Optical Coherence Tomography-Assisted Strategy for Interventional Management of Symptomatic Carotid Stenosis (OASIS-C)

Inclusion Criteria: 1. Age 20-80 years old. 2. Primary or recurrent symptomatic extracranial carotid artery stenosis (a recent TIA\[\<180 days\] or ischemic stroke \[14-180 days\] before enrollment attributed to 50-99% stenosis of extracranial carotid artery) receiving treatment with at least one antithrombotic drug and/or standard medical management of vascular risk factors. 3. Diagnosed by DSA: an extracranial carotid artery stenosis (50-99% according to NASCET method) with lesion length ≤ 10mm, diameter ≥ 1.5mm, and normal distal artery. (Regarding the curvature and angle of the lesion, whether the patient is enrolled per the investigator's determination based on the patient's situation ). 4. Informed consent signed. Exclusion Criteria: 1. Acute ischemic stroke onset within 14 days before enrollment. 2. Neurological deficits worsen within 24 hours before enrollment. 3. Baseline modified Rankin Scale ≥ 3. 4. Thrombolytic therapy within 24 hours before enrollment. 5. Previous ipsilateral endovascular treatment. 6. Intracranial hemorrhage within the past 3 months. 7. Any major surgery, major trauma, revascularization procedure, or acute coronary syndrome within 1 month before enrollment. 8. Major (non-carotid) surgery/procedures planned within 3 months after enrollment. 9. Gastrointestinal hemorrhage within 1 month prior to enrollment. 10. Allergic to heparin, aspirin, clopidogrel, contrast agents, anesthetics, and balloon components. 11. Platelet count \< 100,000/microliter or history of heparin-induced thrombocytopenia. 12. Severe dysfunction of liver (ALT \> three-fold higher than the upper limit of normal value or AST \> three-fold higher than the upper limit of normal value) or kidney (serum creatinine \> two-fold higher than the upper limit of normal value). 13. Non-atherosclerotic carotid stenosis (dissection, fibromuscular dysplasia, or stenosis following radiation therapy). 14. Intracranial arteries, target artery's supplying artery or contralateral carotid artery with 50-99% stenosis. 15. Coexistent with Intracranial tumors, aneurysms or arteriovenous malformations. 16. Tortuous vascular approach that cannot be stabilized to obtain vascular access. 17. Pregnant and lactating women. 18. Expected survival expectation is less than \< 6 months.