Using advanced MRI techniques for patient selection before acute stroke therapy.

OPINION STATEMENT: Results of acute MRI studies may help guide the management of acute stroke. Patients with a malignant MRI pattern may be poor candidates for reperfusion therapies yet may benefit from hemicraniectomy. Preliminary data suggest that patients with a carefully identified diffusion weighted imaging (DWI)/perfusion weighted imaging (PWI) mismatch may benefit from intravenous recombinant tissue plasminogen activator in a 3- to 6-hour time window; however, confirmatory studies with larger sample sizes are required before clinical use of this strategy can be generally recommended. Post hoc analyses of recent studies suggest that PWI techniques that use a threshold to exclude benign oligemia from penumbra and DWI techniques that use apparent diffusion coefficient thresholds to exclude reversible DWI lesions to distinguish the ischemic core from penumbra appear to provide more accurate determinations of the volume of salvageable tissue. New automated software programs are now implementing these techniques to generate quantitative PWI and DWI maps within minutes. Prospective trials are in progress to investigate these new techniques. The results of these studies will further refine the application of MRI to select patients for acute recanalization therapies.