[Fundamentals of Therapy for Acute Ischemic Stroke:Basic Knowledge for the Practical Assessment of Eligibility]

Acute ischemic stroke (AIS) requires rapid and appropriate imaging techniques to guide reperfusion therapy. This article provides a practical approach for the neuroimaging interpretation of AIS, focusing on the evaluation and integration of imaging findings into clinical decision-making. In MRI-first settings, diffusion-weighted imaging is applied first to identify acute ischemic lesions, followed by magnetic resonance angiography to identify the responsible vessel, with FLAIR and T2*-weighted imaging providing complementary information on lesion evolution, hemodynamics, and hemorrhagic findings. In CT-first settings, noncontrast CT, CT angiography, and CT perfusion are used to assess hemorrhage, early ischemic changes, vessel occlusion, collateral circulation, and tissue perfusion. Perfusion imaging can further estimate the ischemic core and hypoperfused tissue; however, automated results should not be interpreted in isolation. Understanding the characteristics and limitations of each imaging modality and integrating the imaging findings with neurological symptoms and time courses are essential to ensure the appropriate selection of reperfusion therapy.