Serial low-dose quantitative CT perfusion for the evaluation of delayed cerebral ischaemia following aneurysmal subarachnoid haemorrhage

To investigate the appropriate time and computed tomography perfusion (CTP) parameters for predicting delayed cerebral ischaemia (DCI) following aneurysmal subarachnoid haemorrhage (aSAH).All patients underwent baseline CTP within 24 hours and follow-up CTP on day 4 and day 7 after aSAH. The quantitative and semi-quantitative parameters, cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), time to peak (TTP), relative CBV and CBF (rCBV, rCBF), and MTT and TTP difference (ΔMTT, ΔTTP) were compared between the DCI and non-DCI (NDCI) groups at the three time points.Thirty-nine patients were included. Twelve patients developed DCI. CBF, rCBF, and ΔMTT were significantly different in the DCI group among all time points (p0.05), but these parameters did not significantly change from day 4 to day 7. CBF and rCBF in the DCI group were lower than in the NDCI group. ΔMTT in the DCI group was longer than in the NDCI group, but significant differences were only found in the two follow-up CTPs (both p0.05). The optimal threshold values distinguishing DCI and NDCI were 40.1 ml/100 g/min for CBF, 0.90 for rCBF and 0.33 seconds for ΔMTT. The follow-up CTP on day 4 was an appropriate time to predict DCI after aSAH.The follow-up CTP on day 4 after aSAH can be helpful for the early identification of DCI. CBF, rCBF, and ΔMTT were found to be the best prognosticators for the development of DCI.