Objective:To observe the diagnostic threshold values of predicting delayed cerebral ischemia(DCI)after subarachnoid hemorrhage(SAH)with computed tomography perfusion(CTP). Methods:Totally 122 patients with SAH were respectively enrolled.CT perfusion values

including cerebral blood flow(CBF)

cerebral blood volume(CBV)

mean transit time(MTT)

and time to peak(TTP)in predefined regions of interest were measured. All patients were divided into DCI group and non-DCI group. Diagnostic threshold values for DCI were evaluated and sensitivity and specificity were calculated for optimal thresholds. Results:Of 122 patients with SAH

43 had DCI

79 didn’t have DCI. The CBF was lower

MTT and TTP was longer and perfusion asymmetry was lager in DCI group than in non-DCI group(P<0.05). The areas under ROC curves of CBF

CBV

CBF ratio

CBV ratio

MTT

TTP

MTT difference

TTP difference were 0.87

0.69

0.81

0.76

0.88

0.72

0.71

0.78;the optimal threshold values were 15.91ml/(min·ml)

1.76 ml/100 g

0.84

0.83

9.65

11.46

0.68

0.48 s. MTT

CBF

CBF ratio had high diagnostic value in predicting DCI and the sensitivity and specificity were MTT of 69.77% and 93.67%

CBF of 72.10% and 88.60% and CBF of 69.77% and 91.14%. Conclusion:The cerebral microcirculation hemodynamic after SAH can be evaluated by CTP. CT perfusion is an early and reliable predictor of DCI.