Ischemic Core Overestimation on Computed Tomography Perfusion

Abstract

Background and Purpose: Different studies have pointed that CT perfusion (CTP) could overestimate ischemic core in early time window. We aim to evaluate the influence of time and collateral status on ischemic core overestimation. Methods: Retrospective single-center study including patients with anterior circulation large-vessel stroke that achieved reperfusion after endovascular treatment. Ischemic core and collateral status were automatically estimated on baseline CTP using commercially available software. CTP-derived core was considered as tissue with a relative reduction of cerebral blood flow <30%, as compared with contralateral hemisphere. Collateral status was assessed using the hypoperfusion intensity ratio (defined by the proportion of the time to maximum of tissue residue function >6 seconds with time to maximum of tissue residue function >10 seconds). Final infarct volume was measured on 24 to 48 hours noncontrast CT. Ischemic core overestimation was considered when CTP-derived core was larger than final infarct. Results: Four hundred and seven patients were included in the analysis. Median CTP-derived core and final infarct volume were 7 mL (interquartile range, 0–27) and 20 mL (interquartile range, 5–55), respectively. Median hypoperfusion intensity ratio was 0.46 (interquartile range, 0.23–0.59). Eighty-three patients (20%) presented ischemic core overestimation (median overestimation, 12 mL [interquartile range, 41–5]). Multivariable logistic regression analysis adjusted by CTP-derived core and confounding variables showed that poor collateral status (per 0.1 hypoperfusion intensity ratio increase; adjusted odds ratio, 1.41 [95% CI, 1.20–1.65]) and earlier onset to imaging time (per 60 minutes earlier; adjusted odds ratio, 1.14 [CI, 1.04–1.25]) were independently associated with core overestimation. No significant association was found with imaging to reperfusion time (per 30 minutes earlier; adjusted odds ratio, 1.17 [CI, 0.96–1.44]). Poor collateral status influence on core overestimation differed according to onset to imaging time, with a stronger size of effect on early imaging patients( P interaction <0.01). Conclusions: In patients with large-vessel stroke that achieve reperfusion after endovascular therapy, poor collateral status might induce higher rates of ischemic core overestimation on CTP, especially in patients in earlier window time. CTP reflects a hemodynamic state rather than tissue fate; collateral status and onset to imaging time are important factors to consider when estimating core on CTP.

Stroke imaging prior to thrombectomy in the late window: results from a pooled multicentre analysis

“…Our report and other studies show that a favourable collateral profile is often concordant with that of perfusion. Moreover, there is evidence to suggest that perfusion imaging can overestimate the extent of irreversibly damaged brain tissue 31. Results from ongoing randomised trials that select late-window patients for EVT versus medical treatment using CT/CTA may provide further evidence on this issue.…”

Accuracy of CT Perfusion–Based Core Estimation of Follow-up Infarction

“…Our results are compatible with prior studies that suggested that ischemic core thresholds may be time-dependent [22][23][24] and stricter core thresholds should be used for patients who received perfusion imaging very early after symptom onset. 25 Ischemic core overestimation is a potential concern that has been controversial in the stroke community, with recent articles 14,21,26 suggesting that patients may be excluded from receiving EVT based on CTP overestimation of irreversible injury. The purpose of this study was to evaluate whether infarct core overestimation is frequent with the currently established rCBF <30% threshold, the effect of time from LKW and time from imaging to successful reperfusion on the incidence of potential overestimation, and whether the core overestimation can be eliminated with a more stringent rCBF <20% threshold.…”

“…Significant underestimation of infarct volume was defined as the follow-up infarct volume being at least 25 mL larger than estimated ischemic core volume on baseline CTP, 19,20 whereas core overestimation was defined as ischemic core volume at baseline being ≥10 mL larger than infarct volume on follow-up DWI. 14,21 The rest were defined as adequate estimation (core corresponding to DWI infarct).…”

Predictors of Early Neurological Improvement in Patients with Anterior Large Vessel Occlusion and Successful Reperfusion Following Endovascular Thrombectomy—Does CT Perfusion Imaging Matter?

“…The different definition of study endpoints (ENI versus mRS at day 90) might be one explanation. Another reason might be ischemic core overestimation on CTP, particularly in patients in earlier time windows and those with rapid reperfusion [33][34][35]. Due to potential presence of ghost infarct core on CTP, caution must be applied in decision-making for endovascular therapy in patients presenting with early time window within 3 h [36].…”