Potential and limitations of angle-independent flow detection algorithms using radio-frequency and detected echo signals.

New techniques to estimate local blood and tissue velocities have been developed by several groups, including our own. The performance of these techniques is ultimately limited by the characteristics of ultrasonic imaging systems that determine the second-order statistics of speckle. These statistical parameters vary widely depending on the dimension of analysis in the image plane (lateral or axial) and on the echo input signal (radio-frequency or detected data). We use experiments and theory to examine these factors and describe their impact on the performance of our correlation-based technique for angle-independent tracking of blood or tissue motion. The results indicate that the second-order statistics determine the performance of our correlation-based algorithm and can be used to predict the performance of other angle-independent flow detection techniques.