Optimization of the strain tensor estimation for cross sectional non-invasive elastography of the carotid using plane wave imaging

Full-2D strain tensor estimation using non-invasive vascular elastography (NIVE) can be difficult to achieve using conventional beamforming methods due to its low lateral resolution. Angular compounding can help improving estimates of lateral components. However, using conventional focused imaging, compounding decreases dramatically the frame rate thus increasing the probability of decorrelation artefacts. As it can reconstruct the full field of view (FOV), using a single unfocused emission, plane wave imaging (PWI) can reach very high frame rate without significant loss of signal-to-noise ratio (SNR). In this study, we investigated the performance of compounding elastography using the lagrangian speckle model estimator (LSME) on tilted plane wave images. We introduced two compounding methods based on oriented strain fields without any mechanical assumptions. We evaluate our methods on both simulation and in-vitro data. It was found that, as well as conventional focused imaging, PWI can provide high quality axial strain and shear and significantly better lateral strain and shear. Moreover, the combination of compound elastography with tilted PWI improved significantly the quality of elastograms.