Inclusion Criteria:  age: 18-80; ischemic stroke confirmed by brain CT or MRI the time from onset to treatment: 4.5-6 hours NIHSS≥4 prestroke mRS≤1 signed informed consent  Exclusion Criteria:  prestroke mRS≥2 planned endovascular treatment planned intravenous thrombolysis based on WAKE-UP or EXTEND study criterion any contraindiction of intravenous thrombolysis other unsuitable conditions judged by investigator