Abstract W MP15: A Novel Magnetic Resonance Imaging Approach for Collateral Flow Imaging in Ischemic Stroke

Abstract

Background: Assessing the status of collateral circulation is important in acute ischemic stroke. However, digital subtraction angiography(DSA) which is considered as the gold standard for evaluation of collaterals is invasive and has a risk of thrombotic complications. Dedicated MRI sequences for evaluation of collateral flow can be generated using perfusion-weighted imaging(PWI) source data. We compared a novel collateral flow imaging technique with DSA for determining collateral circulation in the setting of acute stroke. Methods: Consecutive patients who were eligible for recanalization therapy underwent MRI and DSA for acute MCA infarction at a university medical center. A collateral flow map derived from PWI source data was generated by manual or semi-automatic post-processing. Collateral grading based on collateral flow map was performed and compared with DSA (Figure). Results: Of 68 patients, 42(61.8%) had M1 occlusion and 26(38.2%) had ICA occlusion. The time interval between MRI scanning and the start of DSA was 50.8±28.6 minutes. Both the collateral flow map and DSA showed good inter-observer agreement of collateral grade(weighted κ-coefficients=0.817 for collateral flow map and 0.757 for DSA). There was good correlation between MRI- and DSA-based collateral grades: 68% had the same grade in the same patient(weighted κ-coefficient=0.653). In most patients who had mismatches between the two modalities, the collateral grade was higher in MRI-based vs. DSA-based assessment. Conclusion: MRI techniques for assessment of collaterals are rapidly being developed, which may provide insight on collateral perfusion in patients who are not otherwise candidates for conventional angiography and may potentially replace it in the future. Figure . Typical examples of collateral flow map- (left panel) and digital subtraction angiography (right panel)-based collateral grade. All DSAs show proximal MCA occlusions (white arrows).