Dept. of Radiol., Univ. of South Florida, Tampa, FL.
IEEE Trans Med Imaging. 1994;13(1):25-36. doi: 10.1109/42.276142.
A new class of nonlinear filters with more robust characteristics for noise suppression and detail preservation is proposed for processing digital mammographic images. The new algorithm consists of two major filtering blocks: (a) a multistage tree-structured filter for image enhancement that uses central weighted median filters as basic sub-filtering blocks and (b) a dispersion edge detector. The design of the algorithm also included the use of linear and curved windows to determine whether variable shape windowing could improve detail preservation. First, the noise-suppressing properties of the tree-structured filter were compared to single filters, namely the median and the central weighted median with conventional square and variable shape adaptive windows; simulated images were used for this purpose. Second, the edge detection properties of the tree-structured filter cascaded with the dispersion edge detector were compared to the performance of the dispersion edge detector alone, the Sobel operator, and the single median filter cascaded with the dispersion edge detector. Selected mammographic images with representative biopsy-proven malignancies were processed with all methods and the results were visually evaluated by an expert mammographer. In all applications, the proposed filter suggested better detail preservation, noise suppression, and edge detection than all other approaches and it may prove to be a useful tool for computer-assisted diagnosis in digital mammography.
为处理数字乳腺图像，我们提出了一种具有更强鲁棒性的新的非线性滤波器，用于抑制噪声和保留细节。新算法由两个主要的滤波块组成：（a）一个多阶段树状结构滤波器，用于图像增强，它使用中心加权中值滤波器作为基本子滤波块；（b）一个离散边缘检测器。算法的设计还包括使用线性和曲线窗口来确定可变形状窗口是否可以改善细节保留。首先，将树状滤波器的噪声抑制特性与单个滤波器（即中值和中心加权中值）进行比较，这些滤波器使用传统的正方形和可变形状自适应窗口；为此目的使用了模拟图像。其次，将与离散边缘检测器级联的树状滤波器的边缘检测特性与离散边缘检测器本身、Sobel 算子和与离散边缘检测器级联的单个中值滤波器的性能进行比较。使用所有方法对具有代表性活检证实的恶性肿瘤的选定乳腺图像进行处理，并由一位专家乳腺成像医生进行视觉评估。在所有应用中，与所有其他方法相比，所提出的滤波器在细节保留、噪声抑制和边缘检测方面表现更好，它可能成为数字乳腺计算机辅助诊断的有用工具。
