Shi F, et al. - In patients with acute ischemic stroke (AIS), researchers developed a quantitative assessment of collateral perfusion at CT and examined its value in the prediction of outcome. They reviewed data from consecutive patients with AIS and an occluded M1 segment of the middle cerebral artery who underwent pretreatment perfusion CT between May 2009 and August 2017. The final analysis consisted of 204 patients. The results obtained from this retrospective study indicate that the measurement of maximum cerebral blood flow of collateral vessels within the Sylvian fissure is a feasible quantitative collateral assessment at perfusion CT. In patients with acute ischemic stroke, maximum cerebral blood flow of collateral vessels was linked to clinical result.