Enhancing the performance of lateral shear strain estimation by using 2-D strain imaging

Radio-frequency (RF) ultrasound can be used to estimate deformation of biological tissue. Decorrelation of sequentially acquired ultrasound signals resulting from the deformation imposes a limitation on the precision (elastographic signal-to-noise ratio; SNRe) of estimating these deformations; this is presented as the lateral shear strain filter. In this paper, we explore the effect of a 2-D-window-based strain estimation approach on the lateral shear strain filter and propose an extension of the 1-D theoretical lateral shear strain filter to 2-D. We compared the performance of the 2-D approach in simulated ultrasound data and a tissue-mimicking phantom with that of the 2-D lateral shear strain filter. In simulations, the 2-D-window-based approach shows an effect in the axial direction similar to the 2-D prediction. In simulations and experiments, increasing the window size in the lateral direction shows an increase in the maximum SNRe of the lateral shear strain filter. Increasing the lateral overlap has no effect on the estimation of lateral shear strain. These results were confirmed in the tissue-mimicking phantom experiments. When compared with the 2-D lateral shear strain filter, the results obtained with the 2-D-window-based approach showed an enhanced performance by incorporating the lateral window size in the lateral shear strain estimation, which was consistent with the proposed theory.