Biomechanical Parameters for Carotid Risk Assessment: A Review / 医用生物力学

Carotid is in a high risk of atherosclerosis due to its special geometric features and complex flow characteristics. Various biomechanical parameters are practical tools for carotid risk assessment. It has beenwidely accepted that oscillatory low shear environment promotes plaque formation. Based on this, more and more biomechanical indexes have been proposed, such as time-average wall shear stress, oscillatory shear index, relative residence time and so on. In this paper, multiple biomechanical parameters were introduced from the perspectives of shear stress and its temporal and spatial variation, turbulence, platelet transport and activation, stress concentration in vascular wall, etc. The development trend of biomechanical parameters related to carotid artery risk assessment was also analyzed, so as to provide the theoretical basis for more comprehensive and rapid carotid risk assessment

Research Progress in Computational Simulation of Thrombosis / 医用生物力学

Thrombosis is the process of platelet adhesion and aggregation or blood coagulation after the body is subjected to certain physical and chemical stimuli. At present, the use of basic experimental research and computational simulation to understand thrombosis has become a research hotspot. The complex process of thrombosis makes computational modeling very difficult, but the development of calculation models has still made great progress. At present, a variety of calculation models for thrombosis have been developed, including coagulation models based on ordinary differential equations, mathematical models based on finite element analysis, Lattice-Boltzmann method models, smooth particle dynamics method models, etc. Each model has its advantages and disadvantages.In this review, the physiological mechanism of thrombosis was explained, the models for simulating thrombosis were also systematically sorted out and evaluated, and the limitations of computational simulation and future application prospects were summarized as well.

Index of microcirculatory resistance: state-of-the-art and potential applications in computational simulation of coronary artery disease / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

The dysfunction of coronary microcirculation is an important cause of coronary artery disease (CAD). The index of microcirculatory resistance (IMR) is a quantitative evaluation of coronary microcirculatory function, which provides a significant reference for the prediction, diagnosis, treatment, and prognosis of CAD. IMR also plays a key role in investigating the interaction between epicardial and microcirculatory dysfunctions, and is closely associated with coronary hemodynamic parameters such as flow rate, distal coronary pressure, and aortic pressure, which have been widely applied in computational studies of CAD. However, there is currently a lack of consensus across studies on the normal and pathological ranges of IMR. The relationships between IMR and coronary hemodynamic parameters have not been accurately quantified, which limits the application of IMR in computational CAD studies. In this paper, we discuss the research gaps between IMR and its potential applications in the computational simulation of CAD. Computational simulation based on the combination of IMR and other hemodynamic parameters is a promising technology to improve the diagnosis and guide clinical trials of CAD.

Effect of temperature in bursting of thalamic reticular cells / Efecto de la temperatura en las descargas en ráfaga de la célula del núcleo reticular del tálamo

Abstract Objective: To show the relation between the four parameters associated to bursting discharges of the thalamic reticular cells (TRNn): the maximum firing frequency (fmax) and the temperature at which it occurs (Tfmax), the range of temperatures defined as the full width at half maximum (∆Th) and the maximum specific low threshold calcium conductance (GT). Materials and Methods: In order to simulate the TRNn bursting activity, a computational simulation model was implemented using the NEURON software, which incorporates morphological and electrophysiological data, and stimuli properties closely related to reality. Results: It was found that there are nonlinear relations between the parameters. The fmax frequency follows a quadratic growth with temperature and tends asymptotically towards a limit value with the maximum calcium conductance. In the same manner, ∆Th increases until reaching a limit value as function of fmax and GT. However, the increment per frequency unit is bigger than the increment per conductance unit. Conclusions: Four equations were obtained that model the relations between the parameters associated to bursting discharges of the TRNn in rats and other neurons with similar characteristics in different animal species.

