Modelling flow-diverting stent as porous medium with different permeabilities in the treatment of intracranial aneurysms: a comparison of a successfully treated case and an unsuccessful one

Using a porous medium as a computational model for the real flow-diverting (FD) stent in computational fluid dynamics (CFD) improves the simulation efficiency. Adjustment of permeability level of the applied porous medium can result in various flow-resistance effects, which impact on the flow dynamics around and inside the aneurysm dome. Moreover, diversity in patient-specific aneurysm geometry also contributes to the difference in both the resistance force induced by the FD device and the aneurysmal haemodynamics. However, few studies have discussed the relationship between the setting of permeability and the intra-aneurysmal haemodynamics with different aneurysms. In this study, in order to distinguish FD stents with different porosity, we simulated the porous medium stent with a range of permeabilities, respectively in a successfully treated aneurysm and an unsuccessfully treated one observed clinically. Haemodynamic parameters of intra-aneurysm mass flow rate (MFR) and energy loss (EL) were calculated to investigate their response to the alteration of permeability, as well as to the aneurysm morphology. In comparison between the two patient-specific aneurysms, we found marked changes (70 and 40 % in MFR, 40 and 35 % in EL, respectively with successful and unsuccessful cases) in the aneurysmal haemodynamics as the porosity level of the implanted FD stents was increased by a factor of 25. The simulation results showed considerable differences in the relative flow- diversion between the clinically observed successful and unsuccessful case (up to 30 % in MFR and 45 % in EL). This study will help to provide future FD modellers with information about suitable selection of permeability level for different aneurysm cases.