ObjectiveTo evaluate the value of individualized preoperative simulation in transjugular intrahepatic portosystemic shunt (TIPS).MethodsThin slice scan data of 39 patients with supine upper abdomen were obtained, three dimensional structures of bone, liver, portal vein, inferior vena cava and hepatic vein in CT scan area were reconstructed in Mimics software. According to the size of interventional instruments, a virtual RUPS-100 puncture kit and an VIATORR stent were established in 3D MAX software. Computer simulations were performed to evaluate the route from the hepatic vein puncture portal vein and stent release position. The coincidence of simulation parameters with actual surgical results was compared.Results① The time of preoperative simulation was controllable. The total simulation time was 70–110 minutes (after summing up the previous experience). Preoperative simulation in daily work would not affect the progress of treatment. ② There were 4 cases of puncturing bifurcation of portal vein, 22 cases of puncturing left branch and 13 cases of puncturing right branch during operation (24 cases of puncturing left branch and 15 cases of puncturing right branch by preoperative simulation plan). The overall coincidence rate was 89.7% (35/39). ③ Preoperative simulations were performed using 8 mm×6 cm/2 cm size VIATORR stents, and the stents used in the actual operation were the same as the simulation results. ④ Preoperative simulation and post-operative retrospective simulation could shortened the teaching and training time and enhanced the understanding of surgical intention and key steps.ConclusionPreoperative simulation based on patient's individualized three-dimensional model and virtual interventional device could guided the actual operation of TIPS more accurately, and had practical value for improving the success rate of operation and training young doctors.
One of the main technical challenges when integrating magnetic resonance imaging (MRI) systems with medical linear accelerator is the strong interference of fringe magnetic fields from the MRI system with the electron beams of linear accelerator, making the linear accelerator not to work properly. In order to minimize the interference of magnetic fields, a magnetic shielding cylinder with an open structure made of high permeability materials is designed. ANSYS Maxwell was used to simulate Helmholtz coil which generate uniform magnetic field instead of the fringe magnetic fields which affect accelerator gun. The parameters of shielding tube, such as permeability, radius, length, side thickness, bottom thickness and fringe magnetic fields strength are simulated, and the data is processed by MATLAB to compare the shielding performance. This article gives out a list of magnetic shielding effectiveness with different side thickness and bottom thickness under the optimal radius and length, which showes that this design can meet the shielding requirement for the MRI-linear accelerator system.
The tilted supine position has been evaluated to be one of the significantly effective approaches to prevent bedsore of the patients in the bedridden state. Thus, it has deeply positive influences that in view of dynamics this study explores how the position works. Based on the anatomical theories, this study formulates the human dynamic model. Furthermore, the dynamic simulation of three usual postures in tilted supine position including lying on back, lying with one knee bent and lying with the upper and lower limb on one side lifted is carried out. Therefore, the changes of the three driving forces named as chest force, waist force and thigh force in the tilted supine position can be observed. In order to verify the validity of this simulation, this study obtains the electromyogram measurements of ectopectoralis, external obliques and thigh muscles which are respectively close to the chest, waist and thigh by conducting the human force measurements experiment. The result revealed that in terms of range and trend, the experimental data and simulation’s data were consistent. In conclusion, the changes of these muscles in the supine position movements are researched efficiently by both this experiment and the dynamic simulation. Besides, the result is crucially key to find the mechanism of human’s tilted supine position movements.
Pulse waves contain rich physiological and pathological information of the human vascular system. The pulse wave diagnosis systems are very helpful for the clinical diagnosis and treatment of cardiovascular diseases. Accurate pulse waveform is necessary to evaluate the performances of the pulse wave equipment. However, it is difficult to obtain accurate pulse waveform due to several kinds of physiological and pathological conditions for testing and maintaining the pulse wave acquisition devices. A pulse wave generator was designed and implemented in the present study for this application. The blood flow in the vessel was simulated by modeling the cardiovascular system with windkessel model. Pulse waves can be generated based on the vascular systems with four kinds of resistance. Some functional models such as setting up noise types and signal noise ratio (SNR) values were also added in the designed generator. With the need of portability, high speed dynamic response, scalability and low power consumption for the system, field programmable gate array (FPGA) was chosen as hardware platform, and almost all the works, such as developing an algorithm for pulse waveform and interfacing with memory and liquid crystal display (LCD), were implemented under the flow of system on a programmable chip (SOPC) development. When users input in the key parameters through LCD and touch screen, the corresponding pulse wave will be displayed on the LCD and the desired pulse waveform can be accessed from the analog output channel as well. The structure of the designed pulse wave generator is simple and it can provide accurate solutions for studying and teaching pulse waves and the detection of the equipments for acquisition and diagnosis of pulse wave.
