目的 探讨CT仿真内镜（CT virtual endoscopy，CTVE）在低位直肠癌术前分期中的价值。方法 收集我院2008年8月1日至2011年3月1日期间的直肠癌患者57例，术前行直肠CTVE检查，详细记录患者直肠癌周围组织浸润和淋巴结转移的情况；患者术后常规进行病理检查，比较两者结果的差异。结果 术前直肠CTVE检查与术后石蜡病理检查对直肠癌周围淋巴结转移的判断经四格表χ2检验，差异无统计学意义（χ2=2.5，P＞0.05），其对直肠癌周围淋巴结转移预测的敏感性为66.67%，特异性为93.94%。术前直肠CTVE预测直肠癌周围组织浸润和术后病理检查结果经四格表χ2检验，差异有统计学意义（χ2=4.4，P＜0.05），其对直肠癌周围组织浸润判断的敏感性为27.78%，特异性为42.86%。结论 CTVE在术前评估直肠癌周围淋巴结转移有较高的可信性，但对直肠癌周围组织浸润的评价较差。
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 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.
The rotation center of traditional hip disarticulation prosthesis is often placed in the front and lower part of the socket, which is asymmetric with the rotation center of the healthy hip joint, resulting in poor symmetry between the prosthesis movement and the healthy lower limb movement. Besides, most of the prosthesis are passive joints, which need to rely on the amputee’s compensatory hip lifting movement to realize the prosthesis movement, and the same walking movement needs to consume 2–3 times of energy compared with normal people. This paper presents a dynamic hip disarticulation prosthesis (HDPs) based on remote center of mechanism (RCM). Using the double parallelogram design method, taking the minimum size of the mechanism as the objective, the genetic algorithm was used to optimize the size, and the rotation center of the prosthesis was symmetrical with the rotation center of the healthy lower limb. By analyzing the relationship between the torque and angle of hip joint in the process of human walking, the control system mirrored the motion parameters of the lower on the healthy side, and used the parallel drive system to provide assistance for the prosthesis. Based on the established virtual prototype simulation platform of solid works and Adams, the motion simulation of hip disarticulation prosthesis was carried out and the change curve was obtained. Through quantitative comparison with healthy lower limb and traditional prosthesis, the scientificity of the design scheme was analyzed. The results show that the design can achieve the desired effect, and the design scheme is feasible.
The pulse amplitude of fingertip volume could be improved by selecting the vascular dense area and applying appropriate pressure above it. In view of this phenomenon, this paper used Comsol Multiphysics 5.6 (Comsol, Sweden), the finite element analysis software of multi-physical field coupling simulation, to establish the vascular tissue model of a single small artery in fingertips for simulation. Three dimensional Navier-Stokes equations were solved by finite element method, the velocity field and pressure distribution of blood were calculated, and the deformation of blood vessels and surrounding tissues was analyzed. Based on Lambert Beer's Law, the influence of the longitudinal compression displacement of the lateral light surface region and the tissue model on the light intensity signal is investigated. The results show that the light intensity signal amplitude could be increased and its peak value could be reduced by selecting the area with dense blood vessels. Applying deep pressure to the tissue increased the amplitude and peak of the signal. It is expected that the simulation results combined with the previous experimental experience could provide a feasible scheme for improving the quality of finger volume pulse signal.
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.
Artificial bone replacement has made an important contribution to safeguard human health and improve the quality of life. The application requirements of rapid prototyping technology based on reverse engineering in individualized artificial bone with individual differences are particularly urgent. This paper reviewed the current research and applications of rapid prototyping and reverse engineering in artificial bone. The research developments and the outlook of bone kinematics and dynamics simulation are also introduced.
ObjectiveTo propose a path planning method for precise robot-assisted bronchial intervention. MethodsIn the MuJoCo dynamic simulation environment, a simulation model and a simulated bronchus model which could accurately represent the motion process of the robot were built. Based on the Informed RRT* algorithm, the known spatial information was used to improve the path planning method and the motion characteristics of the robot were simulated to verify the ability of the robot algorithm to reach the target position. ResultsIn the dynamic simulation environment, the robot could move as required, and could explore the target point of the planning task in a short time, and the position accuracy was improved by more than 50% compared with the existing electromagnetic navigation and other methods. ConclusionThe established simulation model can restore the motion of the robot, and the robot has the ability to move in the bronchial environment. The proposed method can precisely control the simulated robot to enter the more peripheral airway position. It has the advantages of accuracy and faster speed than traditional manual interventional surgery, and can be used for the human-machine coordinated control task of robot-assisted bronchoscopy.
The purpose of this paper is to report the research and design of control system of magnetic coupling centrifugal blood pump in our laboratory, and to briefly describe the structure of the magnetic coupling centrifugal blood pump and principles of the body circulation model. The performance of blood pump is not only related to materials and structure, but also depends on the control algorithm. We studied the algorithm about motor current double-loop control for brushless DC motor. In order to make the algorithm adjust parameter change in different situations, we used the self-tuning fuzzy PI control algorithm and gave the details about how to design fuzzy rules. We mainly used Matlab Simulink to simulate the motor control system to test the performance of algorithm, and briefly introduced how to implement these algorithms in hardware system. Finally, by building the platform and conducting experiments, we proved that self-tuning fuzzy PI control algorithm could greatly improve both dynamic and static performance of blood pump and make the motor speed and the blood pump flow stable and adjustable.