Quantification of carotid blood flow velocity using MR phase mapping

The purpose of this study was to determine the feasibility of a two-dimensional phase-sensitive MR technique [phase mapping (PM)] for the quantification of carotid blood flow velocity (CBFV) and pulsatility in normal subjects and patients with extracranial carotid disease.

Using PM, we measured the systolic peak, minimum diastolic, and mean CBFV and the pulsatility index in both common carotid arteries (CCAs) of 22 normal subjects and 32 patients. In addition, the CBFV was quantified in the internal carotid arteries (ICAs) of 25 patients. These data were compared with independent measurements based on pulsed-wave Doppler ultrasonography.

Correlations between PM and pulsed-wave Doppler were strong for systolic peak CBFV in both the CCA (r = 0.91) and the ICA (r > or = 0.82). Slightly lower correlations were obtained for mean CBFV (r > or = 0.79) and minimum diastolic CBFV (r > or = 0.75), both measured in the CCA. Velocity waveform comparison revealed high between-method correlations for the CCA (r = 0.90 for normals; r > or = 0.88 for patients) and slightly lower correlations for the ICA (r > or = 0.75). Agreement was lower (r = 0.63) for measurements in the ICA distal to high grade stenosis.

Phase mapping compared well with Doppler ultrasonography in quantifying CBFV and pulsatility in patients with extracranial carotid artery disease. Except for poststenotic measurements in high grade obstructive lesions, PM is capable of providing quantitative hemodynamic information on the severity of ICA stenosis.