Cerebral Blood Flow Is the Optimal CT Perfusion Parameter for Assessing Infarct Core

Abstract

Background and Purpose-CT perfusion (CTP) is widely and rapidly accessible 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-Patients with acute ischemic stroke Ͻ6 hours after onset had CTP and diffusion MRI Ͻ1 hour apart, before any reperfusion therapies. CTP maps of time to peak (TTP), 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 the correspondence of each perfusion parameter to the coregistered diffusion-weighted imaging lesion. Optimal thresholds were determined (Youden index). Results-In analysis of 98 CTP slabs (54 patients, median onset to CT 190 minutes, median CT to MR 30 minutes), 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 Ͻ31% of mean contralateral CBF. Specificity was reduced by low CBF/CBV in noninfarcted white matter in cases with reduced contrast bolus intensity and leukoaraiosis. Conclusions-In contrast to previous reports, CBF corresponded with the acute diffusion-weighted imaging lesion better than CBV, although no single threshold avoids detection of false-positive regions in unaffected white matter. This relates to low signal-to-noise ratio in CTP maps and emphasizes the need for optimized acquisition and postprocessing. (Stroke. 2011;42:3435-3440.)

Toward Patient-Tailored Perfusion Thresholds for Prediction of Stroke Outcome

“…Among studied parameters, CBF best predicted final infarct consistent with other studies. 19,20 The reduced performance of CBV for infarct determination in the present study is consistent with prior studies. 20 This result is intuitive if we consider that CBV reduction may represent already infarcted tissue with minimal prospects for improvement irrespective of other clinical factors such as collaterals and rtPA treatment.…”

CTA Collateral Status and Response to Recanalization in Patients with Acute Ischemic Stroke

“…Collateral status by use of the rLMC score (0 -20) was trichotomized into 3 groups: good (17)(18)(19)(20), intermediate (11)(12)(13)(14)(15)(16), and poor (0 -10), according to previously published literature. 3 Differences between these 3 groups were assessed by means of the Fisher exact test for proportions, 1-way ANOVA for parametric data, and a rank sum test for nonparametric data.…”

Performance and Predictive Value of a User-Independent Platform for CT Perfusion Analysis: Threshold-Derived Automated Systems Outperform Examiner-Driven Approaches in Outcome Prediction of Acute Ischemic Stroke

“…18 Both CBV and CBF have been proposed as estimates of irreversibly infarcted (core) tissues, with past investigations describing both absolute and relative (rCBV, rCBF) thresholds for the detection of infarct core. 19 For the purposes of this study, separate estimates were supplied for each, thresholded at relative rCBF or rCBV Ͻ30% normal. Color-coded core maps for both parameters were automatically generated and overlaid on source images for review purposes (Fig 2).…”