Abstract
Objective
To evaluate if knowledge of patient-specific inflow data in computational fluid dynamics simulations is required for the accurate calculation of intra-aneurysmal flow patterns and wall shear stress in an aneurysm of the anterior communicating artery (AcomA).
Materials and methods
3D digital subtraction angiography (3D-DSA) and phase contrast magnetic resonance (pcMRI) images were obtained in a 71-year old patient with an unruptured aneurysm of the anterior communicating artery (AcomA). A baseline computational flow dynamics simulation was performed using inflow boundary conditions measured with pcMRI. Intra-aneurysmal flow patterns, maximum, minimum and average values of wall shear stress and wall shear stress histograms were calculated. Five additional computational flow dynamics simulations were performed, in which simulated inflow from the right and left A1 segment was varied, while keeping the total inflow constant. Intra-aneurysmal flow patterns measured with pcMRI were qualitatively compared to intra-aneurysmal flow patterns derived from the simulations.
Results
Intra-aneurysmal flow patterns calculated in the baseline simulation were in good qualitative agreement with pcMRI measurements. Intra-aneurysmal flow patterns and wall shear stress changed considerably when inflow conditions were altered. Changes in the flow distribution between right and left A1 segments caused variations of the averaged wall shear stress as high as 43%.
Conclusion
Intra-aneurysmal flow patterns and wall shear stress in an AcomA aneurysm calculated with computational flow dynamics depended strongly on the flow distribution between A1 segments. Patient-specific flow data measured with pcMRI obtained prior to computational flow dynamics are necessary for an accurate simulation of intra-aneurysmal flow patterns and calculation of wall shear stress in AcomA aneurysms. Further studies may indicate if wall shear stress calculated with computational flow dynamics can predict aneurysm growth and/or rupture.
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Comment
In most of the previous paper dealing the hemodynamics simulation of cerebral aneurysms, the vessel shapes were patient-specific, but the inlet boundary condition (flow rate) was not patient-specific. The authors seem to have question about this point.
So, the authors carried out the hemodynamic simulation with a proper inlet boundary flow rate, which was measured using phase contrast MR. And they compared it with the simulation results obtained with various hypothetical inlet boundary flow rates.
The simulation results were compared in three aspects:
1. Velocity distribution in the cut plane of the aneurysm cavity, visualized with colored contour.
2. Temporally change of the shear stress on the aneurysm wall, visualized with line plot.
3. Distribution of the shear magnitude on the aneurysm wall, visualized with histogram.
The simulation results were analyzed, and the result was derived that different inlet boundary flow rates lead to different simulation results.
M. Shojima
Jichi Medical University, Japan
The authors have no financial relationships to disclose.
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Karmonik, C., Yen, C., Grossman, R.G. et al. Intra-aneurysmal flow patterns and wall shear stresses calculated with computational flow dynamics in an anterior communicating artery aneurysm depend on knowledge of patient-specific inflow rates. Acta Neurochir 151, 479–485 (2009). https://doi.org/10.1007/s00701-009-0247-z
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DOI: https://doi.org/10.1007/s00701-009-0247-z