Underestimation of Follow-Up Infarct Volume by Acute CT Perfusion Imaging.

Background And Objectives: It is unknown whether acute CT perfusion (CTP) core imaging may underestimate the follow-up infarct. We hypothesize that infarct underestimation occurs especially in late-presenting patients and that underestimated infarct can partially be detected on baseline noncontrast CT (NCCT).

Methods: We included patients with acute anterior circulation ischemic stroke who underwent baseline NCCT and CTP imaging, complete endovascular reperfusion, and follow-up MRI from the Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke (DEFUSE 3) trial and a consecutive, monocenter cohort. We divided patients into early (<6 hours) and late (6-24 hours) presenters. We performed semiautomated segmentations of the acute ischemic lesion on NCCT using 5% relative density difference () and used the relative cerebral blood flow <30% to segment the CTP core. On coregistered images, we performed volumetric and voxel-based analyses to compare infarct estimations by imaging modality. Spatial accuracy for the follow-up infarct was assessed using the Dice similarity coefficient (DSC) and balanced accuracy.

Results: We included 109 patients with a median age of 70 (interquartile range [IQR] 31-93) years of whom 52% were female. The follow-up infarct was underestimated by the CTP core (mean absolute volume difference [MAVD] = 14 mL [SD 36], < 0.001), but not by the union lesion (MAVD = 3 mL [SD 32], = 0.76). Infarct underestimation was greater in late presenters (median 17 mL [IQR 7-33] vs 7 mL [IQR 4-25] in early presenters, < 0.01) and in patients with poor collaterals (median 20 mL [IQR 8-56] vs 8 mL [IQR 4-20] in patients with good collaterals, < 0.01). Median 25% of the infarct missed by the CTP core could be detected on baseline rNCCT in late presenters (vs. median 3% in early presenters). The combined and CTP core lesion more accurately detected the follow-up infarct compared with the CTP core alone (median DSC 0.37 [IQR 0.06-0.55] vs 0.18 [IQR 0-0.42] and median balanced accuracy 0.67 [IQR 0.53-0.75] vs 0.56 [IQR 0.50-0.67], < 0.001 for both).

Discussion: Underestimation of follow-up infarct by CTP is substantial and the follow-up infarct can partially be detected by baseline NCCT, especially in patients with stroke with delayed presentation. Combining and CTP increases the accuracy for predicting the follow-up infarct.