Improvement of elastographic displacement estimation using a two-step cross-correlation method
Improvement of elastographic displacement estimation using a two-step cross-correlation method
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DOI：
10.1016/j.ultrasmedbio.2006.07.022
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发表时间：
2007-01-01
影响因子：
2.9
通讯作者：
Varghese, Tomy
中科院分区：
文献类型：
--
作者：
Chen, Hao;Shi, Hairong;Varghese, Tomy
用于计算弹性成像局部应变分量的互相关算法需要大约10个波长的最小射频数据段长度，才能在合理的信噪比下获得准确和精确的应变估计。随着数据段中信息量的减少，较短的射频数据段通常会带来更大的估计误差。然而，为了提高应变图像的轴向分辨率，需要更短的数据段和更多的重叠。在本文中，我们提出了一种两步互相关技术，该技术能够使用单个波长量级的窗口长度来提供具有类似于10个波长窗口所获得的噪声特性的位移和应变估计。第一处理步骤利用10个波长数量级的窗口长度来获得压缩前和压缩后射频数据之间的粗略位移估计，然后对其进行内插，并使用较小的窗口作为第二互相关处理步骤的初始猜测估计。这一步骤利用单个波长窗口来提高应变估计中的轴向分辨率，而不会显著影响图像的噪声特性。仿真和实验结果表明，与当前使用的单窗口方法中使用类似大小的窗口相比，两步处理在较小窗口长度下的信噪比和对比噪声比估计有显著改善。(电子邮件：tvarghese@witc.edu)(C)2006年世界医学和生物学超声联合会。
The cross-correlation algorithm used to compute the local strain components for elastographic imaging requires a minimum radio-frequency data segment length of around 10 wavelengths to obtain accurate and precise strain estimates with a reasonable signal-to-noise ratio. Shorter radio-frequency data segments generally introduce increased estimation errors as the information content in the data segment reduces. However, shorter data segments and increased overlaps are essential to improve the axial resolution in the strain image. In this paper, we propose a two-step cross-correlation technique that enables the use of window lengths on the order of a single wavelength to provide displacement and strain estimates with similar noise properties as those obtained with a 10 wavelength window. The first processing step utilizes a window length on the order of 10 wavelengths to obtain coarse displacement estimates between the pre- and postcompression radio frequency data is then interpolated and utilized as the initial guess-estimate for the second cross-correlation processing step using the smaller window. This step utilizes a single wavelength window to improve the axial resolution in strain estimation, without significantly compromising the noise properties of the image. Simulation and experimental results show that the signal-to-noise and contrast-to-noise ratio estimates improve significantly at the smaller window lengths with the two-step processing when compared with the use of a similar sized window in the currently utilized single window method. (E-mail: tvarghese@wisc.edu) (c) 2006 World Federation for Ultrasound in Medicine & Biology.