Behar Vera, Adam Dan, Lysyansky Peter, Friedman Zvi
Department of Biomedical Engineering, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
Ultrasonics. 2004 Mar;41(9):743-53. doi: 10.1016/j.ultras.2003.09.003.
In cardiac elastography, the regional strain and strain rate imaging is based on displacement estimation of tissue sections within the heart muscle carried out with various block-matching techniques (cross-correlation, sum of absolute differences, sum of squared differences, etc.). The accuracy of these techniques depends on a combination of ultrasonic imaging parameters such as ultrasonic frequency of interrogation, signal-to-noise ratio, size of a kernel used in a block-matching algorithm, type of data and speckle decorrelation. In this paper, we discuss the possibility to enhance the accuracy of the displacement estimation via nonlinear filtering of B-mode images before block-matching operation. The combined effect of a filter algorithm and a kernel size on the accuracy of the displacement estimation is analyzed using a 36-frame sequence of grayscale B-mode images of a human heart acquired by an ultrasound system operating at 1.77 MHz. It is shown that the nonlinear filtering of images enables to obtain the desired accuracy (less than one pixel) of the displacement estimation with smaller kernels than without filtering. These results are obtained for two filters--an adaptive anisotropic diffusion filter and a nonlinear Gaussian filter chain.
在心脏弹性成像中，区域应变和应变率成像基于使用各种块匹配技术（互相关、绝对差之和、平方差之和等）对心肌内组织切片进行的位移估计。这些技术的准确性取决于超声成像参数的组合，如询问超声频率、信噪比、块匹配算法中使用的内核大小、数据类型和散斑去相关。在本文中，我们讨论了在块匹配操作之前通过对B模式图像进行非线性滤波来提高位移估计准确性的可能性。使用由工作在1.77MHz的超声系统采集的人类心脏的36帧灰度B模式图像序列，分析了滤波算法和内核大小对位移估计准确性的综合影响。结果表明，与不进行滤波相比，图像的非线性滤波能够使用更小的内核获得所需的位移估计精度（小于一个像素）。这些结果是针对两种滤波器——自适应各向异性扩散滤波器和非线性高斯滤波器链获得的。
