DEPTH OF INTERACTION MEASUREMENT IN ANGER CAMERAS

几家商业公司最近推出了双头愤怒相机系统，该系统既能进行巧合光子成像，也能进行单光子成像。这些系统可能有潜力成为许多社区医院专用正电子发射断层扫描（PET）系统的替代方案。然而，这些系统的符合成像性能，在系统灵敏度和空间分辨率方面，目前明显低于最先进的专用PET系统。为了提高符合成像的整体检测效率，厚的NaI（Tl）晶体被用于这些多用途系统中。不幸的是，当双anger相机系统在重合成像模式下工作时，厚晶体会增加视差误差，从而降低重建图像的分辨率；厚晶体也会降低固有的空间分辨率性能，特别是在成像低能量单光子示踪剂时。如果测量到的伽马射线的相互作用深度（DOI），视差误差的影响可以最小化。此外，我们认为相同的DOI信息可以用于提高内在空间分辨率。我们提出了一种利用移波长（WLS）闪烁光纤，以线性阵列耦合到大面积NaI（Tl）晶体的入口面来测量Anger相机DOI的方法的可行性。我们假设闪烁光纤测量的光输出分布随DOI的变化而变化：随着相互作用位置离入口面越远，分布的宽度越宽。在这项研究中，我们将开发使用WLS闪烁光纤进行DOI测量所需的硬件和软件，特别是用于商业多用途双头Anger相机系统中使用的厚大面积NaI（Tl）晶体。我们将评估我们的方法的能力，以减少视差误差在符合成像。我们还将研究在三维线性校正技术中获得的DOI信息的潜在用途，以提高Anger相机的平面固有空间分辨率。

Several commercial companies have recently introduced dual-head Anger camera systems capable of both coincidence-photon and single-photon imaging. These systems may have the potential to be an alternative to dedicated positron emission tomography (PET) systems for many community hospitals. However, the coincidence-imaging performance of these systems, in terms of system sensitivity and spatial resolution, currently falls significantly short of that of dedicated state-of-the-art PET systems. To increase the overall detection efficiency for coincidence imaging, thick NaI(Tl) crystals are being used in these multi-purpose systems. Unfortunately, thick crystals enhance parallax errors that degrade reconstructed image resolution when the dual-Anger camera system is operated in coincidence-imaging mode; thick crystals also degrade intrinsic spatial resolution performance, particularly when imaging low- energy single-photon tracers. The effects of parallax errors can be minimized if the depth of interaction (DOI) of detected gamma rays is measured. In addition we believe the same DOI information could be used to improve intrinsic spatial resolution. We propose to study the feasibility of a method to use wavelength-shifting (WLS) scintillating optical fibers, coupled in a linear array to the entrance face of a large-area NaI(Tl) crystal, to measure DOI in Anger cameras. We hypothesize that the light output distribution measured by the scintillation fibers varies with DOI: the width of the distribution broadens as the site of interaction moves farther from the entrance face. In this research, we will develop the hardware and software necessary for performing DOI measurement with WLS scintillating fibers, particularly for thick large- area NaI(Tl) crystals like those used in commercial multi-purpose dual- head Anger camera systems. We will evaluate the ability of our approach to reduce parallax errors in coincidence imaging. We also will investigate the potential use of the derived DOI information in 3-D linearity correction techniques to the improve planar intrinsic spatial resolution of Anger cameras.