A fundamental limit on the accuracy of speckle signal alignment

Signal alignment is performed in phase aberration correction and measurement, tissue elasticity estimation, and tissue and blood velocity estimation. The performance of all these techniques is limited by errors in the alignment of signals received from speckle generating targets. We have derived an analytical expression based on the Cramer-Rao lower bound which predicts the magnitude of jitter errors resulting from the alignment of radio frequency speckle data. The expression includes the effects of finite length samples of data, signal decorrelation, electronic noise, signal bandwidth, and center frequency. This expression indicates that signal decorrelation is a significant source of jitter for many ultrasound applications