Techavipoo U, Chen Q, Varghese T, Zagzebski J A
Department of Medical Physics, The University of Wisconsin-Madison, Madison, WI 53706, USA.
IEEE Trans Med Imaging. 2004 Dec;23(12):1479-89. doi: 10.1109/TMI.2004.835604.
In current practice, only one out of three components of the tissue displacement vector and one of nine components of the strain tensor are accurately estimated and imaged in ultrasound elastography. Since, only the axial component of both the displacement and strain are imaged, other important elastic parameters, such as shear strains and the Poisson's ratio, also are not imaged. Moreover, reconstruction of the Young's modulus would be significantly improved if all components of the strain tensor were available. In this paper, we describe a new method for estimating all the components of the tissue displacement vector following a quasi-static compression. The method uses displacements estimated from radiofrequency echo-signals along multiple ultrasound beam insonification directions. At each spatial location in the compressed medium, orthogonal tissue displacements in both the axial and lateral direction with respect to the direction of the applied compression are estimated by curve fitting angular displacement vector data calculated for all insonification directions. Following displacement estimation in orthogonal directions, components of the corresponding normal and shear strain tensors are estimated. Simulation and experimental results demonstrate the utility of this technique for the computation of the normal and shear strain tensors.
在当前的实践中，在超声弹性成像中，组织位移矢量的三个分量中只有一个以及应变张量的九个分量中的一个能够被准确估计并成像。由于仅对位移和应变的轴向分量进行成像，其他重要的弹性参数，如剪切应变和泊松比，也无法成像。此外，如果应变张量的所有分量都可用，杨氏模量的重建将得到显著改善。在本文中，我们描述了一种在准静态压缩后估计组织位移矢量所有分量的新方法。该方法使用从沿多个超声束声照射方向的射频回波信号估计的位移。在压缩介质中的每个空间位置，通过对为所有声照射方向计算的角位移矢量数据进行曲线拟合，估计相对于施加压缩方向的轴向和横向的正交组织位移。在正交方向上进行位移估计后，估计相应的法向和剪切应变张量的分量。模拟和实验结果证明了该技术在计算法向和剪切应变张量方面的实用性。
