Perfusion Computed Tomography Accurately Quantifies Collateral Flow After Acute Ischemic Stroke

Background and Purpose— This study aimed to derive and validate an optimal collateral measurement on computed tomographic perfusion imaging for patients with acute ischemic stroke. Methods— In step 1 analysis of 22 patients, the parasagittal region of the ischemic hemisphere was divided into 6 pial arterial zones to derive the optimal collateral threshold by receiver operating characteristic analysis. The collateral threshold was then used to define the collateral index in step 2. In step 2 analysis of 156 patients, the computed tomographic perfusion collateral index was compared with collateral scores on dynamic computed tomographic angiography in predicting good clinical outcome by simple regression. Results— The optimal collateral threshold was delay time >6 s (sensitivity, 88%; specificity, 92%). The computed tomographic perfusion collateral index, defined by the ratio of delay time >6 s/delay time >2 s volume, showed a significant correlation with dynamic computed tomographic angiography collateral scores (correlation coefficient, 0.62; P P Conclusions— Computed tomographic perfusion can accurately quantify collateral flow after acute ischemic stroke.