ENHANCEMENT OF ECHO-SIGNAL CORRELATION IN ELASTOGRAPHY USING TEMPORALSTRETCHING

Echo-signal decorrelation due to tissue compression is a significant s ource of error in tissue displacement estimates obtained using crossco rrelation. Tissue displacement estimates are used to compute strain va lues for imaging the elasticity of biological soft tissues. The correl ation coefficient between the pre- and post-compression echo rf signal s reduces rapidly with signal decorrelation due to increased compressi on. Miniscule reductions in the value of the correlation coefficient c an have a significant impact on the performance of the strain estimato r as illustrated by the strain filter. Reducing the rate of signal dec orrelation using temporal stretching (which improves the value of the correlation coefficient), significantly improves the performance of th e strain filter. The reduction in the rate of signal decorrelation wit h the subsequent increase in the correlation coefficient using tempora l stretching is discussed in this paper. Theoretical, simulation and e xperimental results quantify the enhancement in the value of the corre lation coefficient attained with temporal stretching.