A moving boundary meshless method to investigate thoracic aorta hemodynamics based on CT images and mesh morphing technique
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The crucial role of fluid dynamics in the thoracic aorta (TA) diseases is well established as well as the coupled usage of numerical simulations and medical images to investigate hemodynamic indicators. Nevertheless, to successfully translate the use of numerical simulations in clinical practice a high accuracy and low computational times are required. To accurately investigate TA hemodynamics the numerical simulations should include actual aorta wall motion. Moving boundary methods could be a promising instrument to overcome computational fluid dynamics (CFD) and fluid structure interaction (FSI) limitations that consist in the rigid wall hypothesis and high computational cost with assumptions about material properties, respectively. Mesh morphing approach turns out to be a useful instrument to replicate ascending aorta wall changes [1,2]. To increase the accuracy in fluid dynamic results also the motion of the remaining portion of TA should be consider. Thus, in this work a new strategy has been developed starting from CT images synchronized with cardiac cycle to simulate the actual motion of the entire TA. 3D models of TA have been reconstructed through segmentation for ten phases of cardiac cycle and a mesh morphing technique together with a spline interpolation have been implemented to obtain a mesh nodes mapping of aorta at each phase. The aortic wall displacement has been included in the CFD simulation setup and patient-specific boundary conditions of flow velocity and blood pressure have been considered. Moreover, a standard CFD simulation has been performed to compare hemodynamic results. The developed strategy allowed the replication of TA morphological changes and motion during the cardiac cycle with high accuracy and maintaining mesh quality. The results showed a delay in the flow waveform at a descending section compared to the inlet flow profile with respect to CFD simulation and differences in velocity distributions and main wall shear stress based indicators. These findings highlight the impact of TA wall motion on hemodynamics and thus the need of the involvement of actual aortic geometry changes into CFD simulations to obtain increasingly patient-specific results overcoming the main limitations of FSI technique.
