“…For methods in the latter category, a set of features are used to measure the variations between adjacent images: crosscorrelation [5], [9], [10], [12], sum of squared distances (SSD) [14], local mean variation [4], [11], [12], [15], Gabor filters' descriptors [8] or radial blurring [13]. It is worth noting that the blurring feature measures the motion by perturbations over the transducer probe being not sensitive to topological variations, while features like cross-correlation or SSD measure by differences between adjacent frames.…”