Detector Concepts for Time-of-Flight PET

描述（由申请人提供）：PET成像性能从根本上取决于探测器的性能。近年来，具有良好定时性能的探测器已被各大制造商（飞利浦，西门子，GE）纳入飞行时间（TOF） PET扫描仪，他们将TOF PET/CT仪器作为其顶级产品。这些仪器实现了500-600 ps的TOF分辨率，并通过建立在过去几十年仪器的许多进步，包括高分辨率探测器编码方案，稳定的电子设备，强大的计算机，精确的数据校正和迭代图像重建算法（带建模）用于3D采集，以及用于衰减校正和解剖配准的CT集成，实现了非常好的性能。人们普遍认为，TOF对图像质量产生了影响，并为全身成像提供了临床益处，特别是在肿瘤研究中，病变量化和检测至关重要。虽然时间分辨率和表征临床任务的指标之间的确切关系是复杂的，但可以理解，TOF分辨率的提高应该导致进一步的改善。尽管如此，我们相信改进的时间分辨率将转化为改进的PET成像性能，并可能为临床和研究调查提供进一步的好处。在本研究计划中，我们寻求开发和评估与当今实践中设计相比具有优越时间分辨率的探测器设计。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进行权衡，特别是空间分辨率和灵敏度。事实上，早期的TOF PET扫描仪在20世纪80年代最终被淘汰，因为它们无法与当时传统PET扫描仪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时序性能，但将通过减少视差误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，利用溴化镧闪烁体和硅光倍增器提高定时分辨率；2)探索测量相互作用深度（DOI）的方法，同时保持定时性能；3)开发原型探测器阵列，在适合PET应用的空间分辨率和灵敏度的实际配置中演示改进的定时分辨率。4)利用计算机模型和临床成像指标（如病变对比和可检测性）说明改进的检测器的影响。在这个项目的结论中，我们将开发并表征一种新的探测器，该探测器将快速闪烁体与固态光传感器相结合，具有改进的TOF PET性能。

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.