Woods R P, Cherry S R, Mazziotta J C
Department of Radiology, University of California, Los Angeles School of Medicine 90024-1721.
J Comput Assist Tomogr. 1992 Jul-Aug;16(4):620-33. doi: 10.1097/00004728-199207000-00024.
A computer algorithm for the three-dimensional (3D) alignment of PET images is described. To align two images, the algorithm calculates the ratio of one image to the other on a voxel-by-voxel basis and then iteratively moves the images relative to one another to minimize the variance of this ratio across voxels. Since the method relies on anatomic information in the images rather than on external fiducial markers, it can be applied retrospectively. Validation studies using a 3D brain phantom show that the algorithm aligns images acquired at a wide variety of positions with maximum positional errors that are usually less than the width of a voxel (1.745 mm). Simulated cortical activation sites do not interfere with alignment. Global errors in quantitation from realignment are less than 2%. Regional errors due to partial volume effects are largest when the gantry is rotated by large angles or when the bed is translated axially by one-half the interplane distance. To minimize such partial volume effects, the algorithm can be used prospectively, during acquisition, to reposition the scanner gantry and bed to match an earlier study. Computation requires 3-6 min on a Sun SPARCstation 2.
本文描述了一种用于正电子发射断层扫描（PET）图像三维（3D）对齐的计算机算法。为了对齐两幅图像，该算法逐体素计算一幅图像与另一幅图像的比率，然后迭代地相对移动图像，以使该比率在体素间的方差最小化。由于该方法依赖于图像中的解剖信息而非外部基准标记，因此可以进行回顾性应用。使用三维脑模型的验证研究表明，该算法能够对齐在各种位置获取的图像，最大位置误差通常小于一个体素的宽度（1.745毫米）。模拟的皮质激活位点不会干扰对齐。重新对齐导致的定量全局误差小于2%。当机架旋转大角度或床沿轴向平移平面间距的一半时，由于部分容积效应引起的区域误差最大。为了最小化这种部分容积效应，该算法可以在采集过程中前瞻性地用于重新定位扫描仪机架和床，以匹配早期的研究。在Sun SPARCstation 2上进行计算需要3 - 6分钟。
