The objective of this research is the fluid dynamic analysis of the blood flow in arteries in the presence of pathological dilations (aneurysms). The problem is of significant interest in the medical and scientific fields, since the most frequent and dramatic clinical event linked to the presence of an aneurysm is its rupture and consequent hemorrhage, with extremely serious clinical consequences. Nowadays, the most widely used criterion in the medical field to predict the aneurysm rupture is based on the maximum diameter value. Nevertheless, it is well known that small aneurysms rupture while some large ones remain intact for a long time. In this context, the study of the fluid dynamics field in the dilated artery is fundamental, since the crucial role played by hemodynamics in the growth and possible rupture of the aneurysm.
This study analyzes the influence of the main hemodynamic factors on the evolution of the artery dilatation as a function of its geometry, size, tortuosity and the presence of any intraluminal thrombus. The numerical investigation will be carried out both in idealized aneurysmal geometries and in patient-specific aneurysm models, which will be reconstructed from the medical imaging (CT, MRI). Blood flow will be analyzed in physiological conditions of pulsating motion and suitable non-Newtonian rheological models will be adopted.
In particular, wall shear stresses and vorticity evolution during the cardiac cycle distribution we will be analyzed in order to establish a possible link between these quantities and the aneurysm growth and provide physicians with additional and essential diagnostic tools in the treatment of the disease and planning surgery.
This research has the objective to analyse the blood flow into aneurysms in order to assess the vulnerability of the aortic wall and furnish a useful diagnostic tool for the comprehension of the individual pathology, supporting the clinical management of the aneurysmal disease.
In addition to being part of an extremely innovative research context, there are several elements of originality proposed in the project. From the point of view of the numerical investigation, following the most recent works in the literature, medical image analysis techniques will be used, in order to obtain patient-specific aneurysm models, and more realistic and physiological results. Indeed, many numerical investigations on the hemodynamics in aneurysm models are often based on the assumption of idealised geometries. This hypothesis leads to solutions that may be of interest for some of the intended objectives , but may be unreliable for the study of blood flow in the complex real geometries and the determination of aneurysm rupture. On the other hand, the inclusion of a patient-specific model in the analysis of the influence of hemodynamic factors on the evolution of the disease is a significantly challenging task.
Taking into account the previous observations, one of the main and innovative focuses of this research will consist in conducting numerical simulations of the blood flow in diseased artery, using computational fluid dynamics techniques in patient-specific models, reconstructed from medical imaging (CT and MRI).
Moreover, in order to better understand the influence of the pulsating blood flow on the growth and progression of aneurysmal disease, the evolution of the wall shear stress and vortex core distributions during the cardiac cycle will be considered. In this context, on the basis of the obtained numerical results, the subsequent evaluation of the residence time near the walls of the blood cells is another innovative objective. In this way, in fact, it is possible to predict the possible intraluminal thrombus deposition, which is associated with weakening and thinning of the artery wall and consequent possible rupture of the aneurysm.
Furthermore, in the numerical investigations different physiological patient-specific condition will be assigned at the boundaries, in order to evaluate the sensibility of the blood flow into the bulges to the inlet and outlet boundary conditions. Obviously, the effect of specific parameters of the aneurysmal geometries on the flow field evolution, in particular tortuosity and neck angle, will also be analysed.
In addition to the previous consideration, the analysis of the influence of the aneurysm geometry, in term of presence of inflection in the aneurysm centerline, well be investigated. To the best of our knowledge, this aspect is not already investigated, although some our first results suggests that it can play a relevant role in the vorticity distribution an consequent hemodynamic field.