A Highly Automated Computational Method for Modeling of Intracranial Aneurysm Hemodynamics

Figure 1. Preparation of angiogram data for the automated flow simulation. (Left) 3D angiogram of vessels with a target aneurysm identified. (Right) Cartesian ROI set around the target aneurysm with the inflow vessel identified. Green dots represent the center of each face of the Cartesian ROI.

Figure 2. Identifying lumen region by a region growing algorithm. (Left) Original grayscale image with the intensity (I). (Right) Identified lumen with the threshold intensity, I0 = 500. The region for which intensity, I, greater than the threshold, I0 is identified as lumen and the masking function value M is set to 1; otherwise M = 0.

Figure 3. (A) Level-set function ϕ defined by the image intensity. The lumen wall surface is defined by ϕ = 0. (B) Distance from the Cartesian grid point to the lumen wall location.

Figure 4. A schematic describing the imposition of wall boundary condition. The rectangle with dashed line represents a computational cell. Triangle symbol indicates the cell face center where the boundary velocity, UBC is imposed. Detailed description is provided in the text.

Figure 5. Vessel center line (s→) and radius (R′→) vectors. The vessel/aneurysm geometry is automatically segmented in the Cartesian ROI. The center line vector is defined by the vessel center points (red circle symbols) and the vessel radius vector is calculated from the in-plane radius vector (R→).

Figure 6. Schematic describing of the calculation of velocity gradient near the wall. Solid line: Vessel wall boundary identified by the level-set function. Rectangle with dashed line: A computational cell adjacent to the wall. Triangle symbol: The cell face center where the boundary velocity is imposed.

Figure 7. 3D angiograms of patient-specific intracranial aneurysm cases (A–G).

Figure 8. Automatically segmented aneurysm and vessel geometries using the present region-growing algorithm for the sample cases (A–G). Target aneurysm and inflow direction are marked.

Figure 9. The results of automated hemodynamic simulations using the present immersed boundary, level-set method for the sample cases (A–G). Streamtraces colored by the normalized velocity magnitude,|u→|/U0. The color contours are truncated at the range shown in the color bar for the best visualization of local distributions.

Figure 10. The results of automated hemodynamic simulations using the present immersed boundary, level-set method for the sample cases (A–G). Iso-surfaces of ϕ = 0 are plotted and colored by the calculated magnitude of wall shear stress (unit in kPa). The color contours are truncated at the range shown in the color bar for the best visualization of local distributions.