O'Connor M K, Vermeersch C
Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905.
Med Phys. 1991 Mar-Apr;18(2):190-7. doi: 10.1118/1.596706.
It is generally recognized that single-photon emission computed tomography (SPECT) imposes very stringent requirements on gamma camera uniformity to prevent the occurrence of ring artifacts. The purpose of this study was to examine the relationship between nonuniformities in the planar data and the magnitude of the consequential ring artifacts in the transaxial data, and how the perception of these artifacts is influenced by factors such as reconstruction matrix size, reconstruction filter, and image noise. The study indicates that the relationship between ring artifact magnitude and image noise is essentially independent of the acquisition or reconstruction matrix sizes, but is strongly dependent upon the type of smoothing filter applied during the reconstruction process. Furthermore, the degree to which a ring artifact can be perceived above image noise is dependent on the size and location of the nonuniformity in the planar data, with small nonuniformities (1-2 pixels wide) close to the center of rotation being less perceptible than those further out (8-20 pixels). Small defects or nonuniformities close to the center of rotation are thought to cause the greatest potential corruption to tomographic data. The study indicates that such may not be the case. Hence the uniformity requirements for SPECT may be less demanding than was previously thought.
人们普遍认识到，单光子发射计算机断层扫描（SPECT）对伽马相机的均匀性提出了非常严格的要求，以防止环形伪影的出现。本研究的目的是检查平面数据中的不均匀性与轴向数据中相应环形伪影的大小之间的关系，以及这些伪影的可察觉程度如何受到重建矩阵大小、重建滤波器和图像噪声等因素的影响。研究表明，环形伪影大小与图像噪声之间的关系基本上与采集或重建矩阵大小无关，但在很大程度上取决于重建过程中应用的平滑滤波器类型。此外，在图像噪声之上能够察觉到环形伪影的程度取决于平面数据中不均匀性的大小和位置，靠近旋转中心的小不均匀性（1 - 2像素宽）比远离旋转中心的不均匀性（8 - 20像素）更不易察觉。靠近旋转中心的小缺陷或不均匀性被认为对断层数据造成的潜在破坏最大。但研究表明情况可能并非如此。因此，SPECT的均匀性要求可能比之前认为的要低。
