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https://www.readbyqxmd.com/read/27824910/3d-finite-element-electrical-model-of-larval-zebrafish-ecg-signals
#1
James Crowcombe, Sundeep Singh Dhillon, Rhiannon Mary Hurst, Stuart Egginton, Ferenc Müller, Attila Sík, Edward Tarte
Assessment of heart function in zebrafish larvae using electrocardiography (ECG) is a potentially useful tool in developing cardiac treatments and the assessment of drug therapies. In order to better understand how a measured ECG waveform is related to the structure of the heart, its position within the larva and the position of the electrodes, a 3D model of a 3 days post fertilisation (dpf) larval zebrafish was developed to simulate cardiac electrical activity and investigate the voltage distribution throughout the body...
2016: PloS One
https://www.readbyqxmd.com/read/27737776/the-inverse-problem-in-electroencephalography-using-the-bidomain-model-of-electrical-activity
#2
Alejandro Lopez Rincon, Shingo Shimoda
BACKGROUND: Acquiring information about the distribution of electrical sources in the brain from electroencephalography (EEG) data remains a significant challenge. An accurate solution would provide an understanding of the inner mechanisms of the electrical activity in the brain and information about damaged tissue. NEW METHOD: In this paper, we present a methodology for reconstructing brain electrical activity from EEG data by using the bidomain formulation. The bidomain model considers continuous active neural tissue coupled with a nonlinear cell model...
December 1, 2016: Journal of Neuroscience Methods
https://www.readbyqxmd.com/read/27613652/analytic-modeling-of-neural-tissue-i-a-spherical-bidomain
#3
Benjamin L Schwartz, Munish Chauhan, Rosalind J Sadleir
Presented here is a model of neural tissue in a conductive medium stimulated by externally injected currents. The tissue is described as a conductively isotropic bidomain, i.e. comprised of intra and extracellular regions that occupy the same space, as well as the membrane that divides them, and the injection currents are described as a pair of source and sink points. The problem is solved in three spatial