Development of Real-Time Three-Dimensional Ultrasonic Myocardial Strain Imaging

缺血性心脏病的早期常出现组织硬度变化引起的心肌运动减少。由于心肌表现出复杂的三维运动，三维评估的刚度分布需要准确的诊断。然而，传统的组织多普勒和应变率成像技术不能完全满足上述要求，因为它们是角度相关的和平面内（2-D）处理，并且对于大的心肌运动存在混叠问题。我们提出了新的方法来跟踪3-D运动，通过使用2-小孔径三维相控阵，并根据三维运动分析获得的全应变张量评估心肌功能不全。作为一种新的三维心肌运动跟踪方法，我们结合了我们的相位梯度法，它能够实时三维位移矢量测量的基础上获得的相移在一个二维相控阵列上的每个元素，和我们的组合自相关法， ...更多信息 该方法可以精确测量每个元件的大相移，而不会产生混叠。作为一种新的方法来评估心肌组织刚度，全应变张量不变量的三维矢量测量得到的可视化作为一个应变不变量图像。由于应变张量不变量与坐标系、视轴和射束方向无关，因此可以独立于入射角评估有效的心肌刚度。该模型包括位于1点和3点之间的硬梗死，在该位置难以通过常规组织多普勒和应变率成像检测到。通过对模型中的点扩展函数和散射系数进行卷积，忠实地模拟了二维阵列探头上每个单元处接收到的射频信号。当模拟回波处理所提出的方法，由全应变张量得到的不变图像清晰地描绘了硬梗死区，常规成像不能。少

Decreases of myocardial motion caused by changes in tissue stiffness often appear in the early stage of ischemic heart disease. Since the myocardium exhibits complex 3-D motion, 3-D assessment of the stiffness distribution is required for accurate diagnosis. However, conventional tissue Doppler and strain-rate imaging techniques cannot meet the above requirement completely because they are angle-dependent and in-plane (2-D) processing, and have the aliasing issue for large myocardial motion.In order to overcome these problems, we propose novel methods to track the 3-D motion by using a 2-D phased array with a small aperture and to assess myocardial malfunction based on full strain tensors obtained by 3-D motion analysis. As a new method of 3-D myocardial motion tracking, we incorporated our phase-gradient method, which is capable of real-time 3-D displacement vector measurement based on the phase shifts obtained at each element on a 2-D phased array, and our combined autocorrelation me … More thod, which accurately measures large phase shifts at each element without aliasing. As a new method of assessing myocardial tissue stiffness, the full strain tensor invariant obtained by the measured 3-D vectors is visualized as a strain invariant image. Since strain tensor invariants are independent of the coordinate system, visual axis and beam direction, valid myocardial stiffness can be assessed independently of incident angle.We evaluated the feasibilities of the proposed methods by numerically simulating the left ventricle short-axis imaging of a 3-D elliptic myocardial model. This model includes a hard infarction, located between 1 and 3 o'clock, where it is difficult to detect by, conventional tissue Doppler and strain-rate imaging. RF signals received at each element on the 2-D array probe were faithfully simulated by convoluting the PSF and the scatter coefficients in the model. When the simulated echoes were processed by the proposed methods, the invariant image obtained by the full strain tensor clearly depicted the hard infarction area where conventional imaging could not. Less