Investigating Particle Paths in Intracranial Aneurysms: A Parametric Study

A large part of computational fluid dynamics (CFD) studies in hemodynamics concentrates on the berry-like bulgings on cerebral vessel walls, called intracranial aneurysms (IA). One technique is the calculation of particle paths, which can help understand important physiological processes like thrombus formation or drug propagation. The problem is that the particle paths can display chaotic nature even in simple flows, thus, investigating the effects of parameters on the particle paths is essential. The method used in this study consists of four steps. The first step is to voxelize the observed domain into a uniform voxel grid, the second step is to simulate the velocity flow field using the lattice-Boltzmann method, then to calculate one million particle paths using a fourth-order Runge-Kutta integrator. Lastly, the final step is the calculation of the relative perimeter, relative area and their ratio (P/A ratio) for each outlet when the particle release plane is colored according to the outlets the particles took. Five patient-specific cases were investigated. After a voxel size and integrator time step dependence study, the effect of the presence of the aneurysm sack and the particle release time within the heart cycle were assessed. Based on five geometries, the presence of the aneurysm sac increases the P/A ratio (which is a direct link to the chaotic nature of the particle paths), and when the particles are released near the peak and the decelerating phase of the heart cycle, the P/A ratio also significantly increases.