[Thresholds of CT perfusion in predicting ischemic penumbra and infarct core in patients with acute ischemic stroke]

To determine the optimal parameters and their thresholds on CT perfusion (CTP) to predict the penumbra and core in patients with acute ischemic stroke.

The data of 39 thrombolytic candidates with acute cerebral anterior-circulation ischemic stroke admitted in the Second Affiliated Hospital, Zhejiang University School of Medicine from June 2009 to October 2013 were retrospectively reviewed. Patients all underwent CTP at admission and CTP or magnetic resonance perfusion (MRP) 24 h after thrombolysis. Patients were classified as non-reperfusion group (to define the threshold of penumbra, n=10) and reperfusion group (to define the threshold of infarct core, n=21) by reperfusion status. According to the baseline CTP and 24 h imaging, the volumes of threshold-based hypoperfusion lesions and final infarction were calculated. Paired t test, correlation analysis and Bland-Altman plot were performed to assess the optimal thresholds for predicting the penumbra and infarct core.

In non-reperfusion group, the best agreement was found between final infarct volume and delay time>3 s (bias 3.3 ml, 95% limits of agreement:-41.7 to 48.3 ml, r=0.933, P<0.001), while in reperfusion group, the best agreement was noted between final infarct volume and rCBF<30% (bias -2.2 ml, 95% limits of agreement:-25.6 to 21.2 ml; r=0.923, P<0.001).

Delay time>3 s and rCBF<30% are the optimal thresholds for predicting the penumbra and infarct core on CTP, respectively. These thresholds may be of help to estimate the mismatch status and select eligible patients for thrombolysis.