Computed Tomography Angiogram Derived From Computed Tomography Perfusion Done With Low Iodine Volume Protocol Preserves Diagnostic Yield for Middle Cerebral Artery-M2 Occlusions

Abstract Background: Computed tomography angiogram (CTA) derived from computed tomography perfusion (CTP) has been proposed to avoid addition of separate CT perfusion protocol for selection of large vessel occlusion in acute stroke patients. Previous studies have validated this technique for proximal large vessel occlusions. In this study, we test reliability for identifying M2 occlusions on CTA derived from CTP. Methods: Through a retrospective search of the institutional thrombectomy database, we identified 28 cases with M2-MCA occlusion, of which 24 met the inclusion criteria for analysis. An additional 20 cases without M2-MCA occlusion (either normal or M1-MCA occlusion) were randomly mixed in the database to reduce observer bias. The baseline images of the CTP study in these 48 cases were then independently analyzed by 3 readers with varying level of expertise. The digital subtraction angiography (DSA) images were also independently reviewed where available. The percentage of agreement among reviewers as well as the probability of agreement of the reviewers, when compared to the DSA findings was also calculated. Results: The observed agreement for the image quality amongst the 3 readers (n = 48) varied between 0.78 and 0.95 and tended to be higher for the M1 segment MCA and lower for distal M2-MCA. The observed agreements comparing 3 image reviewers versus DSA in M2 patients (n = 24) was 98% for identifying occlusion (95% CI 95%-100%), 94% for identifying proximal M2 occlusion (95% CI 88%-98%), and 91% (95% CI 84%-97%) and 90% (95% CI 83%-95%), respectively for correctly identifying inferior and superior branch of M2 occlusion. Conclusion: CTA data derived from CT Perfusion study preserves diagnostic yield for correctly identifying M2 occlusion.