Intracranial Calcification Burden Is An Imaging Marker For Hemorrhagic Transformation And Prognosis In Ischemic Strokes Treated With Thrombolysis

Background and objective: Calcification is a major part of atherosclerosis,not only in brain vessels,but also in coronary arteries and peripheral arteries.Usually,identification of calcification indicates higher atherosclerosis burden and impaired cerebral function.Intravenous thrombolysis as an effective revascularization approach for acute ischemic stroke patients could reduce disability and death significantly,while there is still a 3 percent of hemorrhage transformation,also some patients eventually turned out to have poor prognosis.Non-contrast CT is a routine imaging protocol in neurology emergency room,also a routine test for patients going to undertake intravenous thrombolysis.We aim to identify and quantify calcification in seven main vessels(bilateral internal carotid arteries,bilateral middle cerebral arteries,bilateral vertebral arteries and basilar artery),also explore the correlation between calcification burden and hemorrhage transformation and prognosis.Methods: Patients diagnosed of acute ischemic stroke in anterior circulation that underwent intravenous thrombolysis therapy in the First Hospital of Jilin University from July 2015 to June 2017 were retrospectively consecutively included.All the included patients underwent baseline CT before thrombolysis as well as follow-up CT at 24-hour after thrombolysis,along with thorough clinical information and prognosis evaluation.Imaging analysis was completed respectively by two neuroimaging specialists,blinded with all the clinical information.A third-party software ITK-SNAP was used for segmentation and measurement of calcification.The threshold for calcification was if CT value higher than 130 HU.The calcification volume on lesion side and the overall calcification volume were grouped by quartile for analysis.The criterion for hemorrhage transformation was the same as ECASS ?.The criterion for poor prognosis was if m RS scoring higher than 2 on three months.Statistical analysis was undertaken by SPSS 22.0(SPSS,IBM,West Grove,PA,USA).The significance for P value was 0.05.Measurement data was shown by average value ± standard derivation or median with quartile.Enumeration data was shown by percentage.Comparison of two sets of measurement data was done by t-test or Mann-Whitney test according the normality test.Comparison of two sets of enumeration data was done by chi-square test,calibration of chi square test or Fisher exact probability.Correlation analysis between outcome variable and influence factors was undertaken by logistic regression analysis,as well as sensitivity analysis.Results: 176 patients were included,among which 155 patients were identified of calcification in seven main vessels.Univariable analysis inferred that baseline NIHSS of calcification group was higher than that of non-calcification group(P<0.05).27 patients were identified of hemorrhage transformation,univariable analysis found that baseline NIHSS of HT group was higher than that of non-HT group(P<0.05),and the number of calcified vessels,calcification volume of lesion side,overall calcification volume,grouping of calcification volume on lesion side and grouping of overall calcification volume were all higher than that of non-HT group.In sensitivity analysis,grouping of calcification volume on lesion side showed statistical difference in all four models,with OR value fluctuated from 1.65 to 1.76.Among included 176 patients,70 were identified of poor prognosis.Univariable analysis found that baseline NIHSS of poor prognosis group was higher than that of good prognosis group.Identification of calcification in seven main vessels and number of calcified vessels in poor prognosis group were higher than that of good prognosis group.Sensitivity analysis found that number of calcified vessels showed statistical difference in all four models(P<0.05),with OR value fluctuated from 1.50-1.54.Conclusions: Acute ischemic stroke patients with intracranial calcification tend to have severer neurological impairment than non-calcification patients.Grouping of calcification volume on lesion side could independently predict hemorrhage transformation after intravenous thrombolysis.Number of calcified vessels could independently predict poor prognosis on three months.