Quantitative hemodynamic analysis of brain aneurysms at different locations

Abstract

Background and purpose: Studies have shown that the occurrence of brain aneurysms and risk of rupture vary between locations. However, the reason that aneurysms at different branches of the cerebral arteries have different clinical presentations is not clear. Because research has indicated that aneurysm hemodynamics may be one of the important factors related to aneurysm growth and rupture, our aim was to analyze and compare the flow parameters in aneurysms at different locations.

Materials and methods: A total of 24 patient-specific aneurysm models were constructed by using 3D rotational angiographic data for the hemodynamic simulation. Previously developed computational fluid dynamics software was applied to each aneurysm to simulate the blood-flow properties. Hemodynamic data at peak pulsatile flow were recorded, and wall shear stress (WSS) and flow rate in the aneurysms and parent arteries were quantitatively compared. To validate our method, a comparison with a previously reported technique was also performed.

Results: WSS and flow rate in the aneurysms at the peak of the cardiac cycle were found to differ in magnitude between different locations. Multiple comparisons among locations showed higher WSS and flow rate in middle cerebral artery aneurysms and lower WSS and flow rate in basilar artery and anterior communicating artery aneurysms.

Conclusions: We observed changes in hemodynamic values that may be related to aneurysm location. Further study of aneurysm locations with a large number of cases is needed to test this hypothesis.

Fig 1.

Schematic representations of regions for hemodynamic data analysis. A, Regions in the arteries of terminal or bifurcation aneurysms. B, Regions in the arteries of sidewall aneurysms. C, Regions in the aneurysm dome. D and E, Application to patient-specific aneurysm models are shown for a bifurcation aneurysm (D) and a sidewall aneurysm (E).

Fig 2.

Representative hemodynamic results for AcomA (A and B), MCA (C and D ), ICA (E and F ), and BA (G and H ) aneurysms. Top row is the 3DRA images obtained for each aneurysm during the clinical procedure. A diversity of aneurysms and complicated arterial structures can be observed. The middle row (flow pattern) and the bottom row (WSS) are the hemodynamic results obtained from the simulation. Flow pattern and WSS show differences among aneurysms, and each one has a unique pattern in the arteries and the aneurysms. WSS is in pascal units.

Fig 3.

WSS in aneurysms at each location. Note the average WSS in arteries and aneurysms and the average WSS in the entire aneurysm area.

Fig 4.

Flow rates in aneurysms at different locations. Note the average flow in arteries and aneurysms and the average flow velocity in the entire aneurysm area.

Fig 5.

A and B, Validation study comparing the hemodynamic results by using 6 regions (solid) and values collected from the entire dome and parent artery (method of Shojima et al) (hollow) shows the average WSS in the aneurysms (A ) and the average WSS in the parent arteries (B). Note in cases 5 and 8 that both methods show the same average WSS in the aneurysm.