Structure Design and Finite Element Analysis on Patch in Intraventricular Tunnel / 医用生物力学

ObjectiveT o explore the influence of patch shape for intraventricular tunnel (IVT) construction on biomechanical performance of the double outlet right ventricle after correction. Methods Based on the idealized IVT model, a two-dimensional IVT patch was designed. Six groups of patch models with the rhombic long-to-short axis ratio of 1∶0.625, 1∶0.3, 1∶0.2, 1∶0.15, 1∶0.125, 1∶0.1 were established according to the difference between the long and short axis of the rhombus patch in the turning part, and finite element analysis method was used to numerically simulate the process of stitching, holding and propping up the patch into a three-dimensional (3D) IVT model. Results The maximum stresses on suture line of 6 patch models were mainly concentrated at acute-angle corners of the rhombus. As rhombic long-to-short axis ratio of the patch increased, the maximum stress of the IVT suture line first decreased and then increased, and the volume showed an increasing trend. The pressure difference between two ends of the tunnel first decreased and then increased. The patch with the long-to-short axis ratio of 1∶0.15 had a uniform surface stress distribution, and the maximum stress on the suture line was the smallest. Meanwhile the right ventricular volume was less encroached on, and the pressure difference at both ends of the tunnel was small. Conclusions The IVT shape can influence stresses of suture line, the right ventricle volume and the pressure difference of IVT with non-monotonic variations. The suture effect of the patch with the long-to-short axis ratio of 1∶0.15 is relatively better among the constructed models.

Numerical Analysis on Adaptability of Valve Leaflets after Single Valve Replacement in Children / 医用生物力学

Objective To explore the biomechanical mechanism of aortic insufficiency (AI) after single aortic valve replacement (SAVR) in children and propose the corresponding countermeasures. Methods The idealized aortic valve model and postoperative growth model were constructed. By changing the length of leaflet free edge, leaflet height as well as improving the design with a concave structure, the effects of different structure dimensions on movement synchronization and closing performance of the aortic valve after surgery were compared. Results The closure of the replacement leaflet lagged behind the autologous leaflet, which fitted 2 mm below free edge of the replacement leaflet. AI occurred 6 years after operation. Increasing leaflet height could not improve the postoperative effect and would increase the maximum stress of the leaflet. Increasing free edge length by 10% could improve the postoperative outcomes, while increasing free edge length by 15% would cause the leaflet to be too long, hence resulting in a poor fit of the aortic valve. Compared with the traditional structure, the concave structure was more beneficial for closing performance of the aortic valve, and it could effectively reduce the maximum stress by 20% with the best effect. Conclusions The leaflet movement will be out of synchronization after SAVR, the point of convergence will be shifted, and AI will appear 6 years after surgery. It is recommended to use a concave structure with free edge length increased by 10%, while increasing leaflet height is not recommended.

Structural design and biomechanical numerical analysis of body-fitted stent in stenotic vessels / 生物医学工程学杂志

To solve the problem of stent malapposition of intravascular stents, explore the design method of intravascular body-fitted stent structure and to establish an objective apposition evaluation method, the support and apposition performance of body-fitted stent in the stenotic vessels with different degrees of calcified plaque were simulated and analyzed. The traditional tube-mesh-like stent model was constructed by using computational aided design tool SolidWorks, and based on this model, the body-fitted stent model was designed by means of projection algorithm. Abaqus was used to simulate the crimping-expansion-recoil process of the two stents in the stenotic vessel with incompletely calcified plaque and completely calcified plaque respectively. A comprehensive method for apposition evaluation was proposed considering three aspects such as separation distance, fraction of non-contact area and residual volume. Compared with the traditional stent, the separation distances of the body-fitted stent in the incompletely calcified plaque model and the completely calcified plaque model were decreased by 21.5% and 22.0% respectively, the fractions of non-contact areas were decreased by 11.3% and 11.1% respectively, and the residual volumes were decreased by 93.1% and 92.5% respectively. The body-fitted stent improved the apposition performance and was effective in both incompletely and completely calcified plaque models. The established apposition performance evaluation method of stent considered more geometric factors, and the results were more comprehensive and objective.

