Hsu Ching-Han, Huang Po-Chia
Department of Nuclear Science, National Tsing-Hua University, 101, Section 2, Kuang Fu Road, Hsinchu 300, Taiwan, ROC.
Comput Med Imaging Graph. 2006 Apr;30(3):181-5. doi: 10.1016/j.compmedimag.2006.03.004. Epub 2006 May 24.
Accurate system modeling of the photon acquisition process is essential for optimizing quality in pinhole SPECT imaging. Conventional pinhole SPECT imaging assumes ideal pinhole geometry. However, neglect of pinhole finite aperture could lead to unfavorable quality degradations, such as positioning bias and image distortion. In this work, we develop a system model in which the aperture width of a pinhole collimator is explicitly included. The system model describes the probability of a single photon from its emission to detection. The probability value is calculated based on the effective intersection area resulting from a simulated cone-beam light source emitting from the image voxel, passing through a finite aperture, and reaching the detector's frontal face. The proposed model can be integrated with the ordered subsets expectation maximization (OSEM) algorithm for fast 3D statistical image reconstruction. Monte Carlo-based phantom experiments are used to evaluate the performance of the proposed system model compared to the ideal pinhole model. Reconstructed image results demonstrate that the proposed model can improve image quality in terms of reducing location bias and maintaining better contrast recovery.
准确的光子采集过程系统建模对于优化针孔单光子发射计算机断层扫描（SPECT）成像质量至关重要。传统的针孔SPECT成像假定针孔几何形状理想。然而，忽略针孔有限孔径可能会导致不利的质量下降，如定位偏差和图像失真。在这项工作中，我们开发了一个系统模型，其中明确包含了针孔准直器的孔径宽度。该系统模型描述了单个光子从发射到检测的概率。概率值是基于从图像体素发射、穿过有限孔径并到达探测器正面的模拟锥束光源产生的有效相交面积计算得出的。所提出的模型可以与有序子集期望最大化（OSEM）算法集成，用于快速三维统计图像重建。基于蒙特卡罗的体模实验用于评估所提出的系统模型与理想针孔模型相比的性能。重建图像结果表明，所提出的模型在减少位置偏差和保持更好的对比度恢复方面可以提高图像质量。
