Abstract
Objective CT-perfusion (CTP) has revolutionised stroke care by improving diagnostic accuracy and expanding eligibility to acute therapies. Software packages utilise various mathematical techniques to transform raw perfusion data into measures of infarct core and ischaemic penumbra. These techniques have been derived from studies of anterior-circulation stroke and not yet validated in posterior circulation stroke (PCS). We examined the optimal CTP thresholds for acute PCS.
Methods Data were analysed from 331-patients diagnosed with a PCS enrolled in the International-stroke-perfusion-registry (INSPIRE). Twenty-seven-patients with baseline multimodal-CT with occlusion of a large posterior-circulation (PC) artery and follow up diffusion-weighted-MRI at 24–48 hours were included. CTP parametric maps were generated using five different post-processing methods. Receiver operating curve (ROC) analysis and linear regression were used for voxel-based analysis and volume-based analysis respectively. Optimality was defined as the postprocessing method which maximised the area-under-the-curve and resulted in the smallest mean-volume-difference between the acute perfusion lesion and follow-up MRI.
Results Partial-deconvolution was the optimal post-processing method for characterisation of ischaemic-penumbra and infarct-core. Mean-transit-time (MTT) at a threshold of >165% and >195% most accurately defined ischaemic-core (AUC=0.73) and penumbra (AUC=0.78). Post-processing technique influenced accuracy of core (AUC range=0.54–0.73) and penumbra (AUC range=0.72–0.79) estimates. MTT was consistently the most accurate parameter at distinguishing core and penumbra across all post-processing methods.
Conclusion CTP has significant diagnostic utility in PCS. Accuracy of CTP varies considerably by post-processing method. The underlying post-processing technique employed by individual software packages should be considered when interpreting the accuracy of ischemic core and penumbra estimates.