Numerical Simulation of Fractional Flow Reserve Based on Shape Resistance of Coronary Artery / 医用生物力学

Objective To establish a method for non-invasive calculation of fractional flow reserve (FFRCT) with the shape resistance of coronary artery stenosis as boundary condition, and to verify the accuracy of this method. Methods CT angiography images of 16 patients with coronary artery disease were reconstructed; the mathematical model of shape resistance was established by considering the minimum cross-sectional area and the length of stenosis of coronary artery stenosis, the induced pressure difference as the boundary condition was applied to calculate FFRCT (named as shape resistance method ). The values of clinical FFR were taken as the gold standard, previous diameter method and volume method were taken as control method, and accuracy of shape resistance method was investigated from the aspects of mean error rate, accuracy rate, sensitivity rate, positive prediction rate and negative prediction rate. Results The mean error rate of calculated FFRCT by the diameter method, volume method and shape resistance method were 11.76%, 10.46%, 4.82%, the accuracy rates were 85%, 65%, 90%, the sensitivity rates were 87.5%, 66.7%, 87.5%, the positive prediction rate were 75%, 25%, 87.5%, respectively, while the negative prediction rates were all 91.6%. Conclusions The established shape resistance method is better than the diameter method and volume method from the aspects of mean error rate, accuracy rate, sensitivity rate and positive prediction rate; the FFRCT based on the shape resistance method and clinical FFR have good consistency, and this work may provide a new way for the calculation and application of FFRCT.

Review of studies on the biomechanical modelling of the coupling effect between stent degradation and blood vessel remodeling / 生物医学工程学杂志

The dynamic coupling of stent degradation and vessel remodeling can influence not only the structural morphology and material property of stent and vessel, but also the development of in-stent restenosis. The research achievements of biomechanical modelling and analysis of stent degradation and vessel remodeling were reviewed; several noteworthy research perspectives were addressed, a stent-vessel coupling model was developed based on stent damage function and vessel growth function, and then concepts of matching ratio and risk factor were established so as to evaluate the treatment effect of stent intervention, which may lay the scientific foundation for the structure design, mechanical analysis and clinical application of biodegradable stent.

Structure Design and Mechanical Analysis of a Novel Biodegradable Zinc Alloy Stent / 医用生物力学

Objective To compare and analyze the mechanical performance of a new biodegradable stent and a common stent and their effects on treating the stenotic vessels. Methods Using finite numerical simulation, the new stent and the common stent were implanted into vessels with a diameter stenosis of 30%, and their support performance and influences on reshaping the stenotic vessels were investigated. Results The radial recoiling ratio and dog-boning ratio of the new stent were decreased by 26.6% and 34.7%, respectively, compared with the common stent. Besides, the stenotic vessel deployed with the new stent recoiled less and had a flatter and larger lumen. Conclusions Compared with the common stent, the new stent has stronger scaffold performance and a better therapeutic effect on stenotic vessels. The new stent with stronger scaffold performance is highly expected to be an alternative choice in interventional surgeries.

Influence of valve height on the opening/closure performance of transplanted aortic valve / 生物医学工程学杂志

Valve transplantation is often used in the treatment of aortic valve insufficiency. However, after surgery, the reconstructed aortic roots have an expansion phenomenon, in which the lack of valve height causes the aortic valve to close again. In this paper, the effects of different aortic valve height design on valve opening and closing performance were studied. The optimal surgical plan was obtained by numerical simulation, providing technical support and theoretical basis. In this paper, six groups of three-dimensional geometric models with a valve height increment of ± 0.5 mm were established with a root diameter of 26.0 mm and a valve height of 14.0 mm. Through the structural mechanics calculation and analysis of the parameters such as maximum stress, valve area and contact force of the model, reasonable geometrical dimensions are obtained. The study found that the maximum stress values of the six groups of models ranged from 640 to 690 kPa, which was consistent with the results of the literature; the three-group models with valve heights of 13.5 mm, 14.0 mm, and 14.5 mm were within a reasonable range. The contact force value of the 6 groups of leaflets increased with the increase of valve height. Studies have shown that the height of the aortic valve has an effect on the aortic valve closure performance. A valve height that is too small or too large will reduce the aortic systolic valve area and affect the aortic function.

Research on the cardiovascular function evaluation system based on noninvasive detection indices / 生物医学工程学杂志

Based on the noninvasive detection indeices and fuzzy mathematics method, this paper studied the noninvasive, convenient and economical cardiovascular health assessment system. The health evaluation index of cardiovascular function was built based on the internationally recognized risk factors of cardiovascular disease and the noninvasive detection index. The weight of 12 indexes was completed by the analytic hierarchy process, and the consistency test was passed. The membership function, evaluation matrix and evaluation model were built by fuzzy mathematics. The introducted methods enhanced the scientificity of the evaluation system. Through the Kappa consistency test, McNemer statistical results ( = 0.995 > 0.05) and Kappa values (Kappa = 0.616, < 0.001) suggest that the comprehensive evaluation results of model in this paper are relatively consistent with the clinical, which is of certain scientific significance for the early detection of cardiovascular diseases.

