Hemodynamic Analysis And Optimal Design Of Cardiac Aorta Structure For Biological 3D Printing

Cardiovascular diseases are the leading cause of the world’s disease burden,among which the aorta suffers the most severe impact and loss.Artificial blood vessel implantation is the final treatment for aortic disease.3D bioprinting artificial blood vessels have great potential in the field of artificial blood vessel implantation.However,due to the various constraints around the aorta and its complicated structural and the complex blood flow inside,there is a lack of three-dimensional model which meets individual specific needs at the physiological level as the manufacturing basis.The geometry and mechanical properties of artificial blood vessels can be improved by structure optimization.The paper used ascending aorta,aortic arch and its three branches as research objects,focused on the property of the influence of geometrical morphology of the artificial replacement of the target vessel segment on its degree of erosion and service life,based on the geometry considering medical images and anatomical principles,in order to propose an optimal design method of the target vessel segment considering the geometric parameters of the model,which is in accordance with the basic geometry of the target segment and considers its peripheral constraints.The model can reduce the level of erosion and thus improve the service life of the artificial replacement of the target segment.The main contributions of the thesis can be summarized as follows:Firstly,a parameterized 3D model of the target vessel segment was established to meet the specific needs of individuals,and the blood flow status of the target vessel segment in the heartbeat cycle was analyzed by using the finite element method.The distribution and trend of blood flow,wall pressure and wall shear stress in the target vascular segment at different stages were obtained,and the vulnerable areas of the target vascular segment were analyzed in combination with cardiovascular pathology.The results showed that the proximal sides of the three branches,the medial part of the descending aorta,and the medial part of the descending aorta have a relatively high risk of atherosclerosis,while the ascending aorta,the distal root of the three branches,and the lateral outlet of the aortic arch had a relatively high risk of aortic dissection.Then,based on the 3D model of the target vessel segment constructed and relatively clear pathological analysis indexes,the influence of different blood viscosity on different lesions prone areas was analyzed.The results showed that high blood viscosity could increase the risk of aortic dissection in the root region of the junction area between the lateral part of the descending aortic arch and the three branches,and increase the risk of atherosclerosis in the medial artery at the top of the aortic arch.At the same time,the effects of different structural parameters on different susceptible areas were analyzed.The results showed that the five target vessel segment geometric parameters which contains the ascending aorta and aortic arch intersection sagittal direction coordinates,the ascending aorta and aortic arch intersection coronal direction coordinates,the aortic arch top deflection angle,the distance between aortic arch vertex and its fore control point or its hind control point have an impact on the risk of arterial dissection which happens on aortic arch outlet lateral and left common carotid artery and the transition region of left subclavian artery,and the risk of atherosclerosis on the medial top of the aortic arch.Finally,aiming at the problem that the geometry of the artificial replacement of the target vessel segment affects the degree of erosion and its life,a Kriging proxy model optimization method combined with finite element analysis was proposed to obtain the optimal solution of the geometric parameters of the target vessel segment in the design space.The optimization results showed that the value of max wall shear stress peak in the target region decreases by 16.22%,which significantly reduces the degree of blood flow scouring in the region,thus improves the service life of the artificial replacement in the target segment.