Imaging of acute ischemic stroke.

For decades, imaging has been a critical component of the diagnostic evaluation and management of patients suspected of acute ischemic stroke (AIS). With each new advance in the treatment of AIS, the role of imaging has expanded in scope, sophistication, and importance in selecting patients who stand to benefit from potential therapies. Although the field of stroke imaging has been evolving for many years, there have been several major recent changes. Most notably, in late 2017, the window for treatment expanded to 24 h from onset of stroke symptoms in selected patients. Furthermore, for those patients in expanded time windows, guidelines issued in early 2018 now recommend the use of "advanced" imaging techniques in the acute setting, including CT perfusion and MRI, to guide therapeutic decision-making. With these and other changes, the emergency radiologist must be prepared to handle a growing volume and complexity of AIS imaging. This article reviews the various imaging modalities and techniques employed in the imaging of AIS patients, with an emphasis on recommendations from recent randomized controlled trials and national consensus guidelines.