The effect of nonlinear signal transformations on bias errors in elastography.

We have reported several artifacts in elastography (1991). These include mechanical artifacts, such as stress concentration, and signal processing artifacts, such as zebras, which are caused by bias errors incurred during the estimation of the peak of correlation functions using a curve-fitting method. We investigate the bias errors and show that bias errors in curve-fitting methods are substantially increased because of nonlinear operations on the echo signals that reduce other errors. We also show that, for typical sampling rates, the bias errors can be ignored in the absence of these nonlinear operations.