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Mild hypothermia, as a common means of intraoperative nerve protection, has been used in clinical practice. Compared with the traditional methods such as freezing helmet and nasopharyngeal cooling, hypothermic blood perfusion is considered to be a promising treatment for mild hypothermia, but it lacks experimental and theoretical verification of its cooling effect. In this study, the commercial finite element simulation software COMSOL combined the Pennes equation with the cerebrovascular network model to construct a new simplified human brain model, which was further used to simulate the cooling process of cerebral hypothermic blood perfusion. When the hypothermic blood perfusion was 33 ℃, the human brain could enter the mild hypothermic state within 4 minutes. By comparing with helmet cooling, the feasibility and efficiency of the blood perfusion scheme were verified. By comparing with the calculation results based on Pennes equation, the rationality of the model constructed in this study were verified. This model can non-intrusively predict the changes of brain temperature during surgery, and provide a reference for the setting of treatment parameters such as blood temperature, so as to provide personalized realization of safer and more effective mild hypothermia neuro protection.
Subject(s)
Humans , Hypothermia, Induced/methods , Hypothermia , Hemoperfusion , Brain/physiology , Body TemperatureABSTRACT
Objective To propose an airbag-type helmet cushioning lining structure and analyze its protective effect on head injury of two-wheeled bicycle riders. Methods The airbag lining was applied to two typical two-wheeled bicycle helmets for bicycles (half helmets) and motorcycles (full helmets). Then kinematic and biomechanical responses of the human head model were predicted from impact simulations under test conditions of the standard GB 24429-2009 and the regulations ECE R22.05, and conventional expanded polystyrene (EPS) helmets were compared from the perspective of skull fracture and brain injury risk, so as to make comprehensive evaluation on protective performance of the airbag helmet. Results When the airbag pressure was 0.06 MPa, the relevant amount of human skull fracture under protection of airbag helmet (half/full helmet) was smaller than 120 g and 150 g, respectively; the risk of skull fracture was basically lower than 40%; the maximum principal strains of the brain were both smaller than 0.3, which indicated that the risk of mild brain injury was lower than 25%. Generally, the risk of human skull fracture and head injury under protection of airbag helmets was lower than that under protection of EPS helmets. Conclusions The airbag helmet designed in this study has a good protective effect, which can give attention to the protection of both skull fracture and head injury, providing a basic example for the design of novel helmet. Injury risk analysis can also provide the preliminary reference for emergency diagnosis on head injury of cyclists.
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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.
Subject(s)
Computer Simulation , Fingers , Finite Element Analysis , Skin , SoftwareABSTRACT
Spinal cord stimulation (SCS) for pain is usually implanted as an open loop system using unchanged parameters. To avoid the under and over stimulation caused by lead migration, evoked compound action potentials (ECAP) is used as feedback signal to change the stimulating parameters. This study established a simulation model of ECAP recording to investigate the relationship between ECAP component and dorsal column (DC) fiber recruitment. Finite element model of SCS and multi-compartment model of sensory fiber were coupled to calculate the single fiber action potential (SFAP) caused by single fiber in different spinal cord regions. The synthetized ECAP, superimposition of SFAP, could be considered as an index of DC fiber excitation degree, because the position of crests and amplitude of ECAP corresponds to different fiber diameters. When 10% or less DC fibers were excited, the crests corresponded to fibers with large diameters. When 20% or more DC fibers were excited, ECAP showed a slow conduction crest, which corresponded to fibers with small diameters. The amplitude of this slow conduction crest increased as the stimulating intensity increased while the amplitude of the fast conduction crest almost remained unchanged. Therefore, the simulated ECAP signal in this paper could be used to evaluate the degree of excitation of DC fibers. This SCS-ECAP model may provide theoretical basis for future clinical application of close loop SCS base on ECAP.
Subject(s)
Action Potentials , Computer Simulation , Electric Stimulation , Evoked Potentials , Spinal Cord , Spinal Cord StimulationABSTRACT
Objective To design a notched flexible articulation applied to electric stapler and study its turning performance. Methods The notched flexible articulation was designed and modeled. The kinematics and statics models of the articulation were established for simulation calculations. The stress, deflection angle, top displacement and driving force of the articulation with 3 different turning structures were studied under equal and variable stiffness of symmetrical notches by using finite element simulation. An experimental platform for performance test of the turning structure was built to verify the simulation results and the model. Results The theoretical model of the turning structure in bending process was basically consistent with the experimental results. With the optimization of symmetrical notch stiffness, the maximum stress of the articulation with variable stiffness was reduced by 20.64% and 39.20%, respectively. The articulation with variable stiffness required the smallest tensile force during bending, which was 33.41% lower than that of the articulation with equal stiffness, and the tip displacement (30.8 mm) along the bending plane was the smallest. The maximum deflection angle for the articulation with 3 different turning structures all could reach 90°. Conclusions The kinematics and statics models of the articulation can be used for the calculation of its tensile force and position changes. The turning performance of the articulation with variable stiffness using symmetrical notch is better than that with equal stiffness. The notched flexible articulation meets the design requirements and the turning needs of electric stapler.
