Inclusion Criteria:  Age 18 - 95. Clinical signs consistent with acute ischemic stroke. Prestroke Modified Rankin Score ≤ 2 Consent obtained within 24 hours from last known well. Thrombolysis in Cerebral Infarction (TICI) 0-1 flow in The M1 or M2 segment of the middle cerebral artery (MCA), A1 or A2 segment of the anterior cerebral artery (ACA), or carotid terminus confirmed by CT or MR angiography; or the vertebral artery, basilar artery, posterior cerebral artery.  For patients with anterior LVO within 6 to 16 hours of last known normal, the imaging criteria to meet: ischemic core less than 70 ml,mismatch ratio of 1.8 or more, and a penumbra of 15 ml or more. For patients with anterior LVO within 6 to 24 hours of last known normal, following criteria: age ≥80 years，NIHSS≥10，infarct volume of less than 21 ml；age ≤80 years，NIHSS≥10，infarct volume of less than 31 ml；age ≤80 years，NIHSS≥20，infarct volume of less than 51 ml.  For patients with posterior LVO, time of onset to admission is within 24 hours.  Subject is willing to conduct protocol-required follow-up visits. Subject or subject's legally authorized representative has signed and dated an Informed consent Form.  Exclusion Criteria:  Female who is pregnant. Serious sensitivity to radiographic contrast agents. Computed tomography (CT) or Magnetic Resonance Imaging (MRI) evidence of hemorrhage on presentation. Warfarin therapy with international normalized ratio(INR) greater than 1.7. Low molecular Weight Heparins, Heparin, Factor Xa inhibitors or direct thrombin inhibitors as full dose within the last 48 hours. Baseline lab values: glucose <50 mg/dL or > 400 mg/dL, platelets < 100,000 Life expectancy of less than 90 days.