Inclusion Criteria- Endovascular treatment can be initiated within 6 hours of symptom onset.
- ASPECTS of >=6 is diagnosed by two or more stroke physicians.
- The end diastolic velocity in the common carotid arteries or internal carotid artery is evaluated by carotid duplex ultrasound
- NIHSS score of >=6.
- Age>=18 years.
- Written informed consent is obtained.
Exclusion Criteria- Pre-stroke modified Rankin Scale (mRS) score >=2.
- Difficulties to evaluate ASPECTS on initial CT.
- Difficulties to groin puncture.
- History of severe allergic reaction to contrast medium.
- End stage renal disease.