Inclusion Criteria1. Patient presenting to the emergency department with symptoms consistent with ischemic stroke.
2. Age > 18 yrs.
3. Baseline imaging including multi-phase CTA done within 12 hours of stroke symptom onset and initiated before recanalization therapy.
4. Evidence of a visible and symptomatic intracranial occlusion on baseline CT-angiography (intracranial ICA, M1 MCA segment +/- intracranial ICA, proximal M2 MCA).
5. Treatment with IV tPA and/or IA therapy.
Exclusion Criteria1. Intracranial hemorrhage (ICH) identified on baseline CT.
2. Previous moderate to large stroke in the ipsilesional hemisphere.
3. Modified Rankin Scale > 2 at baseline.
4. Unable to have CT-angio performed due to recent estimated creatinine clearance eCCr<60 ml/min, contrast allergy or other reasons.
5. Participation in another study that results in the patient receiving an investigational drug or therapy.
6. Any terminal illness (patient not expected to survive > 1 year).