Resumen Objetivo: Mostrar la relación entre los cuatro parámetros asociados a las descargas en ráfaga de las neuronas del núcleo reticular del tálamo (TRNn): la frecuencia máxima de descarga (fmax) y la temperatura a la cual se produce (Tfmax), el rango de temperaturas definido como ancho a media altura (∆Th) y la conductancia máxima de calcio de bajo umbral (GT). Materiales y métodos: Para simular las descargas en ráfaga de las TRNn se implementó un modelo de simulación computacional usando el software NEURON, que incorpora datos morfológicos, electrofisiologicos y las propiedades de los estímulos en estrecha relación con la realidad. Resultados: Se encontraron relaciones no lineales entre los parámetros. La frecuencia fmax crece de forma cuadrática con la temperatura y tiende asintóticamente a un valor límite con la conductancia. Así mismo, ∆Th también se incrementan hasta alcanzar un valor límite en función de fmax y GT. No obstante, es mayor el incremento por cada unidad de frecuencia que por cada unidad de conductancia. Conclusiones: Se obtuvieron cuatro ecuaciones que modelan las relaciones entre los pará- metros asociados a las descargas en ráfaga de las neuronas TRN en ratas y otras neuronas con características similares en diferentes especies animales.

Computational Simulation of Multiple Cannulated Screw Fixation for Femoral Neck Fractures and the Anatomic Features for Clinical Applications

PURPOSE: To identify the anatomic features for clinical applications through a computational simulation of the fixation of three cannulated screws for a femoral neck fracture. MATERIALS AND METHODS: Thirty cadaveric femurs underwent computed tomography and the images were transferred to the Mimics® program, resulting in three-dimensional proximal femur models. A three-dimensional scan of the 7.0 mm cannulated screw was performed to enable computerized virtual fixation of multiple cannulated screws for femoral neck fractures. After positioning the screws definitively for cortical support, the intraosseous position of the cannulated screws was evaluated in the anteroposterior image and axial image direction. RESULTS: Three cannulated screws located at the each ideal site showed an array of tilted triangles with anterior screw attachment and the shortest spacing between posterior and central screws. The central screw located at the lower side was placed in the mid-height of the lesser trochanter and slightly posterior, and directed toward the junction of femoral head and neck to achieve medial cortical support. All the posterior screws were limited in height by the trochanteric fossa and were located below the vastus ridge, but the anterior screws were located higher than the vastus ridge in 10 cases. To obtain the maximum spacing of the anterior and posterior screws on the axial plane, they should be positioned parallel to the cervical region nearest the cortical bone at a height not exceeding the vastus ridge. CONCLUSION: The position of cannulated screws for cortical support were irregular triangular arrangements with the anterosuperior apex. The position of the ideal central screw in the anteroposterior view was at the mid-height of the lesser trochanter toward the junction of the femoral head and neck, and the anterior and posterior screws were parallel to the neck with a maximal spread just inferior to the vastus ridge.

Numerical simulation of heat transfer in a canine knee joint in thermal neutrality: analysis of the influence of different values of blood perfusion and considerations of the blood perfusion rate / Simulação numérica da transferência de calor na articulação do joelho canino em neutralidade térmica: análises das influências dos diferentes valores de perfusão sanguínea e das considerações da taxa de perfusão sanguínea

This study aimed to simulate heat transfer in thermal equilibrium in the canine knee joint. We analyzed the impact of different values of blood perfusion available in the literature and considered blood perfusion rates. The geometric models of canine knee joints were created from a photographic record of a cross section of an anatomical part. Two geometric models were developed: one without the epidermis and one with the epidermis. A heat diffusion equation was used to model the heat transfer phenomenon. Numerical simulations of the canine knee in a thermal neutrality condition were performed using the ANSYS-CFX® program. The simulation results were compared with experimental in vivo data. The smaller percentage differences between the experimental and simulated in vivo results were found in simulations that used the blood flow rate as a function of temperature. The computer simulation proved to be a good alternative to evaluate the temperature of biological tissues.

O presente trabalho visa simular a transferência de calor, em equilíbrio térmico, na articulação do joelho canino e analisar o impacto dos diferentes valores de perfusão sanguínea disponíveis na literatura e das considerações da taxa de perfusão sanguínea. Os modelos geométricos da articulação do joelho canino foram criados com base em um registro fotográfico de um corte transversal de uma peça anatômica. Foram desenvolvidos dois modelos geométricos: 1- sem epiderme e 2 ­ com epiderme. A equação de difusão de calor foi utilizada para modelar o fenômeno de transferência de calor. As simulações numéricas do joelho canino na condição de neutralidade térmica foram realizadas utilizando o programa ANSYS-CFX®. Os resultados da simulação foram comparados com os dados experimentais in vivo. As menores diferenças percentuais, entre o experimento in vivo e os resultados simulados, foram encontradas nas simulações que utilizaram a taxa de perfusão sanguínea em função da temperatura. A simulação computacional mostrou-se uma boa alternativa para avaliar a temperatura dos tecidos biológicos.

