Cerebral blood flow is the best CT perfusion predictor of infarct core in ischemic stroke

  • Dr Bruce Campbell, Royal Melbourne Hospital, University of Melbourne, Australia
  • Dr Soren Christensen, Royal Melbourne Hospital, University of Melbourne, Australia
  • Prof Christopher Levi, John Hunter Hospital and Hunter Medical Research Institute, University of Newcastle, Australia
  • Prof Patricia Desmond, Royal Melbourne Hospital, University of Melbourne, Australia
  • Prof Geoffrey Donnan, Florey Neuroscience Institutes, University of Melbourne, Australia
  • Prof Stephen Davis, Royal Melbourne Hospital, University of Melbourne, Australia
  • A/Prof Mark Parsons, John Hunter Hospital and Hunter Medical Research Institute, University of Newcastle, Australia

Objective: CT perfusion (CTP is widely and rapidly available for imaging acute ischemic stroke but has limited validation. Cerebral blood volume (CBV) has been proposed as the best predictor of infarct core. We tested CBV against other common CTP parameters using contemporaneous diffusion MRI.
Methods: Acute ischemic stroke patients <6hr after onset had CTP and diffusion MRI within 1hr, before any reperfusion therapies. CTP maps of time to peak (relTTP), absolute and relative CBV, cerebral blood flow (CBF), mean transit time (MTT) and time to peak of the deconvolved tissue residue function (Tmax) were generated. The diffusion lesion was manually outlined to its maximal visual extent. Receiver operating characteristic (ROC) analysis area-under-the-curve (AUC) was used to quantify performance of each perfusion parameter in predicting the concurrent DWI lesion. Optimal thresholds were determined (Youden's index).
Results: In analysis of 98 CTP slabs (54 patients, median onset to CT 190min, median CT to MR 30min), relative CBF performed best (AUC 0.79, 95%CI 0.77-81), significantly better than absolute CBV (AUC 0.74, 95%CI 0.73-0.76). The optimal threshold was <31% of mean contralateral CBF. Specificity was limited by undetectable CBF/CBV in normal white matter in cases with reduced contrast bolus intensity and leukoaraiosis.
Conclusions: In contrast to previous reports, CBF predicted the acute DWI lesion significantly better than CBV. However, no simple threshold avoids detection of significant false positive regions in normal white matter. This relates to low signal to noise ratio in CTP maps and emphasizes the need for optimized acquisition and post-processing.