Carotid artery stenosis: clinical efficacy of MR phase-contrast flow quantification as an adjunct to MR angiography.

Abstract

To assess the utility of magnetic resonance (MR) flow quantification in the evaluation of suspected carotid artery stenosis. Fifty-five patients referred for angiography and 10 healthy volunteers underwent Doppler ultrasound, three-dimensional time-of-flight MR angiography, and MR phase-contrast flow quantification to measure peak systolic velocity (PSV) and volumetric flow rate (VFR) in the common and internal carotid arteries distal to the stenosis. PSV and VFR were significantly lower in the severely (> or = 70%) stenosed internal carotid arteries (P < .05). The VFR ratio (internal carotid artery-common carotid artery) achieved 91% overall accuracy for detection of severe stenosis. Combination of flow data with results of MR angiography yielded sensitivity of 100% (95% confidence interval, 78%-100%) with a modest loss in specificity. Doppler and MR measurements of PSV in the common carotid artery showed significant correlation: volunteers, r = .73; patients, r = .64. MR flow quantification provides information about the hemodynamic significance of carotid stenosis. As an adjunct to MR angiography, it may be useful in enabling differentiation of occlusions from critical stenoses.