embodiment tissue displacements are measured by tracking the motion in the rf data acquired from one time instance with respect to another rf data from a previous time instance in one aspect of this embodiment the displacements are measured between every two rf data acquired consecutively in time from the same location in the tissue tissue displacements that are obtained with this method are herein called relative tissue displacements in another aspect of this embodiment the displacements are measured with respect to a reference rf data frame which remains unchanged until several tissue displacements are measured tissue displacements that are obtained with this method are herein called absolute tissue displacements what is herein meant by tissue displacements can be but not limited to relative tissue displacements or absolute tissue displacements what is herein meant by one pair of consecutive measurements at one location is the displacement at the specified location which is measured at two consecutive time instances also consecutive measurement hereby means the same as one pair of consecutive measurements what is herein meant by region of interest is a region within the imaging window in which the tissue displacements are measured tissue displacements can be measured for a plurality of locations within the imaging window this plurality of locations constitutes the region of interest furthermore what is herein meant by one of said plurality of locations is one.