High-resolution 7T Vessel Wall Imaging for Aneurysms

Introduction: Unruptured intracranial aneurysms affect 0.4% to 3.2% of the global population. Aneurysm rupture can lead to life-threatening subarachnoid hemorrhage, with significant morbidity and mortality linked to various patient and aneurysmal factors. Current predictive models for aneurysm rupture overlook morphological aspects. High-resolution vessel wall imaging (VWI) has emerged as a key tool in evaluating aneurysm instability through wall thickness and enhancement, which indicate inflammation, growth, and rupture potential. Seven-tesla (7T) MRI technology may improve upon the limitations of 3T MRI, particularly for smaller aneurysms. This review highlights VWI features using 7T MRI

Methods: A literature search was conducted in PubMed, Ovid-Medline, and Embase for original research on aneurysm VWI using 7T MRI.

Results: Out of 54 initially screened studies, 14 were included. In diagnostics, of 78 lesions deemed suspicious for aneurysms on 3T MRI, 34 were confirmed as true aneurysms on 7T, while others were normal variants. The 7T MRI provided sufficient resolution to monitor basilar artery perforator aneurysms non-invasively. It produced sharper images than 3T, which often overestimated wall thickness. High-resolution VWI data indicated that larger aneurysms had thicker walls and increased enhancement, a marker for instability supported by histologic findings. Distinct enhancement patterns were observed between fusiform and saccular aneurysms, reflecting different pathologies. Additionally, focal adventitial wall enhancement (AWE) correlated with daughter sac formation, a known rupture risk factor, and thrombus intensity was positively related to wall thickness. VWI combined with hemodynamic studies showed lower wall shear stress in enhanced areas compared to non-enhanced regions.

Conclusion : Existing predictive models for aneurysm rupture risk do not incorporate aneurysmal morphology. Non-invasive high-resolution VWI could help identify unstable aneurysms at high rupture risk. However, the absence of prospective validation limits clinical application, highlighting the need for real-world data to confirm HR-VWI as a reliable marker for aneurysm instability and rupture.