Effect of Ceramic Thickness and Composite Bases on Stress Distribution of Inlays - A Finite Element Analysis

The purpose of this study was to determine the effect of cavity depth, ceramic thickness, and resin bases with different elastic modulus on von Mises stress patterns of ceramic inlays. Tridimensional geometric models were developed with SolidWorks image software. The differences between the models were: depth of pulpal wall, ceramic thickness, and presence of composite bases with different thickness and elastic modulus. The geometric models were constrained at the proximal surfaces and base of maxillary bone. A load of 100 N was applied. The stress distribution pattern was analyzed with von Mises stress diagrams. The maximum von Mises stress values ranged from 176 MPa to 263 MPa and varied among the 3D-models. The highest von Mises stress value was found on models with 1-mm-thick composite resin base and 1-mm-thick ceramic inlay. Intermediate values (249-250 MPa) occurred on models with 2-mm-thick composite resin base and 1-mm-thick ceramic inlay and 1-mm-thick composite resin base and 2-mm-thick ceramic inlay. The lowest values were observed on models restored exclusively with ceramic inlay (176 MPa to 182 MPa). It was found that thicker inlays distribute stress more favorably and bases with low elastic modulus increase stress concentrations on the internal surface of the ceramic inlay. The increase of ceramic thickness tends to present more favorable stress distribution, especially when bonded directly onto the cavity without the use of supporting materials. When the use of a composite base is required, composite resin with high elastic modulus and reduced thickness should be preferred.

O objetivo do estudo foi avaliar o efeito da profundidade da cavidade, da espessura da cerâmica e da presença de bases de resina, com os diferentes módulos de elasticidade na distribuição de tensões de von Mises em inlays cerâmicos. Modelos geométricos tridimensionais foram desenvolvidos com o software SolidWorks. As diferenças entre os modelos foram: a profundidade da parede pulpar, a espessura da cerâmica e a presença de bases de resina composta com diferentes espessuras e módulos de elasticidade. Os modelos geométricos foram engastados nas superfícies proximais e base do osso maxilar e uma carga de 100 Newton foi aplicada. O padrão de distribuição de tensões foi analisado com diagramas de tensão de von Mises. O valor de tensão máxima de von Mises foi variável entre os modelos e situou-se na faixa entre 176 e 263 MPa. O maior valor foi encontrado nos modelos restaurados com bases de resina composta de 1 mm e inlay cerâmico de 1 mm de espessura. Valores intermediários (249-250 MPa) ocorreram nos modelos com bases de resina composta de 2 mm e inlays de 1 mm de espessura e nos modelos com bases de resina composta de 1 mm e inlays de 2 mm. Os menores valores foram observados nos modelos restaurados exclusivamente com inlay cerâmico (176-182 MPa). Verificou-se que inlays com maior espessura distribuem o estresse de forma mais favorável e bases com baixo módulo de elasticidade aumentam a concentração de tensões na superfície interna do inlay de cerâmica. O aumento da espessura do material cerâmico tende a apresentar uma distribuição de tensões mais favorável, principalmente quando cimentadas diretamente sobre o preparo cavitário, sem a existência de materiais intermediários. Em situações em que o emprego de materiais de base é necessária, deve-se preferir resinas compostas com alto módulo de elasticidade e espessura reduzida.

Application of computational simulation and spectral analysis in preparation of Tanshinone IIA imprinted polymer / 中草药

To prepare Tanshinone IIA (TSIIA) molecularly imprinted polymers (MIPs) with affinity and high selectivity to TSIIA and study its mechanism. Taking TSIIA as the template molecular, synthesizing the MIPs at the surface of silica nanoparticles by grafting copolymerization in the toluene solution. A molecular modeling approach was used to elucidate template-monomer interaction. The interaction between template molecule and functional monomer was studied by UV spectrometry. The theoretical molar ratio of template-monomer was 1∶3 and methyl acrylic acid (MAA) was a better functional monomer than acrylamide (AAM) for MIPs synthesis. The MIPs can be used for the extraction and separation of TSIIA.