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Numerical simulation of stent deployment is very important to the surgical planning and risk assess of the interventional treatment for the cardio-cerebrovascular diseases. Our group developed a framework to deploy the braided stent and the stent graft virtually by finite element simulation. By using the framework, the whole process of the deployment of the flow diverter to treat a cerebral aneurysm was simulated, and the deformation of the parent artery and the distributions of the stress in the parent artery wall were investigated. The results provided some information to improve the intervention of cerebral aneurysm and optimize the design of the flow diverter. Furthermore, the whole process of the deployment of the stent graft to treat an aortic dissection was simulated, and the distributions of the stress in the aortic wall were investigated when the different oversize ratio of the stent graft was selected. The simulation results proved that the maximum stress located at the position where the bare metal ring touched the artery wall. The results also can be applied to improve the intervention of the aortic dissection and the design of the stent graft.
Subject(s)
Humans , Arteries , Blood Vessel Prosthesis Implantation , Cardiovascular Diseases , Computer Simulation , Finite Element Analysis , Prosthesis Design , StentsABSTRACT
Objective To make drilling mechanical and thermal analysis of bones with different drill bits and drilling parameters, so as to reduce the drilling force and drilling temperature in drilling process and decrease the damage to surrounding bone tissues. Methods The bone drilling model was established by finite element simulation software AdvantEdge. By comparison with the pig femur drilling experiment, the simulated and experimental results of standard twist driII and three standard multi-facet drills at different speeds and feed rates were analyzed. Results The simulation and experiment comparison showed that the influences of driII bit structure, drilling speed, feed rate on drilling force and drilling temperature were consistent, and the established simulation model was credible. Conclusions Under the same drilling conditions, the multi-facet driII for drilling rubber had lower drilling force and drilling temperature than the standard twist drill. The research findings provide theoretical basis for the application of multi-facet driII in fracture surgery.
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BACKGROUND: Different bone materials have different properties. Therefore, to simplify the model and improve the analysis efficiency in biomechanical analysis, many scholars have adopted different assignment methods to the bone model in the biomechanical simulation research. The distribution of material properties will have a great influence on the results of biomechanical analysis. OBJECTIVE: Three kinds of finite element models of the femur were established by different material attribute assignment methods, and the finite element simulation analysis was carried out to explore the influence of different material assignment methods on the biomechanical simulation analysis of femur finite element. METHODS: Volunteer femur CT scanning data were collected and imported into Mimics medical image processing software in DICOM format to reconstruct the femur model. Three different material attributes were assigned to the models, including uniform material assignment, skin cancellous bone assignment and gray scale assignment. The models were imported into finite element analysis Abaqus 6.14 software to set the same load and boundary conditions for stress and displacement analysis. RESULTS AND CONCLUSION: (1) The stress values of the three kinds of models differed slightly and were all in a reasonable range. (2) Whereas, the maximum stress of homogeneous assigned model and the model assigned according to cortical-cancellous bone assembly model mainly distributed in the diaphysis region, while the maximum stress distributed in the femoral neck region for the gray value assigned model. (3) The displacement value of cortical-cancellous bone assigned model was essentially in agreement with the gray value assigned model. The homogeneous assigned femoral model possessed the minimum displacement value and the value was about 40% different from the other two models. (4) The grayscale method can better reflect the biomechanical characteristics of human femur, so as to more accurately simulate the real biomechanical characteristics of real femur, which also provides an important theoretical basis for the finite element simulation modeling of orthopedic biomechanics.
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Objective Finite element numerical simulation technique was applied to simulate the dynamic projectile injury process of human chin in different injury conditions and the mechanism of injury was discussed by using biomechanical analysis . Methods The 3D finite element model of human mandible projective injury was established to simulate the dynamic projectile inju‐ry process of human chin in different injury conditions (high ,medium and low speeds) ,and the simulation results were used to com‐parative analysis of biomechanics .Results The dynamic damage process of human chin projectile injury was simulated successfully in different injury conditions ,and the more serious injury of mandible was caused by faster speed .Conclusion The finite element method can simulate the projectile injury of mandible effectively ,and can provide a new thought and method for basic research and clinical treatment of oral and maxillofacial war injury .
