Abstract 008: Morphomechanical Analysis of Saccular Aneurysms
Authors: Gudino Andres , Sanchez Sebastian , Ojeda Diego J , Miller Jacob , Galloy Adam , Nino Marco , Sagues Elena , Saleem Arshaq , Wang Bincheng , Samaniego Edgar 
Published: March 2024

Introduction
An irregular morphology is considered a high‐risk feature of unruptured intracranial aneurysms. Some of these aneurysms may have blebs where there is a high likelihood of rupture. The process of aneurysm rupture is dynamic and involves factors such as aneurysm geometry, flow dynamics, and aneurysmal wall enhancement. In our study, we aimed to conduct a comprehensive analysis of brain aneurysms, specifically focusing on irregular and regular aneurysms. This analysis included the examination of aneurysmal wall enhancement (AWE), computational fluid dynamics (CFD), and finite element analysis (FEA).

Methods
The study focused exclusively on unruptured aneurysms and employed high‐resolution vessel wall imaging using 3T MRI. Aneurysms were classified as irregular if they displayed a bleb or multiple lobes. A 3D segmentation of the aneurysm and vessel was generated using 3D Slicer software. Orthogonal spokes were extended from the segmentation into the vessel wall, enabling the creation of intensity (SI) heatmaps. Aneurysmal wall enhancement (AWE) was calculated based on the post‐contrast SI. Furthermore, wall tension (WT) was determined using FEA, and time‐averaged wall shear stress (TAWSS) was computed through CFD utilizing the 3D segmentation. To identify regions of notable activity within the aneurysm, an analysis was conducted by examining values exceeding the 50th percentile threshold. This approach facilitated the inclusion of areas demonstrating heightened activity within the aneurysm. The study comprised two primary analyses: first, a comparison between regular and irregular aneurysms, and second, a secondary analysis that focused specifically on aneurysms with blebs. During this analysis, the bleb, body, and neck regions were isolated for comparative evaluation among different compartments within the aneurysms.

Results
The study included a total of forty‐seven unruptured saccular aneurysms, with 38% (18/47) classified as having irregular morphology. Comparing aneurysms with irregular morphology to those with regular morphology, it was observed that irregular aneurysms exhibited higher WT (p=0.05) and lower TAWSS (p=0.04). Among the irregular aneurysms, 61% (11/18) were found to have blebs. Within aneurysms containing blebs, significant differences were observed in terms of WT and AWE between the bleb, neck, and aneurysm body (p<0.001 and p=0.03, respectively). Specifically, the blebs exhibited the highest AWE within the aneurysm, followed by the aneurysm body and the neck. The neck exhibited the highest value of WT, followed by the aneurysm body and the bleb. Finally, the neck also demonstrated the highest value of TAWSS, followed by the aneurysm body and the bleb.

Conclusion
Irregular aneurysms had a higher WT and lower TAWSS. Furthermore, the morphomechanical characteristics of irregular aneurysms varied between the aneurysm neck and body, indicating distinct properties in these regions. Unstable regions of the aneurysm, such as blebs, exhibited elevated AWE along with low TAWSS and WT.