Inclusion Criteria

   1. Age 18 and older

   2. Clinical diagnosis of ischemic stroke and an associated score on the NIHSS of 5 or
   more points

   3. Planned to undergo (or has undergone) intra-arterial (IA) thrombectomy and/or
   thrombolysis for acute hemispheric stroke. (Either as primary therapy or as adjuvant
   therapy following intravenous tPA treatment)

   4. Planned to undergo or has undergone an MR brain scan including MR perfusion imaging
   (ASL & bolus PWI) and MR angiography of the circle of Willis prior to IA therapy

   5. Intra-arterial thrombectomy can be started within 90 minutes of completion of the MR
   perfusion scan and within 24 hours of symptom onset (Start of IA therapy is defined as
   the time of insertion of the femoral artery sheath; Time of brain scan is defined as
   the time that the scan is completed)

   6. Able to obtain informed consent

Exclusion Criteria

   1. Any pre-existing illness resulting in a modified Rankin Scale Score of 2 or higher
   prior to the qualifying stroke

   2. Creatinine clearance < 40 ml/min based on the NIDDK four-variable MDRD method
   (non-weight based)

   3. Documented allergy to MR contrast agent

   4. MRI contraindications (pacemaker, etc.)

   5. Pregnancy