Optical Barriers to Improve Performance of a Continuous Detector for Clinical PET

描述(申请人提供)：近年来，各大制造商已将具有非常好的空间、能量和时间分辨率以及高灵敏度的探测器集成到商用PET/CT扫描仪中。这些仪器使用探测器模块，或将LSO/LYSO闪烁晶体合并为像素化设计的模块，以便像素的横截面(通常为4 x 4-mm2)确定空间分辨率。使用NaI(Tl)的连续闪烁探测器已用于PET多年，但由于其相对较低的阻止能力和较长的衰减时间，其性能不能与2000年初S在PET扫描仪中引入的LSO/LYSO相比。本研究方案旨在开发一种连续LYSO探测器块，以利用这种材料的良好性能，但具有连续探测器的优点。与像素化探测器块相比，我们期望连续探测器对晶体块内的所有相互作用具有非常均匀的光采样，这导致了优异的空间、能量和时间分辨率性能。与像素化探测器相比，在制造连续块探测器方面也存在潜在的成本节约，特别是对于需要高空间分辨率的设计。在系统层面上，具有连续定位的探测器能够改进空间和角度采样(没有探测器运动或摆动)，从而改进图像重建。此外，连续探测器的设计适合于相互作用深度(DOI)的测量，这可用于减小系统视差误差。在厚度足以达到高灵敏度的连续块探测器中，要获得优异的空间分辨率，关键是控制来自伽马相互作用部位的光的传播。耦合到闪烁体的一个表面的光电探测器测量闪烁光子的信噪比取决于光响应函数(LRF)并确定探测器的分辨率。这项研究的重点是开发和评估通过将激光诱导光障(LIOB)技术应用于我们的连续闪烁晶体块来提高LRF的方法。已经证明在LYSO晶体中可以产生LIOB，因此，我们工作的目标是确定如何利用这一技术在厚的、连续的晶体中获得最佳的LRF。横向连续位置采样和DOI信息的结合将提高临床PET的性能。我们的具体目标是1)表征连续闪烁晶体中激光诱导光障的行为，2)开发一个计算机模型来优化闪烁晶体中的光响应函数，从而提高空间分辨率并实现相互作用深度测量，以及3)测试优化布置激光诱导光障的连续闪烁探测器的性能。

DESCRIPTION (provided by applicant): In recent years detectors with very good spatial, energy, and timing resolution, as well as high sensitivity, have been incorporated into commercial PET/CT scanners by each of the major manufacturers. These instruments use detector blocks, or modules that incorporate LSO/LYSO scintillation crystals in a pixelated design, such that the cross-section of the pixel, typically 4 x 4-mm2, determines the spatial resolution. Continuous scintillation detectors using NaI (Tl) were used in PET for many years, but due to its relatively low stopping power and long decay time it could not provide competitive performance compared to LSO/LYSO introduced in PET scanners in the early 2000's. This research proposal seeks to develop a continuous LYSO detector block to take advantage of the favorable properties of this material, but with the advantages of a continuous detector. Compared to a pixelated detector block, we expect a continuous detector to have very uniform light sampling for all interactions within the crystal block, which leads to excellent performance of spatial, energy, and timing resolution. There are also potential cost savings in manufacturing a continuous block detector compared to a pixelated detector, particularly for designs required high spatial resolution. On a system level, a detector with continuous positioning enables improved spatial and angular sampling (without detector motion or wobbling), which leads to improved image reconstruction. Further, a continuous detector design lends itself to measurement of depth-of-interaction (DOI), which can be used to reduce the system parallax error. The key to excellent spatial resolution in a continuous block detector, which is thick enough to achieve high sensitivity, is to control the spread of light from the site of gamma interaction. The signal-to-noise of the measurement of scintillation photons by the photo-detectors, coupled to one surface of the scintillator, is dependent on the light response function (LRF) and determines the resolution of the detector. The focus of this research proposal is to develop and evaluate the methodology to improve the LRF by applying the technology of laser induced optical barriers (LIOB) to our continuous scintillation crystal blocks. It has been demonstrated that LIOBs can be created in LYSO crystals, therefore, the goal of our work is to determine how to utilize this technology to achieve an optimal LRF in a thick, continuous crystal. The combination of continuous position sampling in the transverse direction and DOI information will improve performance for clinical PET. Our specific aims are 1) characterize the behavior of laser induced optical barriers in continuous scintillation crystals, 2) develop a computer model to optimize the light response function in the scintillation crystal so as to improve spatial resolution and enable depth-of-interaction measurements, and 3) test the performance of a continuous scintillation detector with optimized arrangement of laser induced optical barriers.