The implications of magnetic resonance angiography artifacts caused by different types of intracranial flow diverters

Background: Serial cerebral angiographic imaging is necessary to ensure cerebral aneurysm occlusion after flow diverter placement. Time-of-flight (TOF)-magnetic resonance angiography (MRA) is used for this purpose due to its lack of radiation, contrast media and complications. The comparative diagnostic yield of TOF-MRA for different flow diverters has not been previously analyzed. Purpose: To evaluate the diagnostic accuracy of TOF-MRA in cerebral aneurysms treated w divertersith different flow diverters. Materials and Methods: Flow-diverted patients whose cerebral follow-up MRA and digital subtraction angiograms (DSA) were obtained within 6 weeks were retrospectively identified. The DSA (as gold standard) and MRA images of these patients were compared by two readers (blinded to both patient data and endovascular procedure data) for residual aneurysms and the status of the parent artery for each type of flow diverter. In a second group of patients, magnetic susceptibility artifacts were manually measured and compared for different FDs. Results: Seventy-six patients (85 aneurysms) were included in group one, and 86 patients (95 aneurysms) were included in group 2. TOF-MRA and DSA showed almost perfect agreement for residual aneurysms (kappa=0.88, p < 0.001) (positive predictive value (PPV)=1.00, specificity=1.00, negative predictive value (NPV)=0.89, sensitivity=0.89). Intermodality agreement (kappa=0.97 vs. kappa=0.74, p