Tanaka E, Hasegawa T, Yamashita T, Okada H, Murayama H
Hamamatsu Photonics K.K., Tokyo Branch, Japan.
Phys Med Biol. 2000 Oct;45(10):2821-41. doi: 10.1088/0031-9155/45/10/307.
This paper presents a PET scanner capable of acquiring projection data in three-dimensional (3D) and two-dimensional (2D) modes simultaneously. The scanner has rotating partial slice-septa, and coincidence events are stored as 2D data or as 3D data depending on whether the lines of response are collimated by the septa or not. 68Ge/Ga rod sources can be set on the rotating septa, and a transmission scan for attenuation correction is performed in the 2D mode. The scanner allows simultaneous 3D-emission/2D-transmission scanning or post-injection transmission scanning with little cross-talk. A blank scan for detector normalization is also performed with the rotating rod sources in the 2D mode, from which we can derive the normalizing factors in both modes. The 3D/2D difference method is available for scatter correction, even in a dynamic study where the source distribution is changing. A 'summation method' is proposed as a new image reconstruction algorithm, in which the high- and low-frequency components of images are reconstructed from the 3D and 2D data respectively. In this method, most of the scatter contribution in the 3D data is removed by high-pass filtering, not by subtracting estimated scatter distribution, and hence the method is expected to be robust for scatter from outside the axial field of view. Computer simulations revealed that the rotating partial septa offer a single-scatter to true ratio similar to that of the conventional full septa if the depth of the partial septa is properly lengthened, with a small increase in multiple scattering.
本文介绍了一种能够同时以三维（3D）和二维（2D）模式采集投影数据的正电子发射断层扫描仪（PET）。该扫描仪具有旋转的部分切片隔板，符合事件根据响应线是否被隔板准直而存储为2D数据或3D数据。68Ge/Ga棒状源可设置在旋转隔板上，并在2D模式下进行用于衰减校正的透射扫描。该扫描仪允许进行几乎没有串扰的同时3D发射/2D透射扫描或注射后透射扫描。还使用旋转棒状源在2D模式下进行用于探测器归一化的空白扫描，从中我们可以得出两种模式下的归一化因子。即使在源分布不断变化的动态研究中，3D/2D差异法也可用于散射校正。提出了一种“求和法”作为一种新的图像重建算法，其中分别从3D和2D数据重建图像的高频和低频分量。在这种方法中，3D数据中的大部分散射贡献通过高通滤波去除，而不是通过减去估计的散射分布，因此该方法预计对轴向视野外的散射具有鲁棒性。计算机模拟表明，如果部分隔板的深度适当延长，旋转部分隔板提供的单散射与真计数比与传统的全隔板相似，多重散射略有增加。
