FIG. 4.

In vivo two-dimensional ARFI imaging demonstration of the improvement of the quadratic motion filter by including pre-excitation displacement estimates. From a passive ARFI imaging acquisition, absolute residual displacement images (ìm away from the transducer), taken 0.66 ms after cessation of the zero-amplitude radiation force pulse, were formed at systole. (a) The B-mode image shows a section of left ventricular myocardium located near the apex. By motion filtering with displacement estimates taken only after the end-time threshold, (b) the residual displacement ARFI image contains considerable physiological motion artifacts, as an appreciable amount of the image is non-zero. By including pre-excitation displacement estimates in the quadratic motion filter, physiological motion artifacts are markedly reduced, as (c) the corresponding residual displacement ARFI image has become more uniform and closer to zero.