DETERMINATION OF SCAN-PLANE MOTION USING SPECKLE DECORRELATION - THEORETICAL CONSIDERATIONS AND INITIAL TEST

The correlation function of the echo signal intensities at a fixed reg ion on a series of B-mode images is directly related to the change of speckle patterns between these images. An indication is given here of how the rate of the change of that correlation function can be used to estimate the scan-plane motion in any direction relative to the image d tissue or other material. In this first implementation it is assumed that the statistical properties of the echo signals follow those of a complex circular Gaussian, and the case is considered of diffusely sc attering tissue with many fine particles per resolution cell and with no phase distortion. The method is applied to data from a one-dimensio nal linear array and initial results are presented for scanning a tiss ue-mimicking phantom in the elevational direction of the transducer. E xperimental results are in good agreement with the predictions. The cu rrent method should provide a good indication of the local rate of sca n-head motion in those tissues in which the normalized correlation fun ction of the echo signal intensities behaves, or can be made to behave , as it would for a medium with uniform acoustic properties and contai ning many, randomly distributed, pointlike scatterers, although applic ation might be made to other situations where a deterministic conditio n exists for the correlation between images taken at differing locatio ns within a volume. (C) 1997 John Wiley & Sons, Inc.