Computational Approach to Quantifying Hemodynamic Forces in Giant Cerebral Aneurysms

A and B, Phase-contrast MR images acquired transverse to the carotid (A) and basilar (B) arteries.

C, Velocity waveform shows mean flow through the basilar artery during one cardiac cycle.

Computational fluid dynamics results in the patient-specific geometry with velocity boundary conditions as determined in vivo by MR velocimetry.

A, Calculated velocity field (m/s). Note highly asymmetric flow secondary to near occlusion of the right vertebral artery. There is a large region of slow recirulating flow (blue) in the pouch of the aneurysm.

B, Calculated distribution of pressure (range from 0 to 150 pascal). The pressure distribution has no regions of pronounced increased pressure, with a smooth drop from inlet to outlet vessels.

Calculated wall shear stress along the lateral side of the vertebrobasilar system shown in Fig 1. The variable S is the distance measured along the outside wall, which includes the vertebral artery to be occluded. Shear stress is shown for symmetric inflow (solid line) and for simulated occlusion of the ipsilateral vertebral artery (dotted line).

Coronal maximum intensity projection of a contrast-enhanced MR angiographic study in a patient with a fusiform basilar aneurysm. The vertebral and basilar arteries have been selected from the full data set. Also noted is a stenosis of the right vertebral artery.

Plots of changes in velocity (dashed line) and volume flow (solid line) that are predicted by theory in response to increasing stenosis. Note that conservation of flow predicts a velocity increase for relatively small increases in stenosis, but that volume flow only starts to drop appreciably once the stenosis becomes hemodynamically limiting (ie, after the stenosis exceeds approximately 70%).

Computational fluid dynamics results in the patient-specific geometry assuming that there is an equal flow rate through the vertebral arteries.

A, Calculated velocity field (m/s). A high velocity jet is predicted through the stenotic vertebral artery impinging on the wall of the aneurysm. Flow reciruclation is noted on both sides of the jet.

B, Calculated distribution of pressure (range from 0 to 150 pascal). The pressure distribution shows a region of pronounced elevation of pressure on the outside wall of the aneurysm.