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Objective: The “delayed vessel sign” refers to the presence of relative unilateral delayed enhancement of a vessel or vessels in the anterior circulation on delayed phases of a multiphase CTA (MPCTA) distal to the point of vessel occlusion. We aimed to determine if educating radiologists on the “delayed vessel sign” would improve sensitivity, confidence and speed in the detection of distal anterior circulation vessel occlusions in the suspected stroke patient.Methods: Non-contrast CT (NCCT) and MPCTA studies of 53 individual patients, who presented with signs/symptoms of acute anterior circulation stroke, were retrospectively selected by an independent radiologist. 15 cases without a vessel occlusion, 15 cases with a M1 occlusion and 23 cases with a distal anterior circulation (A2/M2/M3) occlusion were included. Initially, NCCT and single phase CTA (SPCTA) studies were independently interpreted by four observers (two neuroradiologists, two radiology trainees) and observers’ confidence (scale 1-5), speed and sensitivity of detection were recorded. Observers were then educated on the “delayed vessel sign” and each study was re-examined after an interval of at least 14 days.Results: There was a significant improvement in the sensitivity of detection of distal anterior circulation vessel occlusions on MPCTA compared to SPCTA (p=0.0003) and this was also true for M1 occlusions (p=0.045). Overall confidence was 4.0 for SPCTA and 4.88 with MPCTA (p<0.0001). Average time taken to interpret each case on SPCTA was 85.5s and decreased to 40.1s with MPCTA (p<0.0001).Conclusion: The “delayed vessel sign” is a reliable indicator of ipsilateral vessel occlusion, and is particularly useful in cases involving distal MCA branches where the occlusion is not easily identified on the initial angiographic phase. We have found this sign facilitates the rapid on-table confirmation of acute ischemic stroke, even when small vessels are involved and the clinical diagnosis is uncertain.