The need for early accurate diagnosis of AIS has motivated the development of new advanced imaging techniques for the early diagnosis of the condition and the selection of patients who might present outside the window for systemic thrombolytic therapy. During the last decade, the state of art imaging techniques has developed for the imaging of patients with hyperacute stroke including both angiographic and perfusion imaging.



The imaging modalities, which are in widespread use in primary stroke imaging include; computed tomography and magnetic resonance imaging. Imaging can be categorized into structural imaging, vascular imaging and perfusion imaging. Important signs of early stroke on brain CT include; insular ribbon sign, the hypedense artery sign, and the development of hypo-attenuation lesions. MRI is more sensitive than CT for the demonstration of these lesions especially diffusion weighted images which are currently the gold standard for the evaluation of the extent of infarct core. Susceptibility weighted images are highly sensitive for the demonstration of hyperacute bleed within the infarct.



CT and MR angiography are highly sensitive for the demonstration of large vessel occlusion which is very important for selection of patients for endovascular treatment.


Perfusion studies can be performed using CT or MRI and are showing an increasing role in the identification of salvageable brain tissue (penumbra) and target mismatch between hypoperfused volume and infarct core, an important criterion for selection of patient who might benefit from endovascular treatment.