The investigators hypothesize that in vivo MRI and/or CT examinations of patients, when suitably acquired and analyzed with the vascuCAP™ analysis software, can provide a sufficiently accurate profile of plaque characteristics to provide an objective basis for patient management. Study subjects include patients undergoing endarterectomies to mitigate their clinical risk or symptoms for conditions including stroke, claudication, and critical limb ischemia. The endarterectomy specimens removed at surgery will allow a direct comparison between the MRI information obtained prior to the surgery and the histopathological analyses of the arterial specimens. The vascuCAP™ measurements of structural and functional features of the arterial wall will be performed in patients undergoing endarterectomy. Measured results will be compared in a blinded fashion with histology to assess performance of plaque profiling and build a pilot prediction model for risk scoring.