1. A method of ultrasound strain imaging comprising the steps of: (a) acquiring first and second ultrasound echo data with an axial ultrasonic beam passing through a material subject to a first and second state of axial deformation, respectively, the echo data corresponding to a plurality of volume elements identified by a plurality of columns extending substantially parallel to an axis of propagation of the beam and a plurality of rows extending substantially perpendicular to the axis of propagation of the beam; and (b) calculating a displacement vector for at least one of the plurality of volume elements to determine displacement of the material by comparing the first and second echo data on a column-by-column basis, wherein a determination of displacement vectors for the volume elements of a first column is substantially complete before a determination of displacement vectors for the volume elements of at least one second column to be determined is substantially begun; and (c) producing elasticity images of the material using determinations of displacement between the first and second ultrasound echo data.