Modeling of Endovascular Coiling for Cerebral Aneurysms: Effects of Friction on Coil Mechanical Behaviors

Abstract In this paper we develop a computational model of endovascular coiling for cerebral aneurysms to interpret the mechanical behavior of the coil during the deployment process into the aneurysm. Three-dimensional coil behavior, including large deflection, is expressed by corotational beam element formulation, and transitions of the coil configuration during deployment are obtained by solving the equation of motion while considering friction. Numerical examples of the straight-shape coil deployment to an idealized aneurysm via a catheter demonstrate that the coil forms an ordered loop structure at the initial stage of coil deployment, while axial buckling is found at the part of the coil just released from the catheter during deployment. Although the cause of the axial buckling can be well explained by frictional resistances exerted on the coil placed in the aneurysm, the post-buckling structure of the coil shows two patterns depending on the frictional coefficient. At low friction, the whole coil placed in the aneurysm slides along the aneurysm surface and maintains its ordered structure. At high friction, however, large deflection occurs where the coil has just been released from the catheter and after pushing itself into place in the aneurysm, the ordered coil structure collapses and formation of a disordered structure with uniform distribution ensues. The present model is valuable for interpreting the mechanical behavior of endovascular coils and for estimating the extent of spatial uniformity achieved by a coil in an aneurysm.