Cai J, Chu J C, Saxena V A, Lanzl L H
Department of Medical Physics, Rush Presbyterian St. Luke's Medical Center, Rush University, Chicago, Illinois 60612, USA.
Med Phys. 1998 Jun;25(6):824-9. doi: 10.1118/1.598292.
A simple algorithm is presented for planar image registration and the method is applied to the simulator and portal image registration for patient setup verification in radiation therapy. Basically, the algorithm follows the concept proposed by Balter et al. [Med. Phys. 19, 329-334 (1992)], which converts the problem of open curve registration into matching a series of points along the curves. Balter's algorithm consists of three steps: (1) to determine a common starting point for each curve pair, (2) acquire two corresponding point sets along each curve, and (3) obtain a global transform matrix by matching two point sets. We integrate all three steps into one simple procedure which fits the sampled points along the intended curve pair by taking the relative path length shift as an independent fitting parameter. After being modified, the algorithm is able to take the different magnification factors of images into account, and it avoids curvature calculations. Numerical simulation as well as clinical and phantom images have been utilized to test the accuracy of the algorithm. The typical errors are less than 1 mm in translation and 1 degree in rotation. We also made a comparison study with the chamfer method. The results of the two methods agree to within 0.5 mm in translation and 0.5 degree in rotation.
本文提出了一种用于平面图像配准的简单算法，并将该方法应用于模拟器和射野图像配准，以在放射治疗中进行患者摆位验证。该算法基本上遵循了Balter等人[《医学物理》19, 329 - 334 (1992)]提出的概念，即将开放曲线配准问题转化为沿曲线匹配一系列点的问题。Balter的算法包括三个步骤：(1) 为每对曲线确定一个公共起点；(2) 沿每条曲线获取两个相应的点集；(3) 通过匹配两个点集获得全局变换矩阵。我们将这三个步骤整合为一个简单的过程，通过将相对路径长度偏移作为独立的拟合参数，对沿预期曲线对的采样点进行拟合。经过修改后，该算法能够考虑图像的不同放大倍数，并且避免了曲率计算。利用数值模拟以及临床和体模图像对该算法的准确性进行了测试。典型的平移误差小于1毫米，旋转误差小于1度。我们还与倒角法进行了比较研究。两种方法的结果在平移方面相差0.5毫米以内，在旋转方面相差0.5度以内。
