Patients scheduled for carotid endarterectomy undergo preoperative imaging to assess vulnerable plaque. The imaging modalities include (in various combinations at different study sites) 3-dimensional ultrasound, PET/CT imaging with fluorodeoxyglucose, MRI (3T)with gadolinium, and contrast ultrasound for assessment of neovascularity of plaques. At surgery the carotid endarterectomy is carried out with en bloc removal of the specimen, which is scanned and stained and assembled into 3D histology.