Ultrasound low-velocity flow estimations using cross-correlation and decorrelation: a thread phantom study.

In this paper, two time-domain flow velocity measurement methods, cross-correlation and decorrelation, were implemented and compared in measuring low blood-flow velocities, ranging from 0.05 to 5 cm/s, at known beam-vessel angles of 50-90 degrees in a thread phantom. Both methods achieved a significant correlation between the measured and the known velocities (r=0.99; P<0.001) in the thread phantom measurements, at 50-70 degrees beam-vessel angles. Although the cross-correlation method showed a significant correlation (r>0.99; P<0.001), this method caused large errors (>45%) at 80 degrees and 90 degrees , whereas the decorrelation method not only achieved a significant correlation (r>0.99; P<0.001) but also resulted in smaller errors (<19%) at 80 degrees and 90 degrees . This study demonstrates the potential of time-domain decorrelation method for measuring low flow velocity at large beam-vessel angles near perpendicular conditions.