Individual Research Project 07

Patient-specific prediction of aneurysm growth and rupture in the ascending thoracic aorta

Federica Galbiati – ESR 07

The growth of aortic aneurysms is associated with several mechano-chemo-biological interactions leading to modifications of the tissue structure including the fragmentation of elastin and changes in the amount and organization of collagen. So far, these mechanisms have been considered in a constitutive model based on the constrained mixture approach, where each constituent has an elastic constitutive response governed by an anisotropic strain energy function and an inelastic constitutive response governed first by a scalar [1–d]-type damage formulation and second by a permanent deformation gradient related to the growth. The model has been implemented as a user material in the Abaqus software. In this project, the ESR will apply the model to simulate the growth of ATAA (ascending thoracic aorta aneurysm) in patients for whom we have reconstructed the aortic geometry for several years (on going longitudinal study at the University Hospital of Saint-Etienne). In addition to the geometry, the ESR will also have access to hemodynamics through CFD analyses combined with 4D MRI also acquired longitudinally for these patients, and even stiffness of the wall through an inverse method based on RBF mesh morphing. All these data will be used to calibrate the finite-element model on a cohort of 20+ patients in order to better understand how aneurysms grow and how the damage localizes in the tissue. In view of the Digital Twin, the final goal will be to simulate numerically the scenario of growth and possible rupture for any patient’s aneurysm, just from the 4D MRI data, thus aiding the surgeon to take important decision such as surgical repair. The numerical processes will be automated through scripts and both commercial and open source solvers will be considered. After a preliminary assessment, the Python programming language for designing the scripts driving computational processes, the ABAQUS and Code Aster codes to run the structural calculations, and ANSYS Fluent and SimVascular software to performed CFD analyses have been identified as possible candidates.

Expected Results

• Calibrated model for the growth of ATAA..

• Automated computational procedure, as part of the Digital Twin.

• Results/conclusions from the studied cases.