Abstract P318: Ischemic Core Overestimation on Computed Tomography Perfusion

Abstract

Introduction: 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 available software. CTP-derived core was considered as tissue with a relative reduction of cerebral blood flow <30%. Collateral status was assessed using the hypoperfusion intensity ratio(defined by the proportion of the Tmax>6 seconds with Tmax>10 seconds, HIR). Final infarct was measured on 24-48 hours non-contrast 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 were 7mL(IQR 0-27) and 20mL(IQR 5-55), respectively. Median HIR was 0.46(IQR 0.23-0.59). 83 patients(21%) presented ischemic core overestimation(median overestimation, 12mL(IQR 5-41)). Multivariable logistic regression analysis adjusted by CTP-derived core and confounding variables showed that poor collateral status (per 0.1 HIR increase, adjusted odds ratio(aOR) 1.41, 95% confidence interval(CI)1.20-1.65) and earlier onset to imaging time(per 60 minutes earlier, aOR 1.14, CI1.04-1.25) were independently associated with ischemic core overestimation. No significant association was found with imaging to reperfusion time(per 30 minutes earlier, aOR 1.17 CI0.96-1.44). Poor collateral status influence on ischemic core overestimation differed according to onset to imaging time, with a stronger size of effect on early imaging patients(pinteraction<0.01). Conclusion: 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 estimate ischemic core on CTP.