## 4 Discussion  
The results obtained and presented in this work are only partially comparable with the literature on studies of aneurysms or endoprostheses [1; 2; 3; 6; 8; 10; 11], since the cases are dealt with separately or through the CFD study of the reconstructed aorta or the study of the stent/graft, which is always simplified at the level of geometry. The simplification on the geometry considering a perfectly tubular vessel with a straight axis and the stent/graft also allows faster analyses with less computational effort. The simplification of the modeling is therefore acceptable when one focuses on the study of the modeling of the aneurysm and its evolution, but not when the objective is, as in this work, to show the benefits of a personalized target prosthesis achieved by current medicine in the major fields of bioengineering and orthopedics neurosurgery, but still not reached in vascular surgery. The conducted CFD analyses have highlighted the advantages of using a patient-specific stent-graft. The wall shear stress (WSS), pressure, velocity, and the flow pattern at systole peak are the hemodynamic in-depth variables in all three fluid models in CFD analyses. In line with various studies in the literature [6; 8; 56; 57], it is noted that the wall shear stress at the site of the aneurysm is zero. This indicates that the blood flow does not exert tangential stresses on the wall due to the presence of low-velocity areas in the site, as can be seen in Figure 12. The maximum WSS is in branches: in the conventional graft, it is 184.6 Pa, while it is 142 Pa in the patient-specific graft. The use of a patient-specific graft reduces the maximum WSS by about 23% to the vessel and exhibits a distribution of wall shear stress that is more uniform than other models. The flow pattern shown in the conventional graft is not yet in the regime condition, and it is very different to the flow pattern of a patient-specific graft. This aspect is associated to the morphology of the graft used; the patient-specific one accommodates the vessel morphology and does not alter the vascular physiology. As regard the maximum velocity, a value of 4.6 m/s is reached in the patient-specific graft, while for the conventional graft, the value is 4.2 m/s. Note that the use of grafts improves the pressure profile, at 17 kPa, but the curvatures are still complicated areas with high pressure values (in particular, in the patient-specific graft). The FEM analysis of the aortic wall provided a good and reliable overview of the wall stress distribution, as shown in Figure 14. Although the peak values are concentrated on the ramifications--areas of concentration of tension--it is interesting to note that at the level of the aneurysm, the posterior part is most compromised. The results obtained, although relating to dynamic and non-FSI analysis, allow us to visualize the main characteristics regarding the distribution of the wall stress and, therefore, the areas at risk of failure. On the other hand, the model used presents some simplifications, such as the absence of calcifications and ILT and the assumption of a uniform thickness and shell model, which influence the wall stress distribution and the pathogenesis of the aneurysm [10; 58; 59]. As already widely discussed, FSI analysis provides more accurate results by modeling situations similar to in vivo circumstances [56]. In fact, in this case, it allowed the evaluation of wall stress and pressure on the graft by subjecting it directly to the fluid dynamic condition of interest (one-way coupling). Higher values and the peaks are near to the mesenteric branch's junction. This result is due to the birth of shape drag. The drag is the reason that the flow increases its kinetic energy, and therefore, in those areas, the flow becomes turbulent. For this reason, the geometry is the cause of the stress peaks. The same applies to the renal arteries, but the wall stress values are lower. The lack of a stent causes the DACRON to become excessively deformed. It is.