MR-based Collateral Imaging to Predict Response to Endovascular Treatment of Stroke (FAST-COLL Study)

Inclusion Criteria: * Acute ischemic stroke * Age 20 years and older * Disabling stroke defined as a baseline NIHSS \> 5 at the time of arrival * Onset (last-seen-well) time to endovascular treatment time \< 12 hours * Confirmed symptomatic intracranial occlusion, based on CT or MR angiography, at one or more of the following locations: Carotid T/L, M1 MCA, or M1-MCA equivalent (2 or more M2-MCAs) * Signed informed consent or appropriate signed deferral of consent where approved Exclusion Criteria: * Baseline non-contrast CT reveals a moderate/large core defined as extensive early ischemic changes of ASPECTS 0-5 in the territory of symptomatic intracranial occlusion. * Clinical history, past imaging or clinical judgment suggests that the intracranial occlusion is chronic * Unable to undergo MRI (contraindicated or poor cooperation) * Patient has a severe or fatal comorbid illness that will prevent improvement or follow-up or that will render the procedure unlikely to benefit the patient * Pregnant females as determined by positive urine hCG test or lactating females