Comparison of different motion estimation methods for vessel cross-sectional shear wave imaging

In most studies on vascular shear wave imaging (SWI), longitudinal section is mainly concerned, and the radial motion and reflected waves are not considered in cross section. It is important to investigate the SWI in cross section when evaluating the anisotropy of the vessel wall or the complete plaque composition. In our previous study, a novel method based on coordinate transformation and directional filtering was proposed to achieve vessel cross-sectional shear wave imaging (VCS-SWI), where the radial motion was directly estimated in the polar coordinates of the vessel (referred to as the proposed method). The radial motion can also be calculated from the axial and lateral motions estimated in the Cartesian coordinate system of the transducer (referred as to Method 1), or from multiple axial motions with spatial angular compounding (referred as to Method 2). In this study, a comparison of the three methods for VCS-SWI was performed in simulations. The root-mean-square errors (RMSEs) of the estimated radial motions showed that the performance of radial motion estimation by using Method 1 is the worst due to the poor lateral motion estimation. With angular compounding, the radial motion can be well obtained, but at the cost of lower frame rate. The performance of the proposed method is similar to that of spatial angular compounding. In conclusion, the proposed method could obtain high-quality VCS-SWI without sacrificing the frame rate.