Study On Design And Performance Of Nickel Titanium Alloy Bulge-Type Stent Based On Medical Image Processing

Aortic dissection is an extremely dangerous aortic disease which has affected people's health and daily life seriously.It is the highest incidence of aortic disease in China.But it can effectively be cured by thoracic endovascular aortic repair(TEVAR)with sealing the proximal tear and to promote the formation of false lumen thrombosis.Stent grafts,as the main equipment for TEVAR treatment,play an important role in the reconstruction of blood pathway and acceleration of vascular remodeling.The medical images of patients with aortic dissection were an important specification for selecting the appropriate stent graft,and was also the major source of the future design for medical vascular stent graft oriented to patient individual requirement.The biomechanical performance of stent was an important index to evaluate the curative effect of aortic disease.Finite element analysis(FEA),as a research method,has been widely used in the field of medicine.It can be used to evaluate and predict the stress state after the implantation into vessel.In this study,based on the phenomenon of dissection of distal regurgitation and medical imaging data of patients,a new type of nickel titanium alloy stent with variable cross-section was designed.It exerted a certain pressure on the intima by segment and to accelerate the false lumen of proximal false lumen thrombus,achieving a positive therapeutic effect.Through the extraction and medical image processing,it can be directly obtained of the important parameters with the size and morphology of the dissection.The support performance can be strongly influenced by the changes geometric parameters by finite element analysis:by increasing wire diameter and bulge part's arrangement,the supporting force was increased,while it was reduced when bulge part's length was increased;the support performance is better when bulging degree was 8 mm.The wire diameter and the bulge part's length had more remarkable influence on supporting properties than the bulge degree of the stents and arrangement of stents.Through theoretical calculation and error analysis,the theory of the radial support force and the error range of the corresponding support were obtained.Under the condition of this study,the best combination of parameters consists of wire diameter with 0.5 mm,the length of the bulging part was 50 mm,3 stent rings arrangement on the bulging part and the bulging degree was 12 mm.By testing the biomechanical properties of the intima,the parameters can be obtained and it was used to provide important and reasonable evidence:the radial force should not be overdesigned the intima's physiological limits,by changing the geometric parameters,in order to avoid severe postoperative complications which caused by mismatch of biomechanical properties between stent grafts and intima.The CFD simulation results show that,without treatment of distal tears,one of them near may become a new entrance to provide continuous perfusion for false lumen of dissection.The bulge-type stent could effectively block the regurgitation phenomenon of dissection.The result of the experiment in vitro can be used to verify the validity of the CFD simulation.