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

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). 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 (rNCCT>5%) 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. 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], p < 0.001), but not by the union lesion (MAVD = 3 mL [SD 32], p = 0.76). Infarct underestimation was greater in late presenters (median 17 mL [IQR 7-33] vs 7 mL [IQR 4-25] in early presenters, p < 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, p < 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 rNCCT>5% 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], p < 0.001 for both). 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 rNCCT>5% and CTP increases the accuracy for predicting the follow-up infarct.