Patients with wake-up strokes, strokes with unclear onset time, and witnessed late presenting strokes may potentially benefit from intra-arterial reperfusion therapy. However, an important indicator of whether subjects will benefit or not during this later time window is the confirmation of a large vessel occlusion (LVO), and assessment of the core infarct volume relative to the volume of salvageable penumbra. Therefore, standardized imaging selection of subjects is required for inclusion into the study.