Vector Flow Imaging Compared with Digital Subtraction Angiography for Stenosis Assessment in the Superficial Femoral Artery – A Study of Vector Concentration, Velocity Ratio and Stenosis Degree Percentage

Abstract

Stenosis of the superficial femoral artery (SFA) induces complex blood flow with increased velocities. Disease assessment is performed with Doppler ultrasound and digital subtraction angiography (DSA), but Doppler ultrasound is limited by angle dependency and DSA by ionizing radiation. An alternative is the vector flow imaging method based on transverse oscillation (TO), an angle-independent vector velocity technique using ultrasound. In this study, flow complexity and velocity measured with TO were compared with DSA for the assessment of stenosis in the SFA.The vector concentration, a measure of flow complexity, and the velocity ratio obtained from the stenosis and a disease-free adjacent vessel segment, were estimated with TO in 11 patients with a total of 16 stenoses of the SFA. TO data were compared with the corresponding stenosis degree percentage obtained with DSA.The correlation between the vector concentration and DSA was very strong (R=0.93; p<0.001; 95% confidence interval (CI): 0.81–0.98), while only moderate for velocity ratio and DSA (R=0.50; p<0.07; 95% CI: 0.00–0.80). The correlation coefficients that were found were significantly different (p<0.005) without overlapping CI.The study indicated that flow changes in the SFA induced by stenosis can be quantified with TO, and that stenosis grading may be improved by estimation of flow complexity instead of velocity ratio. TO is a potential diagnostic tool for the assessment of atherosclerosis and peripheral arterial disease.

Vector Concentration used for Stenosis Assessment in the Carotid Artery before and after Carotid Stenting

“…VC was able to identify significant stenosis in the carotid artery and stent flow, with DSA used as reference. The results in this study are in line with previous studies with VC for flow assessment [15,16].…”

“…VC has several advantages compared to peak velocity estimation with spectral Doppler. Calcified plaques in the vessel wall of the carotid artery may hinder the evaluation of blood flow with ultrasound, since the flow can be hidden by shadows impeding peak flow alignment for peak velocity estimation [15]. VC is not dependent on alignment, since flows from all directions in the ROI are used to quantify the flow.…”

“…VC goes towards 1 in laminar flow and towards 0 for complex flow. Previous papers provide detailed explanations of the VC calculation [13,15,18].…”

“…Besides velocity estimation, VFI can be applied for vector concentration (VC) estimation, a VFI derived parameter for flow complexity assessment [13]. Complex flow defined with vector flow has been connected with difference in the diameters of the carotid artery [14], and VC correlated strongly with DSA for stenosis degree assessment of the superficial femoral artery [15], and to peak velocities obtained with transesophageal echocardiography for evaluation of aortic valve stenosis [16].…”

Vector Flow Imaging of the Ascending Aorta in Patients with Tricuspid and Bicuspid Aortic Valve Stenosis Treated with Biological and Mechanical Implants

“…VC is a novel parameter for flow assessment correlating strongly to PSV for aortic flow and useful for stenosis assessment (Hansen et al 2015(Hansen et al , 2016b(Hansen et al , 2017. A recent study reported that VC was a stronger predictor than velocity ratio for stenosis assessment in the femoral artery compared with angiography (Hansen et al 2019). In this study, it was found that patients with bicuspid AS had more complex flow than patients with tricuspid AS.…”