Ultrasound velocimetry in patients with aortoiliac stents

Local flow patterns influence the patency of stents, while blood flow quantification in stents is challenging. This study aimed to investigate the feasibility of two-dimensional blood flow quantification using high-frame-rate, contrast–enhanced US (HFR-CEUS) and particle image velocimetry (PIV), or echoPIV, in patients with aortoiliac stents. HFR-CEUS measurements were performed at 129 locations in 62 patients. Two-dimensional blood flow velocity fields were constructed by pairwise cross-correlation of the HFR-CEUS images. Visual inspection was performed by five observers to evaluate feasibility. The contrast-to-background ratio and average vector correlation were calculated and compared between stented and native vessel segments. Flow quantification with echoPIV was possible in 128/129 locations (99%). Optimal quantification was achieved in 40/129 locations (31%). Partial quantification was achieved in 88/129 locations (68%), that suffered from one or multiple limiting issues, such as loss of correlation during systole (57/129), short vessel segments (20/129), loss of contrast during diastole (20/129) and shadow regions (20/129). The contrast-to-background ratio and vector correlation was lower in the stented vessel segments at the inflow region (compared to the native vessel), but higher at the outflow region, indicating that the stent does not affect these parameters. In conclusion, echoPIV is feasible in patients with aortoiliac stents.