Morofuji Y, Horie N, Tateishi Y, et al. - Using digital subtraction angiography (DSA) as a gold standard, researchers ascertained if arterial spin labeling (ASL) MRI could be used to identify the occlusion site and collateral perfusion. From January 2012 to September 2014, they retrospectively reviewed data from 521 consecutive patients who presented with acute ischemic stroke at the institution. Data reported that the sensitivity and specificity, respectively, for identifying occlusion site with ASL were 82.8 and 100% and those for identifying collateral flow with ASL were 96.7 and 50%, respectively. The reliability of the inter-rater was excellent for the proximal intra-arterial sign (IAS) and significant for distal IAS detection. In patients with acute ischemic stroke, proximal IAS and distal IAS on ASL imaging can provide important diagnostic clues for detecting arterial occlusion sites and collateral perfusion.