1. A system, comprising: circuitry for processing two or more fiducials included in a three-dimensional medical image and included in a current image to generate two or more transform coefficients of a transform; and circuitry for applying the transform, the transform including at least stress and strain information obtained from observing how an elastic wave moves from one or more arteries into distal tissue in response to natural brain pulses, to the three-dimensional medical image to form a present image.