Optimization Strategy of Carotid Artery Stenosis

The goal of this observational study is to learn about how to utilize multiple evaluation techniques in carotid artery stenosis patients for optimizing assessment of diagnosis and treatment strategy. The main questions it aims to answer are: * Identify best strategy that use multi-modal MRI and CT to assess patients' cerebral lesions and perfusion. * Identify best strategy that use multi-modal MRI, PET-MRI ultrasound and CT to assess components and characters of patients' carotid plaques. Participants will accept imaging examination before and after surgery. And doctors will collect basic characteristics, imaging results and biological samples of patients for analysis.