Inclusion Criteria:  Over 30 years old; The patients with symptomatic (>50%) or asymptomatic carotid stenosis (> 70%) measured by computed tomography angiography (CTA) or B-mode ultrasonography CEA operation will be performed in our hospital.  Exclusion Criteria:  The history of CEA operation in the last 3 months; Diseases (AF, valve diseases, etc.) that may cause cardiac thrombosis; Contraindications of MR examination (vascular stent implantation, pacemaker, metal or magnetic plants in vivo, claustrophobia, etc.) were found; Contraindications of contrast agents: such as renal failure, iodine or gadolinium contrast agent allergy; Having heart or respiratory failure; Serious consciousness disorder (coma, etc.); Brain tumor; Acute cerebral hemorrhage; Pregnant women or planned pregnancies in the past 2 years; Who does not agree to sign the informed consent.