Objective To investigate the effects of different types of tricuspid regurgitation, implantation positions, and device models on the treatment outcomes of K-Clip for tricuspid regurgitation using numerical simulations. Methods Three-dimensional reconstruction of the heart model was performed based on CT images. Two different regurgitation orifices were obtained by modifying the standard parameterized tricuspid valve leaflets and chordae tendineae. The effects of different K-Clip models at different implantation positions (posterior leaflet midpoint, anterior-posterior commissure, anterior leaflet midpoint, posterior septal commissure) were simulated using commercial explicit dynamics software Ls-Dyna. Conclusion For the two types of regurgitation in this study, clipping at the posterior leaflet midpoint resulted in a better reduction of the regurgitation orifice (up to 75% reduction in area). Higher clamping forces were required for implantation at the anterior leaflet midpoint and posterior septal commissure, which was unfavorable for the smooth closure of the clipping components. There was no statistical difference in the treatment outcomes between the 18T and 16T K-Clip components, and the 16T component required less clamping force. Therefore, the use of the 16T K-Clip component is recommended.
In order to investigate the application of lattice Boltzmann method (LBM) in the numerical simulation of computed tomography angiography-derived fractional flow reserve (FFRCT), 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 FFRCT which is simulated by LBM and finite element analysis software ANSYS, and the feasibility of the numerical simulation of FFRCT 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 FFRCT by LBM. The simulation of this study provides technical support for developing future FFRCT application software, and lays the foundation for the calculation of clinical FFRCT.
The high rotational speed of the axial flow blood pump and flow separation of the centrifugal blood pump are the main causes for blood damage in blood pump. The mixed flow blood pump can effectively alleviate the high rotational speed and the flow separation. Based on this, the purpose of this study is to explore the performance of the mixed blood pump with a closed impeller. A mixed flow blood pump with closed impeller was studied by numerical simulation in this paper. The flow field characteristics and the pressure distribution of this type of blood pump were analyzed. The hydraulic performance of the blood pump and the possible damages to red blood cells were also discussed. At last, pump performance was compared with the mixed flow blood pump with semi-open impeller. The results show that the mixed flow blood pump with close impeller studied in this paper can operate safely and efficiently with a good performance. The pump can reach the pressure head of 100 mmHg at 5 L/min mass flow rate. Flow in the blood pump is uniform and no obvious separation or vortex occurs. Pressure distribution in and on the impeller is uniform and reasonable, which can effectively avoid the thrombosis of blood. The average mean value of hemolysis index is 4.99 × 10−4. The pump has a good biocompatibility. Compared with the mixed flow blood pump with semi-open impeller, the mixed flow blood pump with closed impeller has higher head and efficiency, a smaller mean value of hemolysis index prediction, a better hydraulic performance and the ability to avoid blood damage. The results of this study may provide a basis for the performance evaluation of the closed impeller mixed flow blood pump.
The inhalation and deposition of particles in human pulmonary acinus region can cause lung diseases. Numerical simulation of the deposition of inhaled particles in the pulmonary acinus region has offered an effective gateway to the prevention and clinical treatment of these diseases. Based on some important affecting factors such as pulmonary acinar models, model motion, breathing patterns, particulate characteristics, lung diseases and ages, the present research results of numerical simulation in human pulmonary acinus region were summarized and analyzed, and the future development directions were put forward in this paper, providing new insights into the further research and application of the numerical simulation in the pulmonary acinus region.
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.
A three-dimensional (3D) model of human anterior chamber is reconstructed to explore the effect of different corneal temperatures on the heat transfer in the chamber. Based on the optical coherence tomography imaging of the volunteers with normal anterior chamber, a 3D anterior chamber model was reconstructed by the method of UG parametric design. Numerical simulation of heat transfer and aqueous humor flow in the whole anterior chamber were analyzed by the finite volume methods at different corneal temperatures. The results showed that different corneal temperatures had obvious influence on the temperature distribution and the aqueous flow in the anterior chamber. The temperature distribution is linear and axial symmetrical around the pupillary axis. As the temperature difference increases, the symmetry becomes poorer. Aqueous floated along the warm side and sank along the cool side which forms a vortexing flow. Its velocity increased with the addition of temperature difference. Heat fluxes of cornea, lens andiris were mainly affected by the aqueous velocity. The higher the velocity, the bigger more absolute value of the above-mentioned heat fluxes became. It is practicable to perform the numerical simulation of anterior chamber by the optical coherence tomography imaging. The results are useful for studying the important effect of corneal temperature on the heat transfer and aqueous humor dynamics in the anterior chamber.
A solid-liquid two-phase finite element model of articular cartilage and a microscopic finite element model of chondrocytes were established using the finite element software COMSOL in this study. The purpose of the study is to investigate the mechanics environment and the liquid flow field of the host cartilage chondrocytes in each layer by multi-scale method, under physiological load, with the different elastic modulus of artificial cartilage to repair cartilage defect. The simulation results showed that the uniform elastic modulus of artificial cartilage had different influences on the microenvironment of different layer chondrocytes. With the increase of the elastic modulus of artificial cartilage, the stress of the shallow surface layer and the intermediate layer chondrocytes increased and the stress of deep layer chondrocytes decreased. The flow field direction of the middle layer and the bottom layer of cartilage can also be changed by artificial cartilage implantation, as well as the ways of nourishment supply of the middle layer and underlying chondrocytes change. A barrier to underlying chondrocytes nutrition supply may be caused by this, thus resulting in the uncertainty of the repair results. With cross-scale finite element model simulation analysis of chondrocytes, we can quantitatively evaluate the mechanical environment of chondrocytes in each layer of the host cartilage. It is helpful to assess the clinical effect of cartilage defect reparation more accurately.
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.
Inhalable particles deposition in the human respiratory system is the main cause of many respiratory and cardiovascular diseases. It plays an important role in related disease prevention and treatment through establishing computer or external entity models to study rules of particle deposition. The paper summarized and analyzed the present research results of various inhalable particle deposition models of upper respiratory tract and pulmonary area, and expounded the application in the areas of disease inducement analysis, drug inhale treatment etc. Based on the review, the paper puts forward the problems and application limitations of present research, especially pointing out future emphasis in development directions. It will have a value of reference guidance for further systematic and in-depth study on the inhalable particle deposition simulation, experiment and application.
The implantable miniaturized axial blood pump works at a high rotational speed, which increases the risk of blood damage. In this article, we aimed to reduce the possibility of hemolysis and thrombosis by designing a two-stage axial blood pump. Under the operation conditions of flow rate 5 L/min and outlet pressure of 100 mm Hg, we carried out the numerical simulation on the two-stage and single-stage blood pumps to compare the hemolysis and platelet activation state. The results turned out that the hemolysis index of two-stage axial blood pump was better while the platelet activation state was worse than those of single stage design. On the index of hemolysis level and platelet activation state, the design of the two-stage pump with the low and high-head impeller combination was better than the two-stage pump with the equal heads, or the high and low-head impeller combination. In terms of reducing the risk of blood damage for implantable miniaturized axial blood pump, the research result can provide some theoretical basis and new design ideas.