Arterial wall motion stiffening around a severe stenosis plaque. Figure 5 shows an example of arterial wall motion across a plaque with 70% stenosis (diameter reduction). High dilation gradients at the plaque vessel interface and localized stiffening with constricted wall motion at the plaque are demonstrated. See Additional file 4 for the real-time movie of the top right image. The lower right graph displays the dilation data as a surf plot with dilation plotted as a function of the spatial position and the time.