Research On Evaluating Vascular Diseases Risk And Optimizing Treatment Based On Computational Biomechanics

Vascular diseases seriously threaten human health,about 290 million people in China suffer from cardiovascular-related diseases.Biomechanics plays an important role in the research of vascular diseases,and the evaluation of the risk of vascular diseases and the safety and effectiveness of treatment is tilting from the initial morphology to the biomechanical evaluation.From the perspective of computational biomechanics,this paper evaluates the risk of vascular diseases(specifically,post-stenotic dilatation,aortic tortuosity and acute type B aortic dissection)and establishes the mathematical models of Thoracic Endovascular Aortic Repair(TEVAR)and Magnetic Drug Carrier Particles(MDCPs)targeted therapy,aiming to provide theoretical bases for clinical disease re-search and surgical planning.Risk assessment:(1)By setting the control group,it is found that the accumula-tion of vortical structures with higher swirling intensity downstream of the coarctation segment of the aorta is the decisive factor for the occurrence of distal dilatation,which is also confirmed by the patient of aortic coarctation with good postoperative recovery.With the increase of coarctation degree of aorta,there is a significant increase in vortical structures with higher swirling intensity,accompanying by strong jets,which increases the risk of distal expansion(or even aneurysm-like expansion).(2)The 3D curvature and torsion parameters of differential geometry are proposed to display the local tortuosity of the aorta from two angles of "bend" and "torsion".This method overcomes the shortcom-ing of traditional methods in describing local details and anisotropic features.Moreover,hemodynamic simulation and linear regression show that aortic tortuosity is associated with higher risk,and the novel parameters could be used as evaluation indicators for the associated risk of aortic tortuosity.(3)According to morphological statistics(163 cases of aortic dissection and 120 cases of normal people),it is found that the occurrence of a-cute type B aortic dissection is related to the elongation of the proximal descending aortic segment.The dimensionless length ratio parameter could be used as a novel predictive indicators.The elongation of the proximal descending aortic segment causes aggressive hemodynamic forces,and the area with higher low and oscillatory shear probably corre-sponds to the location of the entry tear.Therefore,it is believed that the synergistic effect of the weakening of the vascular wall and the aggressive hemodynamic force caused by the elongation of the proximal descending aortic segment promotes the occurrence of dissection.TEVAR treatment:Based on the mutual interaction among blood,vascular wall and stent,a mathematical model of stent deployment in TEVAR surgery is established.The interference fit in mechanical assembly is introduced into TEVAR to achieve a tight con-nection between the vascular wall and the stent for the first time.The effects of stent implantation depth(oversize),length,material and shape on the Von-Mises stress and de-formation of the stent and the vascular wall are quantitatively evaluated.The deformation and Von-Mises stress of the vascular wall are positively correlated with the implantation depth of the stent,and negatively correlated with the implantation length and material stiffness.The Von-Mises stress of the stent reaches the maximum in the area where the curvature of the strut changes greatly,and is most significantly affected by the implanta-tion depth.Targeted drug therapy:Based on the discrete phase model,a mathematical model of MDCPs targeted treatment for atherosclerosis is established.The influence of unsmooth surface of the vascular wall and the plaque on MDCPs is taken into account,and the elastic modulus and Poisson’s ratio of MDCPs and plaque are employed to determine whether the MDCPs are deposited on the plaque.The therapeutic effect is evaluated by combining advantages(delivery efficiency of MDCPs)and disadvantages(plaque dam-age).The plaque damage is characterized by wall shear stress,and the delivery efficiency of MDCPs is counted through a combination of macroscopic(capture efficiency)and mi-croscopic(deposition+adhesion)methods.The influences of internal factors(plaque morphology)and external factors(external magnetic field configuration,intensity,the shape and size of MDCPs)on the therapeutic effect are analyzed.