Effect of sinus diameter on the opening and closing performance of aortic valve under the expansion of aortic root / 生物医学工程学杂志

This study aims to explore the effect of aortic sinus diameter on aortic valve opening and closing performance in the case of no obvious disease of aortic valve and annulus and continuous dilation of aortic root. A total of 25 three-dimensional aortic root models with different aortic sinus and root diameters were constructed according to the size of clinical surgical guidance. The valve sinus diameter S is set to 32, 36, 40, 44 and 48 mm, respectively, and the aortic root diameter is set to 26, 27, 28, 29 and 30 mm, respectively. Through the structural mechanics calculation with the finite element software, the maximum stress, valve orifice area, contact force and other parameters of the model are analyzed to evaluate the valve opening and closing performance under the dilated state. The study found that aortic valve stenosis occurs when the = 32 mm, = 26, 27 mm and = 36 mm, = 26 mm. Aortic regurgitation occurs when the = 32, 36 and 40 mm, = 30 mm and = 44, 48 mm, = 29, 30 mm. The other 15 models had normal valve movement. The results showed that the size of the aortic sinus affected the opening and closing performance of the aortic valve. The smaller sinus diameter adapted with the larger root diameter and the larger sinus diameter adapted with the smaller root diameter. When the sinus diameter is 40 mm, the mechanical performance of the valve are good and it can well adapt with the relatively large range of aortic root dilation.

Numerical simulation of the effect of virtual stent release pose on the expansion results / 生物医学工程学杂志

The current finite element analysis of vascular stent expansion does not take into account the effect of the stent release pose on the expansion results. In this study, stent and vessel model were established by Pro/E. Five kinds of finite element assembly models were constructed by ABAQUS, including 0 degree without eccentricity model, 3 degree without eccentricity model, 5 degree without eccentricity model, 0 degree axial eccentricity model and 0 degree radial eccentricity model. These models were divided into two groups of experiments for numerical simulation with respect to angle and eccentricity. The mechanical parameters such as foreshortening rate, radial recoil rate and dog boning rate were calculated. The influence of angle and eccentricity on the numerical simulation was obtained by comparative analysis. Calculation results showed that the residual stenosis rates were 38.3%, 38.4%, 38.4%, 35.7% and 38.2% respectively for the 5 models. The results indicate that the pose has less effect on the numerical simulation results so that it can be neglected when the accuracy of the result is not highly required, and the basic model as 0 degree without eccentricity model is feasible for numerical simulation.

Noninvasive numerical simulation of coronary fractional flow reserve based on lattice Boltzmann method / 生物医学工程学杂志

In order to investigate the application of lattice Boltzmann method (LBM) in the numerical simulation of computed tomography angiography-derived fractional flow reserve (FFR ), an idealized narrowed tube model and two coronary stenosis arterymodels are studied. Based on the open source code library (Palabos), the relative algorithm program in the development environment (Codeblocks) was improved. Through comparing and analyzing the results of FFR which is simulated by LBM and finite element analysis software ANSYS, and the feasibility of the numerical simulation of FFR by LBM was verified . The results show that the relative error between the results of LBM and finite element analysis software ANSYS is about 1%, which vertifies the feasibility of simulating the coronary FFR by LBM. The simulation of this study provides technical support for developing future FFR application software, and lays the foundation for the calculation of clinical FFR .

Establishment and assessment of chronic coronary stenosis model for fractional flow reserve derived from coronary CT angiography in Bama miniature pig / 中国医学影像技术

Objective To establish chronic coronary stenosis model for fractional flow reserve derived from coronary CT angiography (FFRcT) in Bama miniature pig,and to evaluate its reliability.Methods Sixteen Bama miniature pigs were used to establish chronic coronary stenosis models through placing Ameroid constrictor into proximal or middle segments of left anterior descending arteries (LAD).In the 2nd week after modeling,the degrees of stenosis were monitored with coronary CTA.Invasive coronary angiography was used to verify stenosis degrees and measure fractional flow reserve (FFR) within 2 days of last coronary CTA examination.Computational fluid dynamics model was constructed and FFRcT was calculated by the specialized laboratory based on coronary CTA data respectively.Simulated FFRcT and FFR values were compared to verify this model.Results Models were successfully established in 10 pigs with a total of 24 coronary CT examinations,of which image quality met the diagnostic requirements.All models were with LAD stenosis＜25 ％ in the 2nd week after operation.LAD stenosis ＞50％ was found in the 3rd week in 9 pigs,and the other one was found with LAD stenosis ＞50％ in the 4th week.The results of coronary CTA corresponded to those of coronary angiography.There was no significant difference between simulated FFRcT and FFR value (t =-1.13,P =0.29).Conclusion Through placing Ameroid constrictor into LAD of Bama miniature pig and monitoring the degree of stenosis with coronary CTA,model of chronic coronary stenosis could be successfully established,which are suitable for noninvasive simulating hemodynamics study based on coronary CTA.

