• It is incumbent that emergency physicians be aware of and utilize as appropriate all available tools in the critical, yet challenging evaluation and management of acute ischemic stroke (AIS) patients.
   
• While non-contrast head CT remains the primary modality used in the initial evaluation of these patients, CT angiography (CTA) and MRI with diffusion are rapidly becoming more acutely available because they provide more exact and accurate information, which directly affects the crucial decisions that have to be made in order to provide effective and expedient care.
   
• CTA provides imaging of the entire intra and extra cranial circulation beginning at the aortic arch to the Circle of Willis, and can be performed in less than 20 seconds.  Within minutes, these imags can be re-constructed to reveal vascular stenosis and occlusions.
   
• MRI is typically not as rapidly accessible as CT, but there are scenarios wherein the additional time spent to acquire this modaility yields significant clinical merit.  While a full brain MRI may take up to an hour, acquisition of the MR diffusion portion of the scan (which highlights focal areas of acute infarct) requires less than 10 minutes.    

References

1. Pancioli A.  "The Latest Treatment of Acute Stroke:  New Data and Clinical Practice Pearls."  Advancing the Standard of Care:  Cardiovascular and Neurovascular Emergencies. March 2009;39-44.
2. Srinivasan A., et al.  "State-of-the-art Imaging of Acute Stroke."  Radiographics 2006;26:S75-S95.
3. Verro P., et al.  "Clinical Application of CT Angiography in Acute Ischemic Stroke."  Clinical Neurological Neurosurgery. 2007;109:138-45.