时分辨率，这将在全身成像中将噪声方差降低5倍。在临床上，这种方差减小可以减少图像噪声，减少注射剂量，缩短成像时间，或提供这三种益处的组合。本提案中的任务将证明，商业PET扫描仪的定时分辨率可以得到足够的改善，以实现TOF。我们将首先量化的组件/因素，限制商业基于LSO的PET相机，如光电倍增管中的渡越时间抖动，闪烁晶体内的反射，和时间测量电子器件（常数分数鉴别器和时间-数字转换器电路）的性能的符合定时分辨率的定时分辨率。接下来，我们将设计、构造和表征那些最降低时序分辨率的项目的替换组件。我们将使用这些新开发的组件来演示，与八个探测器模块原型，可以在商业系统中实现的定时分辨率。最后一项任务是量化测量的飞行时间分辨率将给执行全身FDG研究的现代PET相机带来的增益。将使用2-D和3-D TOF重建算法进行量化，并将量化噪声和空间分辨率的改善。

DESCRIPTION (provided by applicant): This project will demonstrate that study time or injected dose can be reduced by a factor of up to 5 by using time-of-flight (TOF) information with LSO-based PET cameras. This reduction would be achievable in clinical, whole body images obtained with PET cameras that differ little from existing commercial cameras. Therefore, the potential impact of this development is large, especially for oncology. Time-of-flight PET was extensively studied in the 1980's and the improvement in noise performance well documented. TOF research died in the 1990's, as compromises caused by the scintillator materials capable of performing TOF measurements outweighed the TOF advantages. Since then, a new scintillator material (LSO) has been discovered and is now being incorporated into many commercial PET scanners. LSO does not have the disadvantages of previous TOF scintillators, and has achieved 300 ps fwhm timing resolution in laboratory situations. This timing accuracy would easily enable TOF PET. Other factors, such as improvements in photomultiplier tubes and advances in custom integrated circuits, make TOF PET much more practical to achieve today. Therefore, it is very likely that 500 ps timing resolution could be achieved in commercial LSO-based PET cameras, which would reduce the noise variance by a factor of 5 in whole body imaging. Clinically, this variance reduction could reduce image noise, decrease the injected dose, shorten the imaging time, or provide a combination of these three benefits. The tasks in this proposal will demonstrate that the timing resolution in commercial PET scanners can be improved enough to enable TOF. We will first quantify the timing resolution of the components/factors that limit the coincidence timing resolution in commercial LSO-based PET cameras, such as transit time jitter in the photomultiplier tubes, reflections within the scintillator crystals, and performance of the time measurement electronics (constant fraction discriminators and time-to-digital converter circuits). Next we will design, construct, and characterize replacement components for those items that most degrade the timing resolution. We will use these newly developed components to demonstrate, with an eight detector module prototype, the timing resolution that could be achieved in a commercial system. The final task is to quantify the gains that the measured time-of-flight resolution would bring to a modern PET camera performing a whole-body FDG study. The quantification will be done using both 2-D and 3-D TOF reconstruction algorithms and will quantify the improvement in noise and spatial resolution.