Reliability and accuracy of 3-mm and 2-mm maximum intensity projection CT angiography to detect intracranial large vessel occlusion in patients with acute anterior cerebral circulation stroke

Purpose: To evaluate the reliability and accuracy of thick maximum intensity projection (MIP) CTA images to detect large-vessel occlusion (LVO) in the anterior circulation in patients with acute stroke. Methods: A total of 140 acute stroke patients (41 with and 99 without LVO) were evaluated by two neuroradiologists for LVO using axial 3-mm and 2-mm MIPs. Results: Interobserver agreement was substantial using 3-mm MIPs (ĸ = 0.67) and almost perfect using 2-mm MIPs (ĸ = 0.82). Using 3-mm MIPs, sensitivities were 80.5% and 68.3%, with specificities of 98.0% and 96.0%. Using 2-mm MIPs, sensitivities were 82.9% and 73.2%, with specificities of 98.0% and 99.0%. Sensitivity and specificity of 3 mm and 2 mm MIPs were not statistically significantly different (P ≥ 0.375). The majority of LVOs in the distal intracranial carotid artery, and/or M1-segment were correctly identified: 96.0% (observer 1, 3-mm MIPs), 88.0% (observer 2, 3-mm MIPs), 96.0% (observer 1, 2-mm MIPs), and 96.0% (observer 2, 2 mm MIPs). Using 3-mm MIP images, observers 1 and 2 missed 7/15 (46.7%) and 9/15 (60.0%) of isolated M2-segment occlusions, respectively. Using 2-mm MIP images, observers 1 and 2 missed 5/15 (33.3%) and 6/15 (40.0%) of isolated M2-segment occlusions, respectively. Conclusion: Thick (2–3 mm) axial MIPs are not useful to detect proximal LVO in the anterior circulation.