Whole-brain CT perfusion measurement of perfused cerebral blood volume in acute ischemic stroke: probability curve for regional infarction

PURPOSE: To determine the probability curve for regional cerebral infarction as a function of percentage normalized perfused cerebral blood volume (pCBV) in patients with acute ischemic stroke. MATERIALS AND METHODS: The authors retrospectively analyzed whole-brain computed tomographic (CT) perfusion scans from 28 patients with acute stroke (<6 hours) due to major arterial occlusion, without intracranial hemorrhage. Each patient had a positive follow-up CT scan 1-4 days later, without interval thrombolysis. Normalized pCBV, expressed as a percentage of contralateral normal brain pCBV, was determined in the core infarction and in regions just inside and outside the boundary between infarcted and noninfarcted brain. These regions were dichotomized into infarcted (core and inner band) and noninfarcted (outer band) categories. Logistic regression analysis was then used to create a reference curve of probability of infarction as a function of percentage normalized pCBV. RESULTS: Normalized pCBV values in the core, inner band, and outer band were 24.5% +/- 2.3, 36.3% +/- 2.4, and 72.1% +/- 2.4, with corresponding probabilities of infarction of .99, .96, and .11. The normalized pCBV at which the probability of survival reached .5 was 58.0% +/- 0.5. Sensitivity, specificity, and accuracy of the reference probability curve were 90.5% (209 of 231), 89.5% (212 of 237), and 90.0% (421 of 468), respectively. Negative and positive predictive values were 90.6% (212 of 234) and 89.3% (209 of 234), respectively. R2 was 0.73, and differences in perfusion between core and inner and outer bands were highly significant (P <.0001). CONCLUSION: A probability of infarction curve can help predict the likelihood of infarction as a function of percentage normalized pCBV.