gms | German Medical Science

Objective: Computational fluid dynamics (CFD) is a powerful tool to simulate flow and related forces like wall shear stress, pressure and impingement forces in cerebral aneurysms. This allows to predict regions of thin wall and high pressure prone to rupture within the aneurysm. We used intraoperative indocyanine green video angiography (ICG) in aneurysm surgery to validate CFD results and proofed the value of intraoperative visualization of these information to the surgeon during aneurysm surgery potentially changing the way of approach and aneurysm dissection.

Methods: In patients with incidental aneurysms preoperative 3D mesh-models were built using 3D rotational angiography slices. Amira (Visualization Sciences Group, USA) software package v. 5.6. and 'ANSYS' software was used for CFD. We investigated flow velocity, wall pressure, impingement point (IP) and wall shear stress (WSS). Information were transferred it into our navigation system (Kolibri, Brainlab, München). Intraoperative Indocyanine green (ICG) video angiography during surgery were screened for visible flow patterns. To visualize the flow patterns we used color-coded point of time of maximum gradient using the HSV color model. For post-processing visualization of the results and comparison to the ICG video analyses we used Avizo Wind 3D analysis software v 7.1.1 (Visualization Sciences Group SAS, USA).

Results: ICG video angiography revealed meaningful flow patterns in 8 of 12 cases. The streamline patterns of the CFD simulations correlated well with the flow seen in the ICG video angiography in all cases. The main streamlines, vortices and impingement points could be identified depending on the intraoperative angle of view. Intraoperative visualization of CFD revealed to be a useful tool in aneurysm clipping of incidental aneurysms. As previously reported, regions of low wall shear stress were confirmed to show a thin and delicate wall. Surgeons tried to avoid the regions of low wall shear stress and high pressure during the initial part of dissection appreciating the information of the CFD.

Conclusion: We present a novel assistance tool for aneurysm surgery. Visualization of CFD during operation helps the surgeon to recognize regions of low wall shear stress and high pressure prone to rupture. Validation of CFD was done by ICG video angiography and revealed good correlation to the CFD results. An CFD-adjusted approach and dissection of the aneurysm can potentially help to prevent intraoperative rupture.