Strain imaging using combined RF and envelope autocorrelation processing

Considering that large displacements are desired for elasticity imaging to improve the strain signal to noise ratio, we have developed a method for strain imaging that is both fast to calculate and applicable to the measurement of large displacements. The method has the merits of phase domain processing but without aliasing, since it combines the result of phase correlation with that of envelope correlation, both of which are calculated directly from the radio frequency (RF) signal using complex autocorrelation processing. Results from experiments using a computer simulation indicate that the method is capable of reliably estimating tissue displacement and strain over a large range of displacements beyond the Doppler aliasing limit with no prior knowledge of expected displacement.