QUANTIFICATION OF CAROTID BLOOD-FLOW VELOCITY USING MR PHASE MAPPING

Objective: 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 puls atility in normal subjects and patients with extracranial carotid dise ase. Materials and Methods: Using PM, we measured the systolic peak, m inimum diastolic, and mean CBFV and the pulsatility index in both comm on carotid arteries (CCAs) of 22 normal subjects and 32 patients. In a ddition, the CBFV was quantified in the internal carotid arteries (ICA s) of 25 patients. These data were compared with independent measureme nts based on pulsed-wave Doppler ultrasonography. Results: Correlation s between PM and pulsed-wave Doppler were strong for systolic peak CBF V in both the CCA (r = 0.91) and the ICA (r greater than or equal to 0 .82). Slightly lower correlations were obtained for mean CBFV (r great er than or equal to 0.79) and minimum diastolic CBFV (r greater than o r equal to 0.75), both measured in the CCA. Velocity waveform comparis on revealed high between-method correlations for the CCA (r = 0.90 for normals; r greater than or equal to 0.88 for patients) and slightly l ower correlations for the ICA (r greater than or equal to 0.75). Agree ment was lower (r = 0.63) for measurements in the ICA distal to high g rade stenosis. Conclusion: Phase mapping compared well with Doppler ul trasonography in quantifying CBFV and pulsatility in patients with ext racranial carotid artery disease. Except for poststenotic measurements in high grade obstructive lesions, PM is capable of providing quantit ative hemodynamic information on the severity of ICA stenosis.