Biomedical Engineering Department, Huazhong University of Science and Technology, Wuhan, Hubei, China ; Wuhan National Laboratory for Optoelectronics, Wuhan, Hubei, China.
PLoS One. 2013 Aug 20;8(8):e72109. doi: 10.1371/journal.pone.0072109. eCollection 2013.
Positron emission tomography (PET) is an important imaging modality for clincial use. Conventionally, the PET scanner is generally built to provide a roomy enough transverse field-of-view (FOV) for imaging most adults' torsos. However, in many cases, the region-of-interest (ROI) for imaging is usually a small area inside the human body. Therefore, to fulfill a PET system which provides an FOV comparable in size to the target ROI seems appealing and more cost effective. Meanwhile, such a PET system has the potential for portable or bedside application with the reduced system size. In this work, we have investigated the feasibility of using dual-headed panel-detectors to build an ROI-focused PET scanner. A novel windowed list-mode ordered subset expectation maximization method was developed to perform the ROI image reconstruction. With this method, the ROI of the object can be reconstructed from the coincidences whose position determined by time-of-flight (TOF) measurements was inside the ROI. Monte Carlo simulation demonstrates the feasibility of detecting lesions not less than 1 cm in diameter, with a 300 ps full width at half maximum timing resolution. As a critical system performance, the impact of TOF information on image quality has been studied and the required TOF capability was assessed. With enhanced timing resolution, the distortions and artifacts were reduced effectively. The further improved TOF capability also shows a noticeable improvement of detection performance for low uptake lesions, as well as the recovery speed of lesion contrast, which is of practical significance in the lesion detection task.
正电子发射断层扫描（PET）是一种重要的临床成像方式。传统上，PET 扫描仪通常被构建为提供足够宽敞的横向视野（FOV），以对大多数成年人的躯干进行成像。然而，在许多情况下，成像的感兴趣区域（ROI）通常是人体内部的一个小区域。因此，为了满足提供与目标 ROI 大小相当的 FOV 的 PET 系统似乎很有吸引力，并且更具成本效益。同时，这种 PET 系统具有减小系统尺寸后实现便携式或床边应用的潜力。在这项工作中，我们研究了使用双头面板探测器构建 ROI 聚焦 PET 扫描仪的可行性。开发了一种新颖的带窗列表模式有序子集期望最大化方法来进行 ROI 图像重建。使用这种方法，可以根据时间飞行（TOF）测量确定的位置在 ROI 内的符合事件来重建物体的 ROI。蒙特卡罗模拟证明了检测直径不小于 1 厘米的病灶的可行性，具有 300ps 的全宽半最大值定时分辨率。作为关键的系统性能，研究了 TOF 信息对图像质量的影响，并评估了所需的 TOF 能力。随着定时分辨率的提高，有效减少了失真和伪影。进一步提高的 TOF 能力还显示出对低摄取病灶的检测性能的显著改善，以及病灶对比度的恢复速度，这在病灶检测任务中具有实际意义。
