Three-Dimensional Modeling And Hemodynamic Simulation Of Human Type B Aortic Dissection

Due to the development of productivity,people's material conditions are more diverse,lifestyle habits change,and medical technology progress,the detection rate of cardiovascular diseases is increasing year by year,of which type B aortic dissection is one of the representative cardiovascular diseases.Type B aortic dissection occurs in the descending aorta.The intima of the blood vessel is torn to form a tear.The teared intima divides the normal blood vessel into two parts,forming two blood vessel channels,the true and the false.At present,the long-term evolution mechanism of type B aortic dissection and its impact on cardiovascular disease are mostly dependent on clinical data collection,which can not be effectively inferred and prevented.A large number of studies have shown that hemodynamics is closely related to the occurrence and development of type B aortic dissection.Using computer numerical simulation to simulate hemodynamic analysis is an important research means to explore the hemodynamics in the occurrence and development of type B aortic dissection,but it is difficult to model type B aortic dissection based on human CT scan.In view of the single type,simple structure and inability to represent the real human blood vessels of the models currently studied,based on the CT medical image data of the real type B aortic dissection patients,this paper uses the medical image extraction software Mimics and the image difference algorithm of Boolean operation to realize the cavitation and variety of the models,and establishes the simulation of normal aortic vessels and operations.The first two models,as well as the multi-break model represented by three breaks,the proximal closure model and the distal closure model,consist of five models.On the basis of studying and discussing the numerical calculation of blood flow field and the basic mathematical model theory of finite element boundary loading,the five models are analyzed and discussed in terms of velocity streamline,wall pressure and wall shear stress by using the finite element simulation analysis software of hydrodynamics.The results of this study show that:(1)The results of finite element simulation conform to the relevant physical and mathematical principles,especially the Bernoulli principle between the wall pressure and flow velocity of the five models.It illustrates the feasibility and authenticity of using Mimics software to construct three-dimensional model based on real CT medical image data and the reliability of finite element simulation.(2)Preoperative finite element simulation results of B-type aortic dissection with two or more breaks show that turbulent eddies are easy to form at the proximal breaks of the pseudolumen and continue to tear the proximal breaks,and the greater the velocity of the aortic entrance,the easier the turbulent eddies are to form.There is no disordered flow line in the true cavity,and the flow line is smooth and regular.(3)Finite element simulation analysis of B-type aortic dissection with two or more breaks shows that the velocity difference and wall pressure difference between the true and false lumen of multi-breaks aortic dissection are smaller,and the wall shear stress distribution is more uniform;the velocity difference and wall pressure difference between the true and false lumen of B-type aortic dissection with two breaks are larger,the wall mechanical load distribution is uneven,and the false lumen will continuously squeeze the true lumen to make the true lumen enter.One step narrowing leads to the enlargement of the pseudolumen or the formation of new breaks,i.e.Two-break type B aortic dissection tends to develop into multi-break type B aortic dissection.(4)For typical type B aortic dissection with two breaks,the closure of proximal and distal breaks was performed by finite element analysis.It was found that the closure of proximal breaks should be preferred.After closure of proximal breaks,the wall pressure and wall shear stress in the pseudolumen decreased,which contributed to the isolation and thrombosis of the pseudolumen and improved the blood supply function of the true lumen.Closure of distal rupture,though it can not form blood flow pathway in the pseudolumen,leads to increased pressure in the pseudolumen,and has the risk of expanding the pseudolumen to form new rupture.