Comparison of multimodal CT scan protocols used for decision-making on mechanical thrombectomy in acute ischemic stroke

Different CT-based protocols are being used in acute ischemic stroke. We aimed to assess the added value of delayed-phase CT angiography (CTA) and CT perfusion (CTP) to a basic protocol using non-contrast computerized tomography (NCCT) with arterial-phase CTA in patient selection for mechanical thrombectomy. We retrospectively included consecutive acute ischemic stroke patients with a symptomatic intracranial arterial occlusion between January 2015 and November 2016 who underwent NCCT, arterial and delayed-phase CTA, and CTP. These imaging studies were grouped into five protocols: (1) NCCT and arterial-phase CTA; (2) NCCT, arterial-phase CTA, and CTP; (3) NCCT, arterial- and delayed-phase CTA; (4) NCCT, arterial- and delayed-phase CTA, and CTP; and (5) NCCT and delayed-phase CTA. Two interventional neuro-radiologists independently decided on mechanical thrombectomy for each patient based on the protocols. They reached consensus for discrepant decisions. We assessed the raters' confidence level, inter-rater agreement, and compared treatment decisions for the different protocols. We included 73 patients (44% male, mean age 74). The inter-rater agreement was substantial for protocols with three or more modalities (ҡ = 0.613–0.704) and moderate for two-modality protocols (ҡ = 0.506–0.529). The highest agreement and confidence level was achieved for the combination of NCCT, arterial-phase CTA, and CTP. Adding CTP to NCCT and arterial-phase CTA resulted in a 10% increase of recommendations for mechanical thrombectomy and adding delayed-phase CTA resulted in a 4% increase. These management changes did not reach statistical significance (p = 0.07; p = 0.25, respectively). Adding CTP and/or a delayed-phase CTA to NCCT with arterial-phase CTA improves the decision-maker's confidence level and creates a trend towards a lower threshold for mechanical thrombectomy.