Identification of penumbra and infarct in acute ischemic stroke using computed tomography perfusion-derived blood flow and blood volume measurements

Background and Purpose-We investigated whether computed tomography (CT) perfusion-derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients. Methods-Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (n = 16) and those without (n = 9). Penumbra was operationally defined as tissue with an admission CBF < 25 mL . 100 g(-1) . mint that was not infarcted on the 5- to 7-day NCCT. Logistic regression was applied to differentiate between infarct and penumbra data points. Results-For recanalized patients, CBF was significantly lower (P < 0.05) for infarct (13.3 +/- 3.75 mL . 100 g(-1) . min(-1)) than penumbra (25.0 +/- 3.82 mL . 100 g(-1) . min(-1)). CBV in the penumbra (2.15 +/- 0.43 mL . 100 g(-1)) was significantly higher than contralateral (1.78 +/- 0.30 mL . 100 g(-1)) and infarcted tissue (1.12 +/- 0.37 mL . 100 g(-1)). Loggistic regression using an interaction term (CBF x CBV) resulted in sensitivity, specificity, and accuracy of 97.0%, 97.2%, and 97.1%, respectively. The interaction term resulted in a significantly better (P < 0.05) fit than CBF or CBV alone. suggesting that the CBV threshold for infarction varies with CBF. For patients without recanalization, CBF and CBV for infarcted regions were 15.1 +/- 5.67 mL . 100 g(-1) . min(-1) and 1.17 +/- 0.41 mL . 100 g(-1), respectively. Conclusions-We have shown in a limited sample of patients that CBF and CBV obtained from CTP can be sensitive and specific for infarction and should be investigated further in a prospective trial to assess their utility for differentiating between infarct and penumbra.