gms | German Medical Science

Objective: Computational fluid dynamics (CFD) is a powerful tool to simulate flow and derived quantities like wall shear stress, pressure and impingement forces in cerebral aneurysms. It has been shown, that CFD can predict thin-walled and vulnerable aneurysm regions, which can be a valuable information for therapy planning. The aim of our study was to translate this promising method from bench to bedside by developing a reliable, fast and user-friendly tool for neurosurgeons for operative planning as well as for scientific research on aneurysm initiation, growth and rupture.

Methods: We developed a software tool which combines all necessary features to compute the flow field in the aneurysm using 3D rotational angiography data. This includes a semi-automatic workflow for aneurysm segmentation, fully automated numerical mesh generation (open source library cfMesh v1.1.) and flow computation (OpenFOAM) and visualization of streamlines and morphological and hemodynamic parameters often used for rupture risk evaluation, like Size Ratio (SR) and Wall Shear Stress (WSS).

Results: The Aneurysm Forecast tool allows to obtain reliable CFD results in less than thirty minutes for even acute cases. It was rated as user-friendly by practicing neurosurgeons after an initial training. We conducted convergence studies on input parameters like mesh size, optimal length of inlet and outlets and evaluated the influence of flow split on the CFD results. Thus, we defined optimal input parameters to obtain reliable and stable, but also fast results. Nevertheless, the software is open to choose different input parameters for scientific use. The CFD results could be visualized in an in-house developed 3D-viewer in an operative setting, including craniotomy and positioning, allowing patient-specific dissection planning (see Figure 1 [Fig. 1] and Figure 2 [Fig. 2]), and also be exported to navigation for intraoperative use.

Conclusion: We present a novel assistance tool for aneurysm surgery which provides fast and reliable predictions about vulnerable aneurysm regions in less than thirty minutes for even emergency cases. Visualization of preoperative CFD simulations helps the surgeon to recognize thin-walled and vulnerable regions correlating to low wall shear stress and high pressure. A CFD-adjusted approach and dissection of the aneurysm can potentially improve surgical tactics to prevent intraoperative rupture. Furthermore, this user-friendly and adjustable tool is suitable for clinical and fundamental research.