IEEE Trans Med Imaging. 2013 Oct;32(10):1829-39. doi: 10.1109/TMI.2013.2265886. Epub 2013 Jun 3.
We investigate an approach to evaluation of emission-tomography (ET) imaging systems used for region-of-interest (ROI) estimation tasks. In the evaluation we employ the concept of "emission counts" (EC), which are the number of events per voxel emitted during a scan. We use the reduction in posterior variance of ROI EC, compared to the prior ROI EC variance, as the metric of primary interest, which we call the "posterior variance reduction index" (PVRI). Systems that achieve a higher PVRI are considered superior to systems with lower PVRI. The approach is independent of the reconstruction method and is applicable to all photon-limited data types including list-mode data. We analyzed this approach using a model of 2-D tomography, and compared our results to the classical theory of tomographic sampling. We found that performance evaluations using the PVRI index were consistent with the classical theory. System evaluation based on EC posterior variance is an intuitively appealing and physically meaningful method that is useful for evaluation of system performance in ROI quantitation tasks.
我们研究了一种用于感兴趣区域（ROI）估计任务的发射断层成像（ET）成像系统的评估方法。在评估中，我们采用了“发射计数”（EC）的概念，即扫描期间每个体素发射的事件数。我们使用 ROI EC 的后验方差相对于 ROI EC 先验方差的减少来作为主要感兴趣的指标，我们称之为“后验方差减少指数”（PVRI）。具有更高 PVRI 的系统被认为优于具有更低 PVRI 的系统。该方法独立于重建方法，适用于所有光子受限的数据类型，包括列表模式数据。我们使用二维断层成像模型分析了这种方法，并将结果与断层成像采样的经典理论进行了比较。我们发现，使用 PVRI 指数进行的性能评估与经典理论一致。基于 EC 后验方差的系统评估是一种直观且有意义的方法，对于评估 ROI 定量任务中的系统性能非常有用。
