Functional CT and MR imaging for evaluation of acute stroke.

When a patient arrives with symptoms of stroke, prompt imaging is a vital part of the work-up. For patients with ischemic stroke, thrombolytic therapy with intravenous tissue plasminogen activator (t-PA) must be given within the first 3 hours and intra-arterial thrombolytic therapy must be administered within 6 hours after the onset of symptoms to be effective. Late therapy limits the efficacy of treatment and increases the likelihood of brain edema and hemorrhage, which may be life threatening. Therefore, the potential benefits of recanalization must be weighed against the risks of increased morbidity and mortality. CT and MR imaging now play a significant role not only for diagnosis but also for assessing the volume of ischemic damage and amount of residual perfusion. This data, although still under investigation, plays a role in decision making on whether it is appropriate to give the patient thrombolytic treatment.