A method to reduce the influence of reflected waves on shear velocity measurements using B-mode scanning time delay

A method to reduce the influence of reflected shear wave (SW) on ultrasound measurement of shear velocity of a soft tissue specimen was proposed in this study. A backward SW reflected from tissue boundaries may interfere with a forward SW induced, resulting in shear velocity measurement error. In the B-mode scan of a conventional ultrasound imaging system there is a scanning time delay among the sequential A-mode measurements, which causes an artificial spatial frequency shift in the forward and backward SWs. The amount of the frequency shift is dependent on the propagation direction of the SWs with respect to the B-mode scanning direction. Therefore, the forward and backward SWs can be separated using a spatial frequency filter. The proposed method was verified using a soft tissue mimicking phantom. In the experimental results, the artificial frequency shifts were clearly observed for induced and reflected SW. Shear velocities of the phantoms were successfully measured from the filtered SW by the proposed method.