Du Y P, Parker D L, Davis W L
Department of Radiology, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA.
J Magn Reson Imaging. 1995 Mar-Apr;5(2):151-7. doi: 10.1002/jmri.1880050207.
For a variety of reasons, small vessels have low signal intensity in magnetic resonance angiography. When the vessel signal intensity is lower than the signal intensity of background tissues, these vessels tend not to be visible on maximum-intensity-projection images. The authors developed a nonlinear second-difference spatial filtering technique that enhances the details of small vessels while suppressing both noise and uniform background tissue. Two similar nonlinear second-difference filters are presented and compared with the linear Laplacian second-difference filter. To evaluate the performance of these filters, they were applied to intracranial three-dimensional time-of-flight MR angiographic data and the results compared with the vessel enhancement obtained with a simple second-difference Laplacian filter and with magnetization transfer contrast (MTC) techniques. The comparisons demonstrated that nonlinear filtering and MTC techniques result in similar improvement in small-vessel visibility and apparent continuity. A quantitative comparison demonstrated that the improvement in the contrast-to-noise ratio is much greater with the nonlinear filters than the Laplacian filter.
由于多种原因，小血管在磁共振血管造影中信号强度较低。当血管信号强度低于背景组织的信号强度时，这些血管在最大强度投影图像上往往不可见。作者开发了一种非线性二阶差分空间滤波技术，该技术在抑制噪声和均匀背景组织的同时增强了小血管的细节。提出了两种类似的非线性二阶差分滤波器，并与线性拉普拉斯二阶差分滤波器进行了比较。为了评估这些滤波器的性能，将它们应用于颅内三维时间飞跃磁共振血管造影数据，并将结果与使用简单二阶差分拉普拉斯滤波器和磁化传递对比（MTC）技术获得的血管增强效果进行比较。比较表明，非线性滤波和MTC技术在小血管可见性和表观连续性方面的改善相似。定量比较表明，非线性滤波器在对比度噪声比方面的改善比拉普拉斯滤波器大得多。
