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.
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.
Objective To explore the effectiveness and predictive value of computer simulated thoracic endovascular aortic repair (TEVAR). Methods The clinical data of the patients with Stanford type B aortic dissection who underwent TEVAR from February 2019 to February 2022 in our hospital was collected. According to whether there was residual false cavity around the stent about 1 week after TEVAR, the patients were divided into a false cavity closure group and a false cavity residual group. Based on computer simulation, personalized design and three-dimensional construction of the stent framework and covering were carried out. After the stent framework and membrane were assembled, they were pressed and placed into the reconstructed aortic dissection model. TEVAR computer simulation was performed, and the simulation results were analyzed for hemodynamics to obtain the maximum blood flow velocity and maximum wall shear stress at the false lumen outlet level at the peak systolic velocity of the ventricle, which were compared with the real hemodynamic data of the patient after TEVAR surgery. The impact of hemodynamics on the residual false lumen around the stent in the near future based on computer simulation of hemodynamic data after TEVAR surgery was further explored. Results Finally a total of 28 patients were collected, including 24 males and 4 females aged 53.390±11.020 years. There were 18 patients in the false cavity closure group, and 10 patients in the false cavity residual group. The error rate of shear stress of the distal decompression port of the false cavity after computer simulation TEVAR was 6%-25%, and the error rate of blood flow velocity was 3%-31%. There was no statistical difference in age, proportion of male, history of hypertension, history of diabetes, smoking history, prothrombin time or activated partial thromboplatin time at admission between the two groups (all P>0.05). The blood flow velocity and shear stress after TEVAR were statistically significant (all P<0.05). The maximum shear stress (OR=1.823, P=0.010) of the false cavity at the level of the distal decompression port after simulated TEVAR was an independent risk factor for the residual false cavity around the stent. Receiver operating characteristic curve analysis showed that the area under the curve corresponding to the maximum shear stress of false cavity at the level of distal decompression port after simulated TEVAR was 0.872, the best cross-sectional value was 8.469 Pa, and the sensitivity and specificity were 90.0% and 83.3%, respectively. Conclusion Computers can effectively simulate TEVAR and perform hemodynamic analysis before and after TEVAR surgery through simulation. Maximum shear stress at the decompression port of the distal end of the false cavity is an independent risk factor for the residual false cavity around the stent. When it is greater than 8.469 Pa, the probability of residual false cavity around the stent increases greatly.
The mechanical behavior modeling of human soft biological tissues is a key issue for a large number of medical applications, such as surgery simulation, surgery planning, diagnosis, etc. To develop a biomechanical model of human soft tissues under large deformation for surgery simulation, the adaptive quasi-linear viscoelastic (AQLV) model was proposed and applied in human forearm soft tissues by indentation tests. An incremental ramp-and-hold test was carried out to calibrate the model parameters. To verify the predictive ability of the AQLV model, the incremental ramp-and-hold test, a single large amplitude ramp-and-hold test and a sinusoidal cyclic test at large strain amplitude were adopted in this study. Results showed that the AQLV model could predict the test results under the three kinds of load conditions. It is concluded that the AQLV model is feasible to describe the nonlinear viscoelastic properties of in vivo soft tissues under large deformation. It is promising that this model can be selected as one of the soft tissues models in the software design for surgery simulation or diagnosis.
A method of ultrasonic simulation based on the FIELD II software platform for carotid artery plaque was proposed according to the analysis for geometrical shape, tissue characteristics and acoustic properties of carotid artery plaques in clinic, and then a simulation system was developed by using the MATLAB graphical user interface (GUI). In the simulation and development, a three-dimensional geometric model of blood vessel with plaques was set up by using the metaball implicit surface technique, and a tissue model was established based on the scatterers with spatial position of gamma random distribution. Comparison of the statistical and geometrical characteristics from simulated ultrasound B-mode images with those based on clinical ones and preset values, the results fully demonstrated the effectiveness of the simulation methods and system.
Tumor-treating fields (TTFields) is a novel treatment modality for malignant solid tumors, often employing electric field simulations to analyze the distribution of electric fields on the tumor under different parameters of TTFields. Due to the present difficulties and high costs associated with reproducing or implementing the simulation model construction techniques, this study used readily available open-source software tools to construct a highly accurate, easily implementable finite element simulation model for TTFields. The accuracy of the model is at a level of 1 mm3. Using this simulation model, the study carried out analyses of different factors, such as tissue electrical parameters and electrode configurations. The results show that factors influncing the distribution of the internal electric field of the tumor include changes in scalp and skull conductivity (with a maximum variation of 21.0% in the treatment field of the tumor), changes in tumor conductivity (with a maximum variation of 157.8% in the treatment field of the tumor), and different electrode positions and combinations (with a maximum variation of 74.2% in the treatment field of the tumor). In summary, the results of this study validate the feasibility and effectiveness of the proposed modeling method, which can provide an important reference for future simulation analyses of TTFields and clinical applications.
With the post-disaster psychological crisis has aroused wide attention, psychological first aid which can relieve psychological trauma and prevent post-traumatic disorder has been valued by many countries. However, mainly domestic psychological first aid training is simply theoretical training while its popularizing rate is low, it is urgent to learn from international experience to carry out more effective psychological first aid training. In the context of combination of medicine and industry, the paper majorly embodied virtual simulation’s potential in improving psychological intervention ability, deep learning level and self-efficacy. Furthermore, the paper analyzed and illustrated theoretical basis and function module of constructing psychological first aid training platform in detail, and prospected further improvement, which laid foundations for follow-up studies.
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.