Comparative Assessment of Biomechanical Parameters in Subjects With Multiple Cerebral Aneurysms Using Fluid--Structure Interaction Simulations

TL;DR

This study uses fluid-structure interaction simulations to compare biomechanical factors in stable and growing cerebral aneurysms within the same subjects, identifying key stress patterns associated with aneurysm growth.

Contribution

It introduces a novel biomechanical analysis approach and a new metric, the oscillatory stress index, to better understand aneurysm progression.

Findings

Growing aneurysms show higher low shear and wall displacement.

Regions of low shear and high oscillatory stress are linked to aneurysm growth.

Stable aneurysms lack significant regions of oscillatory stress.

Abstract

Cerebral aneurysm progression is a result of a complex interplay of the biomechanical and clinical risk factors that drive aneurysmal growth and rupture. Subjects with multiple aneurysms are unique cases wherein clinical risk factors are expected to affect each aneurysm equally, thus allowing for disentangling the effect of biomechanical factors on aneurysmal growth. Towards this end, we performed a comparative computational fluid--structure interaction analysis of aneurysmal biomechanics in image-based models of stable and growing aneurysms in the same subjects, using the cardiovascular simulation platform SimVascular. We observed that areas exposed to low shear and the median peak systolic arterial wall displacement were higher by factors of 2 or more and 1.5, respectively, in growing aneurysms as compared to stable aneurysms. Furthermore, we defined a novel metric, the oscillatory stress index (OStI), that indicates locations of oscillating arterial wall stresses. We observed that growing aneurysms were characterized by regions of combined low wall shear and high OStI, which we hypothesize to be associated with regions of collagen degradation and remodeling. Such regions were either absent or below 5% of the surface area in stable aneurysms. Our results lay the groundwork for future studies in larger cohorts of subjects, to evaluate the statistical significance of these biomechanical parameters in cerebral aneurysm growth.