It has been acknowledged that delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) can be diagnosed by CT perfusion (CTP) in the DCI time-window. We evaluated the diagnostic accuracy of CTP for DCI during the early stage of the time-window.

We prospectively enrolled patients with aneurysmal SAH. DCI was defined as both new cerebral infarction and clinical deterioration after SAH. CTP was performed by using a standardized protocol with predefined regions of interest in 4 to 6 days after SAH. We quantitatively evaluated the diagnostic accuracy of eight CTP parameters (4 for absolute parameters and 4 for relative parameters). The receiver operator characteristic (ROC) curves of all parameters were generated and the optimal threshold values were derived for the calculation of sensitivities and specificities.

Fifty-three patients were enrolled and 20 patients were diagnosed with DCI. In the analysis of absolute CTP parameters, CBF and MTT had areas under the curve (AUC) >0.75 and the optimal threshold value was 40.4mL/100g/min and 3.78seconds, respectively. Through the evaluation of relative CTP parameters, all 4 parameters had AUC >0.75 and the optimal threshold value was 0.9 for CBV ratio, 0.85 for CBF ratio, 0.32seconds for MTT difference and 1.31seconds for TTP difference.

Besides two absolute CTP parameters (CBV and TTP), all six CTP parameters can be used as good diagnostic tests for DCI in the early stage of the time-window.