Data Exporter: A complementary tool to export data simulation from neuron / Data Exporter: Una herramienta complementaria para exportar datos obtenidos de simulaciones con neuron

Objectives: To develop a computational tool for NEURON simulation environment, user friendly, to store the results generated during simulation and to make subsequent analysis with other tools such as Matlab and IgorPRo Materials and Methods: Data Exporter was implemented in the programming language hoc. This algorithm is divided in 13 sections or blocks. The first section is necessary to edit in a new simulation. These new configuration determine the geometry, biophysic properties the neurons to simulate and path to save data. Results: To check the efficiency of the algorithm, we simulated the propagation of action potential in TRN(thalamic reticular nucleus) neuron in different large of simulation. We determine that the time of simulation is linear respect to time of simulation. Conclusions: Data Exporter makes easier to start to neural simulation in NEURON reducing the steps of programming to geometry and biophysical properties of the neuron and to allow save data to next steps of analysis.

Objetivos: Desarrollar una herramienta computacional en ambiente lenguaje de programación hoc de NEURON y de fácil uso, que permita el rápido almacenamiento de los resultados obtenidos para su posterior análisis en otros software tales como Matlab or IgorPro. Materiales y métodos: Para el desarrollo de Data Exporter se escribió un algoritmo en lenguaje de programación hoc de NEURON. El algoritmo, escrito en un único archivo de texto, esta dividido en 13 bloques, de los cuales solo el primero debe ser modificado para adaptarlo a una geometría y biofísica neuronal particular y para determinar la ruta de almacenamiento de los datos. Resultados: Se desarrollo un software que simula la propagación de potenciales de acción a través de geometrías neuronales complejas. El uso de esta herramienta permite el almacenamiento de los resultados obtenidos, como potenciales y corrientes de membrana en diferentes puntos de toda la neurona, sin incremento significativo en el tiempo para el desarrollo de los procesos. Conclusiones: Data Exporter es un software que le da mayor flexibilidad a NEURON facilitando el acceso a nuevos neurocientíficos, los cuales pueden usarlo con solo conocer los códigos necesarios para el desarrollo de los archivos relacionados con las propiedades geométricas y biofísicas neuronales.

Análise computacional do dano térmico no olho humano portador de um melanoma de coroide quando submetido à termoterapia transpupilar a laser / Computational analysis of thermal damage in the human eye carrying a choroidal melanoma when exposed to laser transpupillary thermotherapy treatment

Este trabalho apresenta um modelo bidimensional do olho humano para investigar a evolução da temperatura em estado transitório e o dano térmico associado nas camadas do olho e, principalmente, no melanoma de coroide. A modelagem e simulação computacional foram executadas para um paciente portador de um melanoma de coroide, submetido a um tratamento por irradiação com laser. Para determinar o campo de temperaturas, foi desenvolvido um modelo que utiliza a equação da biotransferência de calor de Pennes (BHTE - Bioheat Transfer Equation) que possui um termo de fonte/sumidouro que responde pelo calor transferido através da perfusão sanguínea. O modelo de Birngruber foi utilizado para determinar a função dano térmico durante a termoterapia transpupilar a laser (TTT). A análise foi efetuada a partir de uma imagem de ultrassom do paciente. Este tipo de exame forneceu as dimensões do olho e do tumor. O software comercial de CFD (Computational Fluid Dynamics) FLUENT, que emprega o Método dos Volumes Finitos (MVF), foi utilizado nas análises do modelo. Foram calculadas as temperaturas em estado estacionário para o olho não irradiado e estes resultados foram utilizados como condição inicial para a simulação de estado transitório para o olho irradiado, durante 60 segundos, com um laser de diodo (810 nm e potências de saída de 178, 222, 400 e 500 mW) cujos feixes apresentavam diâmetros de 2,0 e 3,0 mm e intensidades de 56.588 W/m² e 70.736 W/m² sobre a córnea. Para validar o modelo, os resultados das temperaturas, em estado estacionário para o olho não exposto à radiação do laser, foram comparados com outros mostrando uma boa concordância entre eles. Os resultados das temperaturas e do dano térmico, estado transitório, para o olho irradiado com o laser estão, qualitativamente, em acordo com a literatura disponível.