The objective of the mock circulatory system (MCS) is to construct the characteristics of cardiovascular hemodynamics. Westerhof ’s resistor that often regarded as the laminar flow resistance in the MCS, is commonly used to simulate the peripheral resistance of the cardiovascular system. However, the theoretical calculation value of fluid resistance of the Westerhof ’s resistor shows distinguished difference with the actual needed value. If the theoretical resistance is regarded as the actual needed one and be used directly in the experiment, the experimental accuracy would not be acceptable. In order to improve the accuracy, an effective correction method for calculating the resistance of Westerhof ’s resistor was proposed in this paper. Simulation software was also developed to compute accurately the capillary number, total length and resistance. The results demonstrate the proposed method is able to reduce the difficulty and complexity of the design of the resistor, which would obviously increase the manufactured precision of the Westerhof ’s resistor. Simulation software would provide great support to the construction of various MCSs.
Aiming at the problem of scaffold degradation in bone tissue engineering, we studied the feasibility that controlls bone defect repair effect with the inhomogeneous structure of scaffold. The prediction model of bone defect repair which contains governing equations for bone formation and scaffold degradation was constructed on the basis of analyzing the process and main influence factors of bone repair in bone tissue engineering. The process of bone defect repair and bone structure after repairing can be predicted by combining the model with finite element method (FEM). Bone defect repair effects with homogenous and inhomogeneous scaffold were simulated respectively by using the above method. The simulation results illustrated that repair effect could be impacted by scaffold structure obviously and it can also be controlled via the inhomogeneous structure of scaffold with some feasibility.
Sudden cardiac arrest is one of the critical clinical syndromes in emergency situations. A cardiopulmonary resuscitation (CPR) is a necessary curing means for those patients with sudden cardiac arrest. In order to simulate effectively the hemodynamic effects of human under AEI-CPR, which is active compression-decompression CPR coupled with enhanced external counter-pulsation and inspiratory impedance threshold valve, and research physiological parameters of each part of lower limbs in more detail, a CPR simulation model established by Babbs was refined. The part of lower limbs was divided into iliac, thigh and calf, which had 15 physiological parameters. Then, these 15 physiological parameters based on genetic algorithm were optimized, and ideal simulation results were obtained finally.
Computational fluid dynamics was used to investigate the effect of the pathogenesis of membranous obstruction of inferior vena cava of Budd-Chiari syndrome with various angles between right hepatic vein and inferior vena cava. Mimics software was used to reconstruct the models from magnetic resonance imaging (MRI) angiograms of inferior vena cava, right hepatic vein, middle hepatic vein and left hepatic vein, and 3DMAX was used to construct the models of 30°, 60°, 90° and 120° angles between right hepatic vein and inferior vena cava, which was based on the reconstructed models.The model was conducted with clinical parameters in terms of wall shear stress distribution, static pressure distribution and blood velocity. The results demonstrated that the differences between wall shear stress and static pressure had statistical significance with various angles between right hepatic vein and inferior vena cava by SPSS. The pathogenesis of membranous obstruction of inferior vena cava had a correlation with the angles between right hepatic vein and inferior vena cava.
Due to their diverse types, complex causes, high incidence, and difficult treatment, lung diseases have become major killers threatening human life and health, and some lung diseases have a significant impact on alveolar morphology and histology. Numerical simulation of alveolar mechanical response, alveolar flow field information, multiphase flow, and material transport based on computational fluid dynamics is of great significance for lung disease diagnosis, clinical treatment, and in vitro experiments. Starting from the simplification and pathological differences of geometric and mechanical models, this paper analyzes and summarizes the conditions and application scenarios of the airflow dynamics calculation method in pulmonary alveoli, to provide a reference for further simulation and application of the alveolar region.
It is very difficult for stroke patients to complete the action of squatting-standing because their equilibrium function ability has been seriously declined. It was necessary, therefore, to do a deep research on the action of human squatting-standing and to set up an accurate model and simulation. In our modeling research, the movements of upper limbs and head was neglected, and a seven-segment model was developed to establish the coordinate system of human squatting-standing action. It calculated the knee joint moment and hip joint moment during squatting and standing by utilizing Lagrange method, and then simulated this mathematical model by utilizing Matlab. Geometric model of human squatting-standing was developed and simulated in ADAMS which proved that the established Lagrange model was reasonable. It would also provide significant theoretical references for further study and development of squatting-standing rehabilitation training equipment.