Dynamic contrast enhancement and wall enhancement index for the quantitative assessment of vascular wall abnormalities in intracranial atherosclerosis: a pilot study

Background: Breakthrough neurotechnologies have allowed for new understanding of some brain disorders; however, identification and differential diagnosis of intracranial stenotic and occlusive lesions remains challenging. Magnetic resonance imaging (MRI) with dynamic contrast enhancement (DCE) is a tool that could be used for the quantitative assessment of endothelial permeability and microvascular volume in atherosclerotic plaques (AP). Aim: To assess quantitative parameters of vascular wall abnormalities in AP area and in obviously unchanged wall of intracranial arteries with MRI DCE and high spatial resolution Т1-weighed images before and after contrast injection, with calculation of the wall enhancement index (WEI) by mathematical modelling. Methods: This was a pilot cross-sectional uncontrolled study with consecutive recruitment of 29 patients with atherosclerotic abnormalities of brachiocephalic arteries, including intracranial. The patients’ median age was 66 [57; 72] years; they were mostly men (75.9%, n = 22). For the assessment of any brain abnormalities, MRI (magnetic induction 3 Tesla, Magnetom Prisma, Siemens) was performed in patients with standard sequence (Т2, T2-FLAIR), as well as MRI DCE for the assessment of intracranial arteries, before and after intravenous contrast injection, with high spatial resolution T1-weighed imaging and suppression of the signal from bloodstream and fat, with the calculation of WEI. Results: There were significant differences in WEI in AP and in unchanged wall (0.962 [0.686; 1.387] vs. 0.111 [0.014; 0.206], p 0.001). No significant differences were found between WEI values in internal carotid arteries APs (0.722 [0.573; 1.580]), middle cerebral arteries (0.921 [0.725; 1.183]), and basilar artery (1.343 [1.002; 1.419]) (p = 0.381). We also found significant difference (p = 0.034) in the extravascular extracellular fraction volumes ve (Tofts) in AP located in the basilar artery (0.171 [0.146; 0.325]), internal carotid arteries (0.579 [0.358; 1.000]), and middle cerebral arteries (0.134 [0.101; 0.269]). Conclusion: This is the first description of quantitative parameters characterizing vascular wall abnormalities in intracranial atherosclerosis. Despite its obviously intact state, vascular walls outside the intracranial AP was shown to be abnormal as well.