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AJNR - American Journal of Neuroradiology

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Saccular Aneurysms on Straight and Curved Vessels Are Subject to Different Hemodynamics: Implications of Intravascular Stenting

H. Meng^a,b,c, Z. Wang^a,b,c, M. Kim^a,b,c, R.D. Ecker^a,b and L.N. Hopkins^a,b

^a Toshiba Stroke Research Center, University at Buffalo, State University of New York, Buffalo, NY
^b Department of Neurosurgery, University at Buffalo, State University of New York, Buffalo, NY
^c Department of Mechanical and Aerospace Engineering, University at Buffalo, State University of New York, Buffalo, NY

View larger version (66K): [in a new window]   Fig 1. Aneurysm model geometry. A, Sidewall aneurysm on a straight vessel (S) and aneurysms on curved vessels with different curvatures (C1–C3). Curvature is defined as C = 1/R, where R is the radius of curvature of the parent vessel. N indicates neck size; d, aneurysm diameter; , vessel diameter. B, Stent used in the flow experiment and mimicked in the CFD simulations (5 x 40 mm Wallstent). C, Computational mesh in a stented aneurysm model used for CFD analysis.

View larger version (14K): [in a new window]   Fig 2. Inflow momentum as a function of vessel curvature (zero curvature corresponds to the sidewall aneurysm) from CFD simulation (Re = 128). Inflow momentum is calculated at the interface between the aneurysm orifice and parent vessel. The values for both untreated and stented models are calculated, but only the untreated models are labeled with values to show the difference between the straight vessel model (S) and the curved vessel (C) models.

View larger version (69K): [in a new window]   Fig 3. CFD simulation (3D) of aneurysmal flow in the straight vessel model (S) and one of the curved vessel models (C3) (Re = 128). Plotted are 2-dimensional velocity fields in the center plane. Insert reveals flow sieving through the stent struts in the straight vessel model. Shown is the vertical velocity magnitude contour at the aneurysm–parent vessel interface.

View larger version (108K): [in a new window]   Fig 4. Dye visualization of the straight vessel model (S) and one of the curved vessel models (C3). The pictures are selected from the third image after the first appearance of dye in the aneurysm sac to represent the wash-in status.

View larger version (13K): [in a new window]   Fig 5. SI before and after stent placement as a function of vessel curvature for each model (S, straight; C, curved vessel) in the dye visualization experiment. As the curvature increases, SI decreases. Stent placement increases SI, but the increment is smaller in larger curvature models.

View larger version (25K): [in a new window]   Fig 6. WSS distribution at the distal aneurysm wall and distal vessel wall in straight (S) and curved (C) models before and after stent placement, calculated from CFD simulation (Re = 490). Color scale represents WSS values from <15 dynes/cm2 (deep blue) to >35 dynes/cm2 (bright red). The impact zone is defined as the area where WSS is >20 dyne/cm2, a value considered the upper limit for normal physiologic WSS.

View larger version (14K): [in a new window]   Fig 7. Impact zone for untreated and stented cases at various vessel curvatures, calculated from CFD simulation (Re = 490). The stent disturbs more impinging flow to decrease the impact zone at the moderately curved vessel, but the stent effect diminishes at the highly curved vessel.