SPECKLE DECORRELATION DUE TO 2-DIMENSIONAL FLOW GRADIENTS

The performance of ultrasonic velocity estimation methods is degraded by speckle decorrelation, the change in received echoes over time. Bec ause ultrasonic speckle is formed by the complex sum of echoes from su bresolution scatterers, it is sensitive to the relative motion of thos e scatterers. Velocity gradients in flowing blood result in relative s catterer motion and can be a significant source of speckle decorrelati on. Computer simulations were performed to evaluate speckle decorrelat ion due to two-dimensional flow gradients. Results indicate that decor relation due to flow gradients is sensitive to the angle of flow and h as a maximum at a beam-vessel angle of 0 degrees, i.e., purely axial f low. A quantitative summary of the major factors causing speckle decor relation indicates that flow gradients are the most significant contri butors under the conditions modeled.