  The accurate quantification of blood flow in aortoiliac arteries is
challenging but clinically relevant because local flow patterns can influence
atherosclerotic disease. To investigate the feasibility and clinical
application of two-dimensional blood flow quantification using high-frame-rate
contrast-enhanced US (HFR-CEUS) and particle image velocimetry (PIV), or US
velocimetry, in participants with aortoiliac stenosis. In this prospective
study, participants with a recently diagnosed aortoiliac stenosis underwent
HFR-CEUS measurements of the pre- and poststenotic vessel segments.
Two-dimensional quantification of blood flow was achieved by performing PIV
analysis, which was based on pairwise cross-correlation of the HFR-CEUS images.
Visual inspection of the entire data set was performed by five observers to
evaluate the ability of the technique to enable adequate visualization of blood
flow. The contrast-to-background ratio and average vector correlation were
calculated. In two participants who showed flow disturbances, the flow
complexity and vorticity were calculated. Results: 35 participants were
included. Visual scoring showed that flow quantification was achieved in 41 of
42 locations. In 25 locations, one or multiple issues occurred that limited
optimal flow quantification, including loss of correlation during systole,
shadow regions, a short vessel segment in the image plane, and loss of contrast
during diastole. In the remaining 16 locations, optimal quantification was
achieved. The contrast-to-background ratio was higher during systole than
during diastole, whereas the vector correlation was lower. Flow complexity and
vorticity were high in regions with disturbed flow. Blood flow quantification
with US velocimetry is feasible in patients with an aortoiliac stenosis, but
several challenges must be overcome before implementation into clinical
practice.