This paper presents a two-dimensional model of the human eye to investigate the evolution of temperature in transient state and the associated thermal damage in the layers of the eye and, especially in the choroidal melanoma. The computer modeling and simulation were performed for a patient with a choroidal melanoma, undergoing treatment by laser irradiation. To determine the temperature field, we developed a model that uses the Pennes Bioheat Transfer Equation (BHTE) that has a term of source/sink that responds to the heat transferred through the blood perfusion. The Birngruber model was used to determine the function of thermal damage during the laser transpupillary thermotherapy (TTT). The analysis was carried out from an ultrasound image of the patient. This type of examination provided the dimensions of the eye and the tumor. The CFD (Computational Fluid Dynamics) commercial software FLUENT&®, which uses the Finite Volume Method (FVM) was used in the analysis of the model. The temperatures, steady-state, were calculated for the normal eye, i.e, without laser irradiation and these results were used as initial condition for the simulation of transient state to the eye irradiated for 60 seconds with a diode laser (810 nm and output power of 178, 222, 400 and 500 mW) whose beam had a diameter of 2.0 to 3.0 mm and irradiance of 56,588 and 70,736 W/m² on the cornea. To validate the model, the results of temperatures, in steady state to the eye not exposed to laser radiation, were compared with others showing a good agreement between them. The results of thermal damage and transient state, for the eye irradiated by the laser, show that the values of damage depth are in agreement with the literature.

Micropatterning of endothelial cells on poly-dimethylsiloxane flow channel bottom / 第三军医大学学报

Objective To simulate the blood flow features of the susceptible sites of atherosclerosis in vitro.The cell micro-patterning is to be obtained on the bottom of channel for the information about single cell or cell groups.Methods Poly-dimethylsiloxane(PDMS) flow channel and PDMS stamp were fabricated by soft lithography.Fibronectin pattern was formed on chamber bottom by micro-contact printing method and cells selectively attached on fibronectin pattern.Results The PDMS-patterned chamber that possessed favorable optical property and the PDMS stamps with different sizes were obtained.Cells attached on fibronectin pattern presented square array.Conclusion The fabricated methods are quick and simple.The chamber could be used for the advanced real-time investigation of cell mechanical behavior in vitro.

On the modelling bone tissue fracture and healing of the bone tissue / Sobre el modelado de los procesos de fra ctura y reparacion del tejido óseo

This paper reviews the available literature on computational modelling in two areas of bone biomechanics: fracture and healing. Bone fracture analysis attempts to predict the failure of musculoskeletal structures by several possible mechanisms under different loading conditions. However, as opposed to structurally inert materials, bone is a living tissue that can repair its elf. An exciting new field of research is being developed to better comprehend these mechanisms and the mechanical behaviour of bone tissue. One of the main goals of this work is to demonstrate, after a review of computational models, the main similarities and differences between normal engineering materials and bone tissue from a structural point of view. We also underline the importance of computational simulations in biomechanics due to the difficulty of obtaining experimental or clinical results.

La fractura de todo tipo en los órganos óseos es una de las causas indirectas más importantes de mortalidad en personas de avanzada edad y uno de los factores de mayor incidencia social y económica dentro del ámbito sanitario en las sociedades desarrolladas. Es por tanto importante disponer de una mejor comprensión de los mecanismos de fractura ósea y de los modelos necesarios que tratan de predecir su fallo como consecuencia de diferentes condiciones de carga. Sin embargo, a diferencia de lo que ocurre en materiales inertes, el hueso, como tejido vivo, tiene la capacidad de autorepararse. De hecho el mejor conocimiento de estos comportamientos, junto a la posibilidad de simulaciones suficientemente precisas, permitiría un mejor diseño de prótesis e implantes, siendo éste un campo de investigación de gran actualidad. Los objetivos principales de este trabajo son comprender las diferencias y similitudes entre el comportamiento a fractura entre el tejido óseo y los materiales ingenieriles habituales desde un punto de vista estructural, así como realizar una revisión de la bibliografía disponible sobre el modelado computacional en estas dos áreas de la Biomecánica ósea: fractura y conformación del callo óseo, con objeto de enfatizar la importancia de la simulación en esta disciplina,, debido a la enorme dificultad, e incluso imposibilidad en muchos casos, de obtener resultados experimentales precisos y personalizados.