Arjen Lindenholz

111 Intracranial Atherosclerosis Assessed with 7T MRI 5 Introduction Intracranial atherosclerosis (ICAS) is an important cause of ischemic stroke, 1 especially in black, Hispanic, and Asian populations, where ICAS accounts for up to 50%of all ischemic stroke or transient ischemic attacks (TIA). 1-4 Inwhite populations, ICAS accounts for 5%-23% of ischemic strokes. 2,5,6 ICAS has been associated with many of the risk factors for atherosclerotic disease, including hypertension, hyperlipidemia, diabetes mellitus, and smoking. 2-4,7-10 However, those studies used lumenographic techniques (e.g., CT angiography, MR angiography, or intra-arterial digital subtraction angiography) to assess intracranial calcifications or stenosis as a proxy for ICAS. 3-5,7,8 Although these methods enable the accurate assessment of luminal narrowing, they are limited in assessing the vessel wall itself. 11,12 Because of arterial remodeling, ICAS results in luminal narrowing only at a more advanced stage of the disease. 13,14 Therefore, subtle atherosclerotic plaques or other nonstenotic intracranial vessel wall lesions are easily missed with these lumenographic techniques. With high-field (3 tesla (T) and 7T) intracranial MRI, both stenotic and nonstenotic vessel wall lesions can be detected. 15-18 Specifically developed intracranial vessel wall sequences have therefore been increasingly used to evaluate intracranial atherosclerotic disease, including the characterization of vessel wall lesions and possible contrast enhancement of the vessel wall. 15,19 For the first time, to our knowledge, a recent American study used intracranial vessel wall MRI at 3T to assess the relationship between vascular risk factors and intracranial atherosclerosis. 20 However, this study was performed in a community-based cohort and its main focus was on the role of ethnicity – not TIA or stroke – on ICAS prevalence. We hypothesize that increasing age, hypertension, male sex and hyperlipidemia increase the vessel wall lesion burden in Caucasian participants with an ischemic stroke or TIA. In our study, we investigated the relation between vascular risk factors and intracranial vessel wall lesion burden using intracranial vessel wall MRI at 7T in participants with ischemic stroke or TIA.