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Objective In order to fully reconstruct the accident by utilizing pedestrian injuries information gained from the car-pedestrian collision, a new method based on finite element simulation and genetic neural network to deduce the car-pedestrian collision parameters in reverse is proposed. Methods Crash simulations from different contact angles (back, left, front, right) at different impact speeds (25, 40, 55 km/h) were conducted by using Hyperworks and LS-DYNA, so as to obtain the head injury criterion (HIC) value and the maximum velocity of the thoracic wall. According to the criteria of injury biomechanics, the severities of the pedestrian head and thorax and corresponding injury locations were analyzed and set as predictors, and the predictive values of collision parameters were then acquired by using genetic neural network. Finally, this method was verified by two car-pedestrian accidents with the video and exact collision parameters. Results For both cases of the car-pedestrian accidents, the car speeds at the collision of pedestrian were 54 and 49 km/h, respectively, and the car-pedestrian contact angles were both 180°. While according to the pedestrian injuries information, the predictive values of the car speeds at the collision of pedestrian were 51 and 43 km/h, and the predictive values of the car-pedestrian contact angles were 184° and 169°, respectively. The reconstruction accuracies of two cases were 0.94 and 0.88. Conclusions The proposed method in the study can be used to predict car-pedestrian collision parameters efficiently and accurately by utilizing the pedestrian injuries information, which provides a new method for cause analysis and responsibility recognition, as well as theoretical references for the treatment and protection of head and thoracic injuries occurred in the car-pedestrian collision.
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PURPOSE: The aim of this study was to investigate the effect of implant thread profile on the marginal bone stresses which develop during implant insertion. MATERIALS AND METHODS: Four experimental implants were created by placing four different thread systems on the body (4.1 mm x 10 mm) of the ITI standard implant. The thread types studied in this study included the buttress, v-shape, reverse buttress, and square shape threads. In order to examine the insertion stress generation, 3D dynamic finite element analysis was performed which simulated the insertion process of implants into a 1.2 mm thick cortical bone plate (containing 3.5 mm pilot hole) using a PC-based DEFORM 3D (ver 6.1, SFTC, Columbus, OH, USA) program. RESULTS: Insertion stresses higher than human cortical bone developed around the implants. The level of insertion stresses was much different depending on the thread. Stress level was lowest near the v-shape thread, and highest near the square shaped thread. Difference in the interfacial bone stress level was more noticeable near the valley than the tip of the threads. CONCLUSION: Among the four threads, the v-shape thread was turned out to minimize the insertion stress level and thereby create better conditions for implant osseointegration.
Subject(s)
Humans , Bone Plates , Finite Element Analysis , Implants, Experimental , OsseointegrationABSTRACT
Adielectrophoresis-basedmicrofluidicchipappliedtocellspatterningisdesignedandfabricated, and it demonstrates non-contact and batch manipulation of cells. The microfluidic chip employs a PDMS microchannel and two ITO electrodes, which are designed as astep shape. The distribution of electric field caused by the microelectrodes is simulated by finite element simulation software, COMSOL. The position of the maximum intensity of electric field is also determined. The ITO microelectrodes and the PDMS microchannel are fabricated using MEMS fabrication process. After oxygen plasma surface treatment, the PDMS microchannel and glass substrate with the ITO microelectrodes are aligned and bonded to form experimental microfluidic chip. Through DEP experiment with the varying frequencies, DEP response of yeast cells is examined, and the electric field frequency of the both positive and negative DEP responses are confirmed. The results showed that yeast cells in solution conductivity of 60 μS/cm had negative DEP movement at the frequency of 1 kHz to 10 kHz, positive DEP movement at the 500 kHz to 10 MHz, and no DEP movement at the 50 kHz. Under the condition of the sinusoidal potential of 8Vp-p and the electric field frequency of 5 MHz, the yeast cells were aligned into chains along the step edge of microelectrodes.
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Se presenta la implementación numérica del modelo bioquímico descrito mediante el sistema de reacción-difusión de la parte 1. De los resultados obtenidos se puede concluir que la retroalimentación química de los 2 factores moleculares a través de un sistema de reacción-difusión (RD) con parámetros en el espacio de Turing, puede explicar la aparición de los patrones espacio-temporales encontrados en la arquitectura de la espongiosa primaria. Para la solución numérica fue usado el método de los elementos finitos junto con el método de Newton-Raphson para aproximar las ecuaciones diferenciales parciales lineales. Los patrones de osificación obtenidos pueden representar la formación de la espongiosa primaria durante la osificación endocondral...
A presentation is made of the numerical implementation of the biochemical model described by means of the reaction-diffusion system in Part 1. Based on the results obtained it may be concluded that the chemical feedback of the two molecular factors by means of a reaction-diffusion (RD) system with Turing space parameters may explain the appearance of the spatio-temporal patterns found in the architecture of the primary spongiosa. For the numerical solution, use was made of the finite element method in combination with the Newton-Raphson method to approximate the linear partial differential equations. The ossification patterns obtained may represent the formation of the primary spongiosa during endochondral ossification...