Detector Concepts for Time-of-Flight PET

描述（由申请人提供）：PET成像性能基本上依赖于探测器的性能。近年来，具有非常好的定时性能的探测器已经被每个主要制造商（Philips、Siemens、GE）并入飞行时间（TOF）PET扫描仪中，这些制造商将TOF PET/CT仪器作为其顶级产品来推广。这些仪器实现了500-600 ps TOF分辨率，并通过建立在过去几十年仪器的许多进步基础上实现了非常好的性能，包括高分辨率探测器编码方案、稳定的电子设备、功能强大的计算机、用于3D采集的精确数据校正和迭代图像重建算法（具有建模），以及用于衰减校正和解剖配准的CT集成。人们普遍认为TOF对图像质量产生了影响，并且它为全身成像提供了临床益处，特别是病变量化和检测至关重要的肿瘤学研究。应当理解，改进的TOF分辨率应导致进一步的改进，尽管时序分辨率和表征临床任务的度量之间的确切关系是复杂的。尽管如此，我们相信改进的定时分辨率将转化为改进的PET成像性能，并且可能为临床和研究调查提供进一步的益处。在这项研究建议中，我们寻求开发和评估的检测器设计相比，在实践中的设计具有上级定时分辨率。我们确实认识到，改进的探测器定时分辨率必须与探测器性能的其他因素，特别是空间分辨率和灵敏度进行权衡。事实上，20世纪80年代的早期TOF PET扫描仪最终被淘汰，因为它们无法与当时传统PET扫描仪的更好的空间分辨率和更高的灵敏度竞争。因此，我们将考虑改进的定时分辨率以及其他检测器性能指标对系统整体性能的影响。我们还将开发一种TOF设计，其中还包括区分交互深度（DOI）的能力。这种设计可能会牺牲最终的定时性能，但会通过减少视差来提高系统的空间分辨率，并允许设计具有较小环形几何形状的全身系统。具体目标包括：1）开发探测器概念，以提高溴化镧闪烁器和硅光电倍增器的定时分辨率，2）探索测量相互作用深度（DOI）的方法，同时还保持定时性能，3）开发原型探测器阵列，以证明在具有适合PET应用的空间分辨率和灵敏度的实际配置中改进的定时分辨率，以及4）示出了使用计算机模型和临床成像度量（例如病变对比度和可检测性）的改进的检测器的影响。在这个项目的结论，我们将开发和表征一个新的探测器与TOF PET的性能提高，结合快速闪烁器与固态光电传感器。

DESCRIPTION (provided by applicant): PET imaging performance fundamentally relies on the performance of the detector. In recent years detectors with very good timing performance have been incorporated into time-of-flight (TOF) PET scanners by each of the major manufacturers (Philips, Siemens, GE) who promote TOF PET/CT instruments as their top-of-the-line products. These instruments achieve 500-600 ps TOF resolution, and achieve very good performance by building upon many advances in instrumentation from the last decades, including high-resolution detector encoding schemes, stable electronics, powerful computers, accurate data correction and iterative image reconstruction algorithms (with modeling) for 3D acquisition, and integration of CT for attenuation correction and anatomic registration. It is widely held that TOF has made an impact on image quality and that it provides a clinical benefit for whole-body imaging, in particular oncology studies where lesion quantification and detection are critical. It is understood that improved TOF resolution should lead to further improvements, although the exact relationship between timing resolution and metrics to characterize clinical tasks is complicated. Nevertheless, we believe that improved timing resolution will translate to improved PET imaging performance, and is likely to provide further benefit for both clinical and research investigations. In this research proposal we seek to develop and evaluate a detector design with superior timing resolution compared to designs in practice today. We do recognize that improved detector timing resolution must be weighed against other factors of detector performance, in particular spatial resolution and sensitivity. In fact, early TOF PET scanners in the 1980's were eventually phased out since they could not compete against the better spatial resolution and higher sensitivity of conventional PET scanners at the time. Therefore, we will consider the impact of improved timing resolution together with other detector performance metrics on the overall performance of the system. We will also develop a design for TOF that also includes the ability to discriminate depth-of-interaction (DOI). This design may trade-off ultimate timing performance, but will improve system spatial resolution by reducing parallax error, and allow for the design of whole-body systems with smaller ring geometry. The specific aims include 1) develop detector concepts to improve timing resolution with lanthanum bromide scintillators and silicon photo-multipliers, 2) explore ways to measure depth-of-interaction (DOI) while also preserving timing performance, 3) develop proto-type detector arrays to demonstrate improved timing resolution in a practical configuration with spatial resolution and sensitivity appropriate for PET applications, and 4) illustrate the impact of improved detectors using computer models and clinical imaging metrics, such as lesion contrast and detectability. At this project's conclusion we will have developed and characterized a new detector with improved performance for TOF PET that combines fast scintillators with solid-state photosensors.