Towards Predicting Patient-Specific Flow-Diverter Treatment Outcomes for Bifurcation Aneurysms: From Implantation Rehearsal to Virtual Angiograms

Abstract

Despite accounting for the majority of all cerebral aneurysm cases, bifurcation aneurysms present many challenges to standard endovascular treatment techniques. This study examines the treatment of bifurcation aneurysms endovascularly with flow-diverting stents and presents an integrative computational modeling suite allowing for rehearsing all aspects of the treatment. Six bifurcation aneurysms are virtually treated with 70% porosity flow-diverters. Substantial reduction (>50%) in aneurysm inflow due to device deployment is predicted in addition to reductions in peak and average aneurysm wall shear stress to values considered physiologically normal. The subsequent impact of flow-diverter deployment on daughter vessels that are jailed by the device is investigated further, with a number of simulations conducted with increased outlet pressure conditions at jailed vessels. Increased outlet pressures at jailed daughter vessels are found to have little effect on device-induced aneurysm inflow reduction, but large variation (13–86%) is seen in the resulting reduction in daughter vessel flow rate. Finally, we propose a potentially powerful approach for validation of such models, by introducing an angiographic contrast model, with contrast transport modeled both before and after virtual treatment. Virtual angiograms and contrast residence curves are created, which offer unique clinical relevance and the potential for future in vivo verification of simulated results.

A Virtual Comparison of the eCLIPs Device and Conventional Flow-Diverters as Treatment for Cerebral Bifurcation Aneurysms

“…Performance with the FD BRAIDED device deployed in the opposite daughter vessel (left) is substantially improved. This better performance results from disrupting the fundamental flow pattern of the aneurysm dome, where flow now enters more centrally, and by the more tightly packed device struts restricting flow more—both effects documented in previous publications 22. This superior performance of the FD BRAIDED deployed in the left vessel is very visible in Fig.…”

“…Deployment and CFD modelling of these devices discussed in this paper were conducted previously with an identical meshing setup, boundary conditions and device sizing according to manufacturers’ recommendations. Details of these computations are referred to here for brevity and are available in the literature 22Table 1Size of conventional flow diverter device and eCLIPs device implanted into each aneurysm geometryAneurysmConventional device (FD BRAIDED ) sizeeCLIPs sizea13 × 25 mm3.25 mma24 × 20 mm3.25 mma34 × 20 mm3.25 mma43 × 20 mm3.25 mma53.5 × 20 mm3.25 mm…”

The Role of Hemodynamics in Intracranial Bifurcation Arteries after Aneurysm Treatment with Flow-Diverter Stents

“…It seems that changes in the forces to which endothelial cells are exposed may lead to vasomotor reaction in cerebral arteries. [17][18][19] Considering that this study does not include biologic events analysis (eg, thrombosis) and in view of current knowledge, it is audacious to link small WSS changes to vasoconstriction as the main explanation. The role played by hemodynamics in the endothelial-mediated constrictive mechanisms needs further investigations.…”

Association Between Aneurysmal Haemodynamics and Device Microstructural Characteristics After Flow-Diversion Treatments With Dual Stents of Different Sizes: A Numerical Study

“…For the included cases, we modeled flow-diversion treatments with the PED. Virtual deployment of the PED was realised through use of a previously reported and validated spring–mass method ( Spranger et al, 2015 ; Peach et al, 2016 ; Zhang et al, 2017b ). (See Supplementary Material 1 for a detailed description.)…”