Echoplanar Imaging Thrombolysis Evaluation Trial (EPITHET)

Inclusion Criteria: * Patients who present: * with acute hemispheric stroke within 3-6 hours of onset, * have at least moderate limb weakness, * a National Institute of Health Stroke Scale (NIHSS) score \> 4, * had a pre-stroke modified Rankin Scale (MRS) score of 0 - 2 * and who are able to undergo CT and MRI, are eligible for this study. Exclusion Criteria: * Females who are pregnant or breast-feeding, * persons who have CT-verified hemorrhagic stroke, major ischemia ( \> 33% of the middle cerebral artery (MCA) territory infarcted), subarachnoid hemorrhage, arteriovenous malformation, aneurysm, intracranial neoplasm that is terminal or poses a risk of hemorrhage , * are comatose or severely obtunded with fixed eye deviation and complete hemiplegia, * have had another stroke within the past 6 weeks, * have had a seizure prior to the administration of the study drug, * have active peptic ulceration, bleeding diatheses, previous intracerebral hemorrhage, * blood pressure \> 185/110, * major surgery or trauma within the past 30 days, or any other contraindications to tPA * have a presumed septic embolus or a myocardial infarction within the past 30 days * blood glucose values are \< 2.8 or \> 22.0 mmol/L, * pacemakers, aneurysm clips, implanted devices, claustrophobia, or any other contraindications to MRI, * decreased consciousness, * rapid clinical improvement, * confounding neurological condition (e.g. dementia), * any other life-threatening illness, or who are participating in another clinical trial, will be excluded from this study.