Perfusion Imaging Evaluation for Ischemic Stroke on 6-24 Hours Undergoing Endovascular Thrombectomy

Inclusion Criteria: Clinical Inclusion Criteria:

1. Clinical signs and symptoms consistent with the diagnosis of an acute ischemic stroke
2. Age ≥18 years
3. NIHSS ≥ 6
4. Endovascular thrombectomy can be initiated (femoral puncture) between 6 and 24 hoursafter time last know well
5. No significant pre-stroke disability (pre-stroke mRS must be ≤ 3 )
6. Patient/Legally Authorized Representative has signed the Informed Consent form Imaging Inclusion Criteria:
7. ICA or MCA-M1 or MCA-M2 or BA occlusion (carotid occlusions can be cervical orintracranial with or without tandem MCA lesions) as evidenced by MRA or 4D-CTA
8. Target Mismatch Profile on CT perfusion or MR perfusion: ischemic core volume is ≤ 70ml, mismatch ratio is >/= 1.2 )

Exclusion Criteria: Clinical Exclusion Criteria:

1. Other serious, advanced, or terminal illness (investigator judgment) or lifeexpectancy is less than 90 days
2. Subject with a co-morbid disease or condition that would confound the neurological andfunctional evaluations or compromise survival or ability to complete follow-upassessments
3. Unable to undergo a contrast brain perfusion scan with either MRI or CT
4. Pregnant
5. Known serious sensitivity to radiographic contrast agents
6. Treated with rtPA >6 hours after time last known well
7. Known hereditary or acquired hemorrhagic diathesis, coagulation factor deficiency;recent oral anticoagulant therapy with INR > 3 (recent use of one of the new oralanticoagulants is not an exclusion if estimated GFR > 30 ml/min).
8. Seizures at stroke onset if it precludes obtaining an accurate baseline NIHSS
9. Current participation in another investigational drug or device treatment study
10. Known hereditary or acquired hemorrhagic diathesis, coagulation factor deficiency
11. Any other condition that, in the opinion of the investigator, precludes anendovascular procedure or poses a significant hazard to the subject if an endovascularprocedure was performed. Neuroimaging Exclusion Criteria:
12. ASPECTS score <6 on non-contrast CT (if patient is enrolled based on CT perfusioncriteria)
13. Evidence of intracranial tumor (except small meningioma), acute intracranialhemorrhage, neoplasm, subarachnoid hemorrhage, or arteriovenous malformation
14. Significant mass effect with midline shift
15. Evidence of internal carotid artery dissection
16. Intracranial stent implanted in the same vascular territory, known history of arterialtortuosity, and/or other arterial disease that precludes the safe deployment/removalof the thrombectomy device