<title>Correlation-tracking strain estimator for elastography</title>

Abstract

We describe a novel strain estimation method, which is capable of accurate strain estimation in the presence of large or irregular tissue motion. In conventional elastography, tissue strains induced by external compression applied to the tissue surface, are estimated by cross-correlation analysis of echo signals obtained before and after compression. Large and irregular tissue motions significantly change echo-signal shapes, causing major echo-signal decorrelations. In the presence of significant signal decorrelations, the estimated displacements may have many discontinuities because of false peak errors (primary correlation peak smaller than a secondary peak). However, because tissue is virtually incompressible, true elastographic displacements have spatial continuity in both axial and lateral directions, and the true correlation peaks, albeit diminished, are still present and detectable in the presence of spurious peaks. Our approach treats the total ensemble of correlation functions vs. depth and use information from neighboring areas to remove ambiguity that results from false peak errors. Preliminary results using finite-element simulation show that the correlation-tracking strain estimator (CTSE) can produce excellent strain estimates in harsh environments.