IntraCranial Angiography-derived Fraction Flow-guided Percutaneous Transluminal Angioplasty and Stenting Versus Medical Therapy (ICAS-MT)

1. Age ≥30 and ≤80 years old.
2. Symptomatic intracranial atherosclerotic stenosis: Transient ischemic attack (TIA) or stroke related to 70%-99% stenosis in the major intracranial arteries (intracranial segment of the internal carotid artery, M1 segment of the middle cerebral artery, V4 segment of the vertebral artery, and basilar artery) within the past 3 months.
3. Only one target vessel with 70-99% stenosis confirmed by angiography for enrollment in the trial (WASID criteria).
4. Patients with ischemic stroke should be performed with stenting beyond a duration of 2 weeks from the latest ischemic symptom onset, patients with TIA have no time restriction.
5. Pre-enrollment modified Rankin Scale (mRS) score ≤2.
6. Target vessel reference diameter must be measured to be 2 mm to 4.5 mm, target area of stenosis is less than or equal to 14mm in length.
7. Patients required to meet at least with one atherosclerotic risk factors, including hypertension, diabetes, hyperlipidemia, hyperhomocysteinemia, coronary heart disease, obesity, smoking history, and atherosclerosis in other arterial vessels.
8. Negative pregnancy test in a female who has had any menses in the last 18 months.
9. Patient is willing and able to return for all follow-up visits required by the protocol.
10. Patient understands the purpose and requirements of the study, can make him/herself understood, and has provided informed consent.

Exclusion Criteria:

1. Intracranial arterial stenosis not caused by atherosclerotic lesions, such as arterial dissection, moya-moya disease, vasculitic disease, viral vascular lesions (e.g., herpes zoster, varicella), neurosyphilis, other intracranial infections, radiation-induced vasculopathy, fibromuscular dysplasia, sickle cell disease, neurofibromatosis, benign central nervous system vascular diseases, postpartum angiopathy, suspected vasospastic process, suspected recanalized embolus, etc.
2. Any conditions that precludes proper angiographic assessment.
3. Preoperative MRI indicating only lacunar infarction in the target lesion territory.
4. History of subarachnoid hemorrhage, subdural or epidural hematoma within 30 days prior to enrollment, or untreated chronic subdural hematoma thickness≥5mm, or history of primary intracerebral hemorrhage.
5. At risk of hemorrhagic transformation during the procedure (CT or MRI showing infarct area diameter >5 cm); hemorrhagic transformation of an ischemic stroke within the past 15 days (detected by CT).
6. Tandem extracranial or intracranial stenosis (70%-99%) or occlusion that is proximal or distal to the target intracranial lesion
7. Bilateral intracranial vertebral artery stenosis of 70%-99% and uncertainty about which lesion is symptomatic (for example, if patient has pon, midbrain, temporal and occipital symptoms).
8. Stenting, angioplasty, or endarterectomy of an extracranial (carotid or vertebral artery) or intracranial artery within 30 days prior to expected enrollment date.
9. Previous treatment of target lesion with a stent, angioplasty, or other mechanical device, or plan to perform staged angioplasty followed by stenting of target lesion
10. Severe vascular tortuosity, severe calcification, or other factors that would preclude the safe introduction of a guiding catheter, guiding sheath or stent placement.
11. Presence of intraluminal thrombus proximal to or at the target lesion.
12. Any aneurysm proximal to or distal to intracranial stenotic artery.
13. Intracranial tumors or any intracranial vascular malformations.
14. Potential cardiac sources of emboli such as atrial fibrillation, left ventricular thrombus, heart valve replacement, atrial septal defect, ventricular septal defect, atrial myxoma, etc.
15. Myocardial infarction within previous 30 days.
16. Suspected severe allergy or contraindication to vascular interventional-related drugs or devices, such as aspirin, clopidogrel, general anesthesia agents, heparin, contrast agents, nitinol alloy, etc.
17. Active bleeding diathesis or coagulopathy, active gastrointestinal ulcer, major systemic hemorrhage within 30 days, active bleeding diathesis, platelets count \<100,000, hematocrit \<30, INR >1.5, dysfunctions of the blood coagulation system.
18. uncontrolled severe hypertension (systolic BP>180mm Hg or diastolic BP>110mm Hg)
19. Severe comorbidities or unstable conditions, such as severe heart failure, respiratory failure, or renal failure (serum creatinine>264μmol/L, unless on dialysis), severe liver dysfunction (ALT or ALT >3 times normal), malignant tumors.
20. Major surgery performed within 30 days prior to enrollment or planned inpatient surgery within 90 days after enrollment.
21. Pregnancy or intent to become pregnant during the trial period.
22. Currently participating in another clinical trial.
23. Life expectancy less than 3 years
24. Patients unable to complete follow-up due to cognitive impairment, emotional disorders, or mental illness.