Dept. of Electr. & Comput. Eng., Calgary Univ., Alta.
IEEE Trans Med Imaging. 1994;13(1):102-9. doi: 10.1109/42.276148.
The discrete filtered backprojection (DFBP) algorithm used for the reconstruction of single photon emission computed tomography (SPECT) images affects image quality because of the operations of filtering and discretization. The discretization of the filtered backprojection process can cause the modulation transfer function (MTF) of the SPECT imaging system to be anisotropic and nonstationary, especially near the edges of the camera's field of view. The use of shift-invariant restoration techniques fails to restore large images because these techniques do not account for such variations in the MTF. This study presents the application of a two-dimensional (2D) shift-variant Kalman filter for post-reconstruction restoration of SPECT slices. This filter was applied to SPECT images of a hollow cylinder phantom; a resolution phantom; and a large, truncated cone phantom containing two types of cold spots, a sphere, and a triangular prism. The images were acquired on an ADAC GENESYS camera. A comparison was performed between results obtained by the Kalman filter and those obtained by shift-invariant filters. Quantitative analysis of the restored images performed through measurement of root mean squared errors shows a considerable reduction in error of Kalman-filtered images over images restored using shift-invariant methods.
离散滤波反投影（DFBP）算法用于重建单光子发射计算机断层扫描（SPECT）图像，由于滤波和离散化的操作，会影响图像质量。滤波反投影过程的离散化会导致 SPECT 成像系统的调制传递函数（MTF）具有各向异性和非平稳性，特别是在相机视场的边缘附近。使用平移不变恢复技术无法恢复大图像，因为这些技术没有考虑到 MTF 的这种变化。本研究提出了一种二维（2D）平移变分卡尔曼滤波器，用于 SPECT 切片的后重建恢复。该滤波器应用于空心圆柱体、分辨率体模和包含两种冷点（球体和三棱柱）的大型截断圆锥体的 SPECT 图像。图像是在 ADAC GENESYS 相机上采集的。通过对卡尔曼滤波器和平移不变滤波器的结果进行比较，对恢复后的图像进行了定量分析，通过均方根误差的测量，表明卡尔曼滤波图像的误差明显小于平移不变方法恢复的图像的误差。