Finite Element Analysis on Partially Closed and Fully Opened Aortic Valve / 医用生物力学

Objective To explore the effect of different initial state setting on a valve simulation. Methods Two-dimensional structural models were established with the initial state of the aortic valve being partially closed in one model and fully opened in the other. The time-dependent load was applied to the valve and the vessel wall of the aortic and the ventricle sides. The finite element method was used to study the maximum stress, the length of the joint, and the contact force of the closed aortic valve under two different initial states. Results The stress and contact force of the aortic valve were relatively large at the closed position when the initial state was fully opened. The closure degree of the valve was low, and the variations in stress and closure degree were large during the periodic cycle. The stress and contact force of the valve were relatively small when the aortic valve was partially closed. The closure degree was high, and the variations in stress and closure degree of the aortic valve were small during the periodic cycle. Conclusions In the case of the aortic valve partially closed in the initial state, the stability of the calculation process and the closure degree of the valve were relatively high, which should be given more consideration in numerical simulation. The results can be used to study the mechanical behavior of the valve and the biomechanical mechanism of the aortic root.

Numerical simulation of fluid-structure interaction in fusiform aneurysm treated with stent with triangular wire cross-section / 生物医学工程学杂志

A new stent with triangular wire cross-section was proposed. The new stents were compared with traditional circular wire cross-section stent in the same porosity in order to investigate its effectiveness in treating intracranial aneurysms. Three models were established separately, including the aneurysm model with circle cross section stent, the aneurysm model with triangular cross section stent and the aneurysm model with non-stent. Then the same boundary conditions were set to contrast the resistance to flow, velocity, pressure, wall shear stress and total mesh displacement. The resistance to flow of triangular cross section stent was lower than circle cross section stent and the velocity, pressure, total mesh displacement of aneurysm model with triangular cross section stent were all higher than those of the model with circle cross section stent. Moreover, the peak value and valley value of wall shear stress in aneurysm model with triangular cross section stent were higher than those of the other. Triangular cross section stent might play a negative role to aneurysm rupturing. Thus, the therapeutic effect of stent with triangle cross section was not better than the stent with circle cross section. In the clinical application, doctors should consider the various factors, and choose the most suitable one.

Numerical simulation research of the triangular cross-section structure flow resistance in endovascular stent / 中国组织工程研究

To provide a reference basis for the structural design and optimization of endovascular stent by analyzing the flow resistance of the new stent with triangle cross-section using numerical simulation method, and finding out the stent structure which will influence hemodynamic parameters. Four kinds of models of the triangle cross-section bare stent were constructed in infinite flow field using solidworks software. Numerical simulations of the four models were performed respectively using ANSYS finite element software. Steady flows and transient flows in these models were studied. Hemodynamics data in the four models were collected, such as the flow patterns, the distribution of pressure and the flow resistance of the new stents. The stent with triangular wire cross-section can be applied to cover aneurysm cavity because that resistance of blood inflow to aneurysm was large and outflow from aneurysm was small. Thus, it was easy to outflow than inflow. Thereby blood perfusion and flow of aneurysm cavity was restrained, and the pressure of aneurysm cavity was reduced, which plays a certain effect on the treatment of aneurysm. This result provides some instructions for the design of stent structure.

Numerical simulation of semi-circular section stent grafts / 中国组织工程研究

Geometrically virtual models of three-dimensional blood flow field and eight types of mesh stent (different porosity and different stent shape) were constructed using SoildWorks software, and simulation of stented models were performed respectively using finite element software ANSYS11.0 according to computation fluid dynamics method. The flow resistance of the semi-circular section stent model of blood flow from the semi-circular planar surface was greater than the reverse in a certain range of permeability. However, the result was the opposite when the porosity increased to a specific value. For both grid-stent model and sine-stent model, flow resistance of blood that flowed from the stent in both directions increased with the porosity reduction. Under the same porosity and the direction of blood flow from the same stent, the flow resistance of the grid stent model was 1.5 times greater than the sine-stent model. Results showed that there are different effects on the flow resistance in blood flow in different directions from the semi-circular section stent model.

