Morphological Evolution And Rupture Risk Factors Of Aneurysm Under Mechanical Mechanism

The phenomenon of local enlargement and deformation of intracranial artery wall when the blood flow changes is called intracranial aneurysm,which is a common vascular disease with high morbidity and mortality.The formation of aneurysm is influenced by physiology,morphology,hemodynamics and other factors.At present,the lack of criteria for determining aneurysm rupture causes great mental pressure to patients.Aneurysms are traumatic treatment,which has an impact on the health of patients.Most patients choose conservative treatment,so it is necessary to identify aneurysm and determine its risk.It is of great significance to study the formation and evolution mechanism of aneurysms by means of numerical simulation to provide suggestions for clinical diagnosis.Analytic Hierarchy Process(AHP)was used to conduct qualitative and quantitative analysis on the non-hemodynamic factors affecting aneurysm,and it was concluded that the weight of each influencing factor and the morphological parameters such as aneurysm diameter were important factors for aneurysm rupture.According to the results of more than 500 cases of angiography,the morphological factors of aneurysm formation were analyzed.It was found that when the vascular tree did not satisfy Mur Murry’s Law and the fractionation coefficient was less than 0.98,aneurysm formation was highly likely,and aneurysm volume also had a certain relationship with the bifurcation coefficient.There are complex factors in the formation of specific aneurysms,among which mechanical factors are the main factors.Therefore,the mechanism of aneurysm formation was studied in this paper from the perspective of fluid mechanics and solid mechanics.ANSYS APDL,balloon burst test and rubber constitutive equation were used to study the rupture mechanism of aneurysm.Meanwhile,fluid-structure coupling analysis was carried out to verify the prediction mechanism.The formation of aneurysm evolves from bulge-ellipsoid-spherical.Since the shape optimization of U-shaped tube has the same trend as vessel remodeling,the location where bifurcation vessels are prone to produce aneurysms under the action of pulsating flow can be inferred according to this mechanism.Assuming that the performance of vessels is similar to that of rubber material,it can be deduced that aneurysms will rupture when the comprehensive elongation caused by vessel wall deformation reaches a certain value.Considering the influence of hypertension on aneurysms,different controlled experiments were set to study the influence of different outlet pressure changes of each vessel on aneurysms.The results showed that the decrease of pressure difference would increase the flow rate of blood in the tumor,accelerate the changes of blood in the tumor,increase the impact on the vascular wall,and increase the risk of aneurysm rupture.When the outlet pressure at both ends of the same distance from the aneurysm is different,the blood flow pattern in the aneurysm will also be affected by the incident direction,Angle,tumor to neck ratio of the tumor and other factors.