Mapping HPGe double-sided strip detector with x-rays for improved detector performance and position estimation

 描述(申请人提供)：单光子发射计算机断层扫描(SPECT)是一种核医学成像技术，可以绘制注射的放射性示踪剂的生物分布图；根据放射性示踪剂的类型，可以研究一系列主题，如：精神和神经退行性疾病、各种类型的癌症、肺血栓和心脏病。我们目前正在建造一个双头SPECT系统，该系统使用双面条状高纯度锗(DSS HPGe)探测器。HPGe提供了比传统NaI伽马相机高一个数量级的能量分辨率(140keV时为1%)，其电荷传输特性使空间分辨率与CDZnTe像素探测器相似，同时使用的读出电子通道要少得多。DSS配置允许亚像素定位，然而，探测器内的电荷共享、电荷损失和康普顿散射等多重条带效应可能会导致事件定位错误和/或无法计数。这降低了检测效率和整体灵敏度，可能导致重建图像中出现伪影。替代的、先进的后处理技术已被证明可以在有限的情况下校正这些影响(特定的探测器配置和/或仅调查较小的探测器区域)。这项研究的目标是研究和实现以下后处理技术：波形分析，最大似然(ML)估计，以及整个探测器的电荷损失校正。这将通过三个目标来完成：目标1)使用阿贡国家实验室的先进光子源(APS)仔细测量探测器系统的响应；目标2)对目标1中获得的数据执行位置估计技术。有了这些数据集(每种技术一个)和光束位置的知识，可以使用最大似然估计来确定每个事件的三维位置(请注意，一种技术是尝试最大似然方法，而不需要额外的后处理)。每种技术都将通过测量：一致性、能量和空间分辨率，以及对投影图像的评估(空间分辨率、信噪比、调制传递函数等)进行评估，目标3)使用新的SPECT系统实施新的位置估计技术，并评估新重建图像与我们当前的后处理技术之间的差异。我们期望得到的重建SPECT图像具有更高的分辨率、灵敏度和对比度，以及更少的伪影，从而产生更好的可检测性。

 DESCRIPTION (provided by applicant): Single Photon Emission Computed Tomography (SPECT) is a nuclear medicine imaging technique that allows for the mapping of the biological distribution of an injected radiotracer; depending on the type of radiotracer a range of topics may be studied, such as: mental and neurodegenerative disorders, various types of cancers, pulmonary embolisms, and heart disease. We are currently building a dual-headed SPECT system that uses double-sided strip, high-purity germanium (DSS HPGe) detectors. HPGe offers an energy resolution (FWHM < 1% at 140 keV) an order of magnitude better than conventional NaI gamma cameras, and its charge transport properties enable spatial resolutions similar to that of CdZnTe pixel detectors while using far fewer channels of readout electronics. The DSS configuration allows for sub-pixel positioning, however, multiple strip effects such as charge sharing, charge loss and Compton scattering within the detector can cause the events to be mis- positioned and/or uncounted. This decreases detection efficiency and overall sensitivity, possibly leading to artifacts in the reconstructed image. Alternative, advanced post-processing techniques have been shown to correct for these effects in limited cases (specific detector configurations and/or only small detector areas investigated). The goal of this proposed study is to investigate and implement the following post-processing techniques: waveform analysis, Maximum-Likelihood (ML) estimation, and charge loss correction across the whole detector. This will be done in three aims: Aim 1) Carefully measure the detector system response using the Advanced Photon Source (APS) at Argonne National Laboratory, Aim 2) Perform the position estimation techniques on the data obtained in aim 1. With these data sets (one for each technique) and knowledge of the beam position the three-dimensional position of each event may be determined using the ML estimation (note that one technique is to try the ML method without additional post-processing). Each technique will be evaluated by measuring: uniformity, energy and spatial resolution, and evaluation of a projected image (spatial resolution, signal- and contrast-to-noise ratio, modulation transfer function, etc), and Aim 3) Implement the new position estimation technique with the new SPECT system and evaluate the differences between the new reconstructed image compared to our current post-processing technique. We expect to obtain reconstructed SPECT images that have higher resolution, sensitivity, and contrast, as well as fewer artifacts, leading to better detectability.