- CT scan or MRI with evidence of: Mass effect or intracranial tumor, or hypodensity on unenhanced CT and cerebral blood volume (CBV) drop on CBV maps on Computed Tomography Perfusion (CTP), or, alternatively as per institutional standard, restricted diffusion on Diffusion weighted imaging (DWI) with an Alberta Stroke Program Early CT score (ASPECTs) of 6 or less