Initial results with the real-time SAD vector velocity estimation systems: constant velocity calibration

Doppler flow imaging systems are limited by angle-dependence and aliasing. A velocity estimator which uses the sum absolute difference (SAD) algorithm to track the motion of speckle in two dimensions between successive ultrasonic frames has been constructed. The system´s performance is evaluated in quantifying velocities of a string phantom moving at various angles relative to the transducer axis. The results show that the system is capable of tracking velocities well beyond the Doppler aliasing limit along any direction within the imaging plane