Precise evaluation of blood flow patterns in human carotid bifurcation based on high‐frame‐rate vector flow imaging

Purpose To investigate the feasibility of high‐frame‐rate vector flow imaging (HiFR‐VFI) compared to ultrasound color Doppler flow imaging (CDFI) for precisely evaluating flow characteristics in the carotid bifurcation (CB) of presumed healthy adults. Methods Forty‐three volunteers were assessed for flow characteristics and their extensions using HiFR‐VFI and CDFI in CBs. The flow patterns were classified according to the streamlines in HiFR‐VFI and quantitatively measured using an innovative turbulence index (Tur‐value). Interobserver agreement was also assessed. Results HiFR‐VFI was consistent with CDFI in detecting laminar and nonlaminar flow in 81.4% of the cases; however, in 18.6% of the cases, only HiFR‐VFI identified the nonlaminar flow. HiFR‐VFI showed a larger extension of complex flow (0.37 ± 0.26 cm 2 ) compared to CDFI (0.22 ± 0.21 cm 2 ; p < 0.05). The flow patterns were classified into four types: 3 type‐I (laminar flow), 35 type‐II (rotational flow), 27 type‐III (reversed flow), and 5 type‐IV (complex flow). The Tur‐value of type‐IV (50.03 ± 14.97)% is larger than type‐III (44.57 ± 8.89)%, type‐II (16.30 ± 8.16)%, and type‐I (1.48 ± 1.43)% ( p < 0.05). Two radiologists demonstrated almost perfect interobserver agreement on recognizing the change of streamlines (κ = 0.81, p < 0.001). The intraclass correlation coefficient of the Tur‐value was 0.98. Conclusion HiFR‐VFI can reliably characterize complex hemodynamics with quantitative turbulence measurement and may be an auxiliary diagnostic tool for assessing atherosclerotic arterial disease.