| Background: With the publication of multiple positive trials,mechanical thrombectomy(MT)has made considerable progress in treating acute stroke due to large vessel occlusion.Hyper-densities can frequently be observed on CT immediately after MT,and it is sometimes difficult to differentiate between contrast and the early hemorrhagic transformation(HT).HT is recognized as a serious complication of reperfusion that increases disability and mortality.It is difficult for physicians to reach an agreement on the nature of hyper-densities,which may affect patients’ subsequent treatments,and even prognosis.Both and MRI and dual energy CT may be substitutes for normal CT on that situation,especially the latter,which provides better images and shows advantages in material separation supposedly.Purpose: To evaluate the efficacy of dual energy CT in identifying hyper-densities among patients following undergoing MT.Methods: Data of patients with acute ischemic stroke in the Taizhou People’s hospital from January 2018 to August 2020,were reviewed retrospectively.Eligible patients should have a post-procedural third-generation dual-source CT scan of brain within 4 hours,and a follow-up scan about 24 hours after the operation.Alberta Stroke Program Early CT Score(ASPECTS)regions were recorded on the original linearly weightedaverage mixtures(MIX)images(of which coefficient is 0.5),where the patients with hyper-densities(or delayed HT)existed.The CT scores were independently measured by two radiologists,and the means of the two were used.Another radiologist used virtual non-contrast(VNC)images and iodine overlay maps(IOM)to identify hyperdensities,and finally confirmed its nature on follow-up images(18-36 h after the reperfusion): the hyper-densities which are present in then will be deemed as HT.This study defined delayed HT as the HT that was not originally displayed on the MIX,but was visible on the follow-up images,or the original hematoma expended to other ASPECTS regions.Results: A total of 50 patients with anterior circulation large vessel occlusion who underwent MT were included,including 16 females and 34 males.The average age of them was 67.5 ±12.7.The median of the National Institutes of Health Stroke Scale(NIHSS)at the time of admission was 13(11-17).Forty-three patients showed hyperdensities in 171 corresponding ASPECTS regions after MT.All the regions that were initially identified as contrast were confirmed,and HT were detected in 25 regions on VNC and IOM,while only 9 regions were mistaken as contrast.Besides,delayed HT were observed in 12 regions.When distinguishing between contrast and HT based on VNC image and IOM,the sensitivity was 73.5%,the specificity was 100%,the positive predictive value was 100%,the negative predictive value was 93.8%,and the accuracy rate was 94.7% respectively.The values measured by the two radiologists were roughly the same(70.9±27.2 v.s.70.9±27.2),and the difference was not statistically significant(P=0.57).The cut-off index of the attenuation value for differentiating hemorrhage on VNC images,which was calculated by receiver operating characteristic(ROC)curve analysis,was 71.35 HU(P<0.05,AUC=0.792),showing a sensitivity of 92.6% and a specificity of 67.9%.While the attenuation value used to distinguish non-delayed HT was 56.00 HU(P<0.05,AUC=0.995),which is invalid in practice and contrary to its definition.Thus,dual energy CT failed to predict the occurrence of delayed HT.According to Heidelberg Bleeding Classification,10 patients experiencing symptomatic intercranial hemorrhage and another two with separate subarachnoid hemorrhage were also found in this study.Conclusion: Higher diagnostic accuracy could be obtained only by VNC image and IOM,when the third-generation dual-energy CT is used to identify hyper-densities.On the MIX,71.35 HU is the predict threshold with acceptable specificity and sensitivity to differentiate between contrast and the early HT. |
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