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

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.

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.

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 cm² ) compared to CDFI (0.22 ± 0.21 cm² ; 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.

HiFR-VFI can reliably characterize complex hemodynamics with quantitative turbulence measurement and may be an auxiliary diagnostic tool for assessing atherosclerotic arterial disease.