Myocardial strain imaging based on three-dimensional motion tracking

The decrease of myocardial wall motion, caused by changes in wall stiffness, often appears 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. Therefore, we propose novel methods to track the 3-D motion using a 2-D phased array and to assess myocardial malfunction by visualizing the invariant of a full strain tensor. The feasibilities of the proposed methods were evaluated by numerically simulating short-axis imaging of a 3-D myocardial model. This model includes a hard infarction, located between 1 and 3 o'clock, which is difficult to detect by conventional tissue Doppler and strain-rate imaging. RF signals received at each element on a 2-D phased array 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 the conventional imaging could not.