Impact of Wall Property and Flow Rate Assumptions on Simulations of Flow-Induced Vibration of Intracranial Aneurysms

Recent high-fidelity fluid-structure interaction (FSI) simulations of cerebral aneurysms have revealed flow-induced wall vibrations. However, those simulations were conducted under simplified conditions, and the robustness of the predicted vibrations remains unknown. This study aimed to advance the physiological accuracy of previous models and to investigate the sensitivity to parameter uncertainty. We compared the previously used near-linear St. Venant-Kirchhoff wall model with a three-term hyperelastic Mooney-Rivlin (MR3) model fitted to experimental data and also modeled effects of surrounding cerebrospinal fluid (CSF). We then varied flow rate (1.83 mL/s  $\pm$  25%), wall stiffness (soft, medium, stiff), and wall thickness (0.25  $\pm$  0.1 mm). Our main findings for the four aneurysms considered were as follows: the MR3 model led to an average increase of 35% in pulsation and 240% in vibration amplitude, along with an 18% decrease in frequency. Viscous damping by the CSF reduced the vibration amplitude by 68% but did not affect the frequency or pulsation. Changes in flow rate had no effect on pulsation but increased vibration amplitude by 246%. Wall stiffness and thickness had a comparatively smaller impact on vibration, altering amplitude by 36% and 82% and frequency by 20% and 8%. In conclusion, the more advanced models led to a decrease of vibration amplitude and frequency during the cardiac cycle, consistent with clinical observations. Like computational fluid dynamics, FSI simulations can be sensitive to flow rates but are otherwise robust and can provide a fundamental understanding of aneurysm wall vibration without precise knowledge of wall properties.