Comparative analysis of blood flow velocity in middle cerebral artery stenosis by transcranial doppler ultrasonography and contrast-enhanced high-resolution magnetic resonance imaging

BACKGROUND: This study aimed to investigate the optimal cutoff value of transcranial Doppler (TCD) ultrasonography for detecting middle cerebral artery (MCA) stenosis and differences in MCA blood flow velocities between plaques with different characteristics using contrast-enhanced high-resolution magnetic resonance imaging (CE-HR-MRI). METHODS: A total of 122 patients with MCA stenosis detected using TCD underwent CE-HR-MRI. Peak systolic velocity (PSV), mean flow velocity (MFV), and end-diastolic velocity (EDV) of the stenotic and distal segments were recorded. The stenotic/distal MFV ratio (SDR) was then calculated. Plaque characteristics were analyzed using CE-HR-MRI to compare differences in blood flow velocity between the plaques with different characteristics. RESULTS: The optimal cutoff values for detecting mild, moderate, and severe stenosis were PSV = 140 cm/s, EDV = 60 cm/s, and MFV = 90 cm/s; PSV = 200 cm/s, EDV = 90 cm/s, MFV = 120 cm/s, and SDR = 1.7; and PSV = 270 cm/s, EDV = 150 cm/s, MFV = 180 cm/s, and SDR = 3.0, respectively. The agreement between TCD and CE-HR-MRI was highest when using PSV (weighted kappa = 0.839). PSV, MFV, EDV, and SDR were significantly elevated in concentric plaques compared with those in eccentric plaques. Plaque enhancement grade 2 was significantly higher in PSV, MFV, and EDV than plaque enhancement grades 0 and 1. However, after stratification by stenosis severity, these differences were no longer significant. CONCLUSIONS: TCD, particularly PSV, provides reliable grading of MCA stenosis when referenced against CE-HR-MRI. Although higher flow velocities are observed in concentric plaques and those with grade 2 enhancement, these differences are not independent of stenosis severity. Nevertheless, the established velocity cutoffs for stenosis grading may facilitate non-invasive risk stratification in patients with MCA stenosis.