Dept. of Electr. Eng. and Comput. Sci., Michigan Univ., Ann Arbor, MI.
IEEE Trans Image Process. 1995;4(2):147-61. doi: 10.1109/83.342189.
The paper presents a multidimensional nonlinear edge-preserving filter for restoration and enhancement of magnetic resonance images (MRI). The filter uses both interframe (parametric or temporal) and intraframe (spatial) information to filter the additive noise from an MRI scene sequence. It combines the approximate maximum likelihood (equivalently, least squares) estimate of the interframe pixels, using MRI signal models, with a trimmed spatial smoothing algorithm, using a Euclidean distance discriminator to preserve partial volume and edge information. (Partial volume information is generated from voxels containing a mixture of different tissues.) Since the filter's structure is parallel, its implementation on a parallel processing computer is straightforward. Details of the filter implementation for a sequence of four multiple spin-echo images is explained, and the effects of filter parameters (neighborhood size and threshold value) on the computation time and performance of the filter is discussed. The filter is applied to MRI simulation and brain studies, serving as a preprocessing procedure for the eigenimage filter. (The eigenimage filter generates a composite image in which a feature of interest is segmented from the surrounding interfering features.) It outperforms conventional pre and post-processing filters, including spatial smoothing, low-pass filtering with a Gaussian kernel, median filtering, and combined vector median with average filtering.
本文提出了一种用于磁共振图像（MRI）恢复和增强的多维非线性边缘保持滤波器。该滤波器利用帧间（参数或时间）和帧内（空间）信息来过滤 MRI 场景序列中的附加噪声。它将使用 MRI 信号模型的帧间像素的近似最大似然（等效于最小二乘）估计与修剪的空间平滑算法相结合，使用欧几里得距离判别器来保留部分体积和边缘信息。（部分体积信息是由包含不同组织混合物的体素生成的。）由于滤波器的结构是并行的，因此在并行处理计算机上实现它非常简单。解释了用于四组多自旋回波图像序列的滤波器实现的细节，并讨论了滤波器参数（邻域大小和阈值）对滤波器的计算时间和性能的影响。该滤波器应用于 MRI 模拟和大脑研究，作为特征图像滤波器的预处理步骤。（特征图像滤波器生成一幅复合图像，其中从周围干扰特征中分割出感兴趣的特征。）它优于传统的预处理和后处理滤波器，包括空间平滑、高斯核低通滤波、中值滤波和组合向量中值与平均滤波。
