Wang G, Frei T, Vannier M W
Department of Radiology, University of Iowa, Iowa City 52242, USA.
Acad Radiol. 2000 Aug;7(8):607-14. doi: 10.1016/s1076-6332(00)80576-0.
The reduction of metal artifacts in x-ray computed tomography (CT) has important clinical applications. An iterative method adapted from the expectation maximization (EM) formula for emission CT was shown to be effective for metal artifact reduction, but its computational speed is slow. The goal of this project was to accelerate that iterative method for metal artifact reduction.
Using the row-action/ordered-subset (EM) formula for emission CT as a basis, the authors developed a fast iterative algorithm for metal artifact reduction. In each iteration of this algorithm, both reprojection from an intermediate image and backprojection from discrepancy data are performed.
The feasibility of the fast iterative algorithm was demonstrated in numerical and phantom experiments. In comparison with the nonaccelerated iterative algorithm, the speed of iterative metal artifact reduction is improved by an order of magnitude given image quality in terms of visual inspection, I-divergence in the projection domain, and the euclidean distance in the image domain.
The fast iterative algorithm corrects intermediate reconstruction according to subsets of projections and produces satisfactory image quality at a much faster speed than the previously published iterative algorithm. This algorithm has important potential in clinical applications, such as orthopedic, oncologic, and dental imaging.
降低X射线计算机断层扫描（CT）中的金属伪影具有重要的临床应用价值。一种源自发射型CT的期望最大化（EM）公式的迭代方法已被证明对减少金属伪影有效，但其计算速度较慢。本项目的目标是加速这种减少金属伪影的迭代方法。
以发射型CT中的行作用/有序子集（EM）公式为基础，作者开发了一种用于减少金属伪影的快速迭代算法。在该算法的每次迭代中，都会进行从中间图像的重投影和从差异数据的反投影。
数值实验和体模实验证明了快速迭代算法的可行性。与未加速的迭代算法相比，在视觉检查的图像质量、投影域中的I散度以及图像域中的欧几里得距离方面，迭代减少金属伪影的速度提高了一个数量级。
快速迭代算法根据投影子集校正中间重建，并以比先前发表的迭代算法快得多的速度产生令人满意的图像质量。该算法在骨科、肿瘤学和牙科成像等临床应用中具有重要潜力。
