Konofagou E E, Ophir J
Department of Radiology, The University of Texas Medical School, Houston 77030, USA.
Phys Med Biol. 2000 Jun;45(6):1553-63. doi: 10.1088/0031-9155/45/6/311.
In elastography we have previously developed a tracking and correction method that estimates the axial and lateral strain components along and perpendicular to the compressor/scanning axis following an externally applied compression. However, the resulting motion is a three-dimensional problem. Therefore, in order to fully describe this motion we need to consider a 3D model and estimate all three principal strain components, i.e. axial, lateral and elevational (out-of-plane), for a full 3D tensor description. Since motion is coupled in all three dimensions, the three motion components have to be decoupled prior to their estimation. In this paper, we describe a method that estimates and corrects motion in three dimensions, which is an extension of the 2D motion tracking and correction method discussed before. In a similar way as in the 2D motion estimation, and by assuming that ultrasonic frames are available in more than one parallel elevational plane, we used methods of interpolation and cross-correlation between elevationally displaced RF echo segments to estimate the elevational displacement and strain. In addition, the axial, lateral and elevational displacements were used to estimate all three shear strain components that, together with the normal strain estimates, fully describe the full 3D normal strain tensor resulting from the uniform compression. Results of this method from three-dimensional finite-element simulations are shown.
在弹性成像中，我们之前开发了一种跟踪和校正方法，该方法可在外部施加压缩后，估计沿压缩机/扫描轴及其垂直方向的轴向和横向应变分量。然而，由此产生的运动是一个三维问题。因此，为了全面描述这种运动，我们需要考虑一个三维模型，并估计所有三个主应变分量，即轴向、横向和仰角（平面外）分量，以获得完整的三维张量描述。由于运动在所有三个维度上都是耦合的，因此在估计之前必须将三个运动分量解耦。在本文中，我们描述了一种估计和校正三维运动的方法，它是之前讨论的二维运动跟踪和校正方法的扩展。与二维运动估计类似，通过假设在多个平行仰角平面上可获得超声帧，我们使用了仰角位移射频回波段之间的插值和互相关方法来估计仰角位移和应变。此外，轴向、横向和仰角位移用于估计所有三个剪切应变分量，这些分量与法向应变估计一起，充分描述了由均匀压缩产生的完整三维法向应变张量。展示了该方法在三维有限元模拟中的结果。
