Quantitative evaluation of intracranial artery calcification on brain unenhanced CT and its clinical implications

Ph.D. ; Intracranial arterial calcification (IAC) is an easily identifiable entity on unenhanced brain computed tomography (CT) scans. Recent findings from Caucasians demonstrated the associations between carotid artery calcification and ischemic stroke. Our previous studies found a higher prevalence of IAC in Chinese populations. However, its clinical implications in Asian and underlying mechanisms are still unknown. In this thesis, we aimed to validate different IAC measuring methods, investigate clinical implications of IAC, and delineate related hemodynamic effects. ; An objective method for IAC assessment using consistent criteria is urgently required for comparison among multiple studies. We first assessed the reliability of Agatston method (contains information of both intensity and volume of calcium) in IAC measurement by comparing it with volumetric or qualitative methods. Our findings suggested that IAC Agatston score is highly reproducible, and might be a potential target for future research. ; Secondly, we tried to verify the predictive values of IAC on vascular events in Chinese adults. In a hospital-based cohort study, we recruited 407 consecutive patients who were referred for brain CT imaging in our hospital during December 2004 and January 2005. Patients were followed up till 2016 (median follow-up duration 8.1 years). IAC Agatston score was found independently predictive of non-cardioembolic stroke (HR 1.747), myocardial infarction (HR 3.195), and cardiovascular death (HR 1.632). Another study prospectively recruited 694 consecutive acute ischemic stroke patients from a population-based stroke registry, and followed up till 2016 (median duration 8.8 years). IAC Agatston score was found an independent predictor for both recurrent stroke (HR 1.301) and stroke death (HR 1.441). The results of this part suggested that IAC Agatston score is of great values in predicting vascular events, including non-cardioembolic stroke, myocardial infarction, recurrent stroke, cardiovascular death, and stroke ...