A quantitative vascular analysis system for evaluation of atherosclerotic lesions by MRI. An analysis package called QVAS (Quantitative Vascular Analysis System) is presented for the evaluation of atherosclerotic arterial lesions visualized in vivo by magnetic resonance imaging. QVAS permits interactive identification of vessel and lesion boundaries, segmentation of tissue classes within the lesion, quantitative analysis of lesion features, and three dimensional display of lesion structure. The performance of QVAS is demonstrated using images of carotid artery lesions.