Relation Of Imaging Outcomes Of CTA Collaterals Grades To Penumbra Assessed By CTP In Acute Ischemic Stroke

Purpose: The purpose was to explore the relationship between computed tomography angiography(CTA)–derived collateral status and computed tomography perfusion(CTP)–derived tissue viability.Methods: We followed the following inclusion criteria to collect patients: a)time from witnessed symptom onset to first CT scan < 12 hours;b)middle cerebral artery(MCA)M1 / M2 segment and/or internal carotid artery(ICA)occlusion;c)CTP suggested the presence of ischemic hypo-perfusion.Collateral perfusion was graded from 0(no visible collaterals)to 3(complete collateral supply)on maximum intensity projection(MIP)images of CTA.We investigated the area with relative cerebral blood flow(r CBF)<30% or time-to-maximum(Tmax)>10s,>12s or >14 s as infarct core,and Tmax >6s as hypoperfused deficit.Penumbra was defined as hypoperfusion deficit minus infarct core and mismatch ratio was defined as the rate of the area of penumbra to infarct core.Kruskal–Wallis and Spearman correlation tests were performed to assess the correlation between collateral grades and infarct size or mismatch ratio.Results: 106 patients were enrolled in this study and 75 of them met imaging and clinical criteria.Collaterals were scored 0 in 9 patients,1 in 28 patients,2 in 21 patients,3 in 17 patients.Infarct sizes defined by r CBF <30% or Tmax >10s,>12s or >14s and mismatch ratios were significantly different among four groups(P<0.01).There was no significant difference in age and time from symptom to CT among the patient groups of the four grades(p=0.540 for age and p=0.359 for time).The correlation between collateral grades and infarct core using r CBF <30%(r=-0.785,P<0.01)was better than that defined by Tmax >10s,>12s or >14s.Mismatch ratio for the infarct core defined by r CBF <30%(r=0.897,P<0.01)had the best correlation with collateral grades.The three thresholds of Tmax were compared with each other and we found that Tmax>14s was most closely related to collateral circulation(r=-0.66,P<0.01 for infarct size;r=0.706,P<0.01 for mismatch ratio).The NIHSS score was negatively correlated with collateral grade(r=-0.643,P<0.01).Conclusion:(1)CTA and CTP have good correlation in reflecting collateral circulation;(2)Patients with good collaterals show a smaller infarct core and higher mismatch ratio;(3)Infarct size defined by r CBF <30% and mismatch ratio defined by r CBF <30% and Tmax >6s appear to be more correlated with collateral grades in acute ischemic stroke patients.