Numerical simulation of treating aortic dissection using artery-abdominal aorta bypass graft / 中国组织工程研究

Aortic dissection is a common disease which is very dangerous,with high mortality rate.Bypass graft for the treatment of DeBakey Ⅲ dissection has outstanding advantages than the ordinary replacement of thoracic aorta,and some patients will inevitably require the use of the procedure.The purpose of this study was to explore the impact of the subclavian artery-abdominal aorta bypass graft on hemodynamic parameters in the false lumen and the effectiveness of surgical treatment.First of all,the idealized three-dimensional geometric models of DeBakey Ⅲ aortic dissection and its subclavian artery-abdominal aorta bypass graft operation were constructed,respectively.Then the models were imported into ANSYS 11.0 for finite element analysis.Results of numerical simulation showed that both velocity and pressure of the blood flow were reduced after bypass graft at the entrance and in the internal sac of false lumen,which is very favorable for reducing the impact of blood flow on false lumen,slowing down the further expansion of entrance,preventing the breakdown of false lumen,and promoting the healing of dissection.Therefore,the subclavian artery-abdominal aorta bypass graft operation is an effective surgical method for the treatment of DeBakey Ⅲ aortic dissection in some particular cases.This operation is with great prospects for clinical application.

Progress of basod on hemodynamics simulation cardiovascular Surgical planning / 医用生物力学

Hemodynamics-simulation-based cardiovascular surgical planning.which is the patient-specific surgical hemodynamics optimization based on medical image,is the further development of clinical-applica-tion-oriented computational hemodynamics,it is very helpful for cardiovascular surgical decision-making.The art-in-work of hemodynamics-simulation-based cardiovascular surgical planning in both domestic and over-seas research was reviewed,the key problems and solutions involved were analyzed,and the further develo-ping objectives were presented.

Influences of graft diameter on the blood flow in 2-way bypassing surgery / 生物医学工程学杂志

The graft diameter plays a critically important role in the long-term patency rates of bypass surgery. To clarify the influence of graft diameter on the blood flows in the femoral 2-way bypass surgery, the physiologically pulsatile flows in two femoral bypass models were simulated with numerical methods. For the sake of comparison, the models were constructed with identical geometry parameters except the different diameters of grafts. Two models with small and large grafts were studied. The boundary conditions for the simulation of blood flow were constant for both models. The maximum Reynolds number was 832.8, and the Womersley number was 6.14. The emphases of results were on the analysis of flow fields in the vicinity of the distal anastomosis. The temporal-spatial distributions of velocity vectors, pressure drop between the proximal and distal toe, wall shear stresses, wall shear stress gradients and oscillating shear index were compared. The present study indicated that femoral artery bypassed with a large graft demonstrated disturbed axial flow and secondary flow at the distal anastomosis while the axial flow at its downstream of toe was featured with larger and more uniform longitudinal velocities. Meanwhile, the large model exhibits less refluences, relatively uniform wall shear stresses, lower pressure and smaller wall shear stress gradients, whereas it does not have any advantages in the distributions of secondary flow and the oscillating shear index. In general, the large model exhibits better and more uniform hemodynamic phenomena near the vessel wall and may be effective in preventing the initiation and development of postoperative intimal hyperplasia and restenosis.

Simulation of stent treatment for aneurysms in the inner bend of aortic arch / 生物医学工程学杂志

Endovascular stent is a new technique for the treatment of aortic arch aneurysms. The present simulation study of endovascular stent treatment for aneurysms in the inner bend of aortic arch is initiated by the fact that no one has ever investigated the hemodynamics of stented aortic arch aneurysm harboring a bleb. For the comparative convenience, a stented and a nonstented aortic arch aneurysm models were constructed respectively. Physiological blood flows in both models were simulated using the computational fluid dynamics method. The detailed flow patterns, pressure and wall shear stress distributions around the aneurysm of both models were compared and analyzed so as to evaluate the effectiveness of endovascular stent treatment for aortic arch aneurysms. Results showed that the stented model is attributed to substantially different intra-aneurysmal flow patterns versus the nonstented model. Flow activities within the stented aneurysmal sacs are markedly diminished, specifically the pressure and wall shear stress in the bleb were significantly decreased. These phenomena allow us to conclude that endovascular stent can promote intra-aneurysmal thrombus development and attenuating aneurysm rupture risk.