| Aortic dissection is a kind of dangerous cardiovascular disease with sudden onset,rapid development and high mortality in clinical medicine.In recent years,with the improvement of people's living standard and the change of dietary habits,the cases of aortic dissection have also appeared an obvious increasing trend.The main thoracic cavity repair with covered stent is an effective method to treat btype aortic dissection.However,the influence of stent placement and stent structure on patients could not be determined before the stent implantation,which could only be determined based on the clinical experience of doctors and observation and judgment during the operation.As a result,blood vessels may tear,embolize or narrow again some time after stent implantation.Therefore,it is necessary to carry out preoperative stent implantation simulation analysis according to the vascular characteristics of patients,and use model reconstruction and multi-phase finite element simulation methods such as stent + vessel + blood flow to study the impact of stent implantation on human aortic vessels after the treatment of aortic dissection with covered stent.In view of the present use of the finite element method for the treatment of aortic dissection studies that exist in the 3 d model to vascular structure is too simple,not fully considering the between blood vessels and blood flow to the support of fluid-structure interaction,this article is based on image data of the real cases of vascular model reconstruction,using the finite element method(fem)simulation of coated stent implanted in the aortic dissection and release the dynamic process,to explore the biomechanical characteristics between supports and blood flow,blood vessels,and multiphase flow and solid coupling relationship.In addition,the optimal scaffold structure type was obtained by constructing and simulating the interaction of different scaffold types in blood vessels.The main contents and conclusions of this paper are as follows:1.A finite element simulation process research method suitable for preoperative evaluation of aortic dissection is summarized and proposed.The method is divided into three stages.Based on the real Stanford type B aortic dissection in patients with CT medical image data,using medical image processing software for aortic dissection vascular model to extract the reconstruction and optimization,at the same time,according to the situation of vascular model by using 3 d design software design and build different wave number peak peak peak(5,6 and 8)coated stents model of structural support body,finally the model for grid division;The second stage: stent implantation and finite element simulation of expansion.Finite element analysis software was used to simulate the mechanical properties of the three structures and the implantation and release of the coated stent in aortic dissection.The third stage: multiphase fluid-solid coupling finite element simulation.By extracting the finite element simulation model obtained in the second stage,the multiphase fluid-solid coupling between the scaffold,blood and blood vessels was further analyzed.2.Under compression and grip,the equivalent stress and elastic strain of the support body mainly occur at the bending Angle of the structure.After the implantation of the coated stent,the equivalent stress of the vessel wall is mainly distributed in the area where the stent is in contact.In addition,after the stent implantation,the true vascular lumen squeezed by the prosthesis was re-braced,and the sectional area of the true vascular lumen was significantly increased compared with that before the stent implantation(60.01%?65.53%).In the multiphase fluid-solid coupling analysis of stents,vessels and blood flow,before the stent implantation,the blood flow velocity in the true vascular lumen reached the highest 1.585m/s,and the flow velocity at the entrance of the false lumen reached the highest 1.809m/s.After the stent implantation,the blood flow velocity in the true vascular lumen decreased to 1.125m/s?1.238m/s.Meanwhile,due to the change of flow velocity,the maximum wall pressure in the true cavity increased from 1853 Pa before stent implantation to 2021Pa?2165Pa after stent implantation.In addition has the true lumen of blood vessel walls equivalent stress also reduced significantly,comparing three kinds of stenting after vascular model of fluid-solid coupling analysis result,8 peak type stents blood vessels in the region of the target observation of blood flow velocity is lower than other two,and more close to the human body normal blood flow velocity,at the same time due to the lower velocity of wall pressure is higher than other two peak type stents blood vessels,and in the blood and stents fluid-structure coupling analysis,the equivalent stress mainly distributed in the structure of stent and blood relative positive region,the equivalent stress of 8 peak shape bracket is lower than 5 peak and peak shape bracket,making eight peak shape bracket have better stability within the blood vessels,By comparing the influences of the three kinds of scaffolds on the simulation experiment results,the scaffolds with more crest structures had better improvement effect on the vascular cross section,and the vascular stress distribution was more uniform.In the fluid-solid coupling simulation,the higher the number of crests,the greater the improvement of blood flow velocity in the true lumen.3.The results of finite element simulation show that during the treatment of the coated stent implantation for aortic dissection,the stress after the stent implantation mainly lies in the area in direct contact with the stent.The stent was expanded in place,which could effectively block the false cavity and re-open the true cavity,and the blood flow rate and blood vessel wall pressure in the blood vessels were significantly reduced.By comparing the finite element simulation results of three types of membrane-covered scaffolds with different crest Numbers,such as 5 peak,6 peak and 8 peak,it can be concluded that the 8-peak scaffold is more excellent in improving the flow rate of vessels and the stress of vessel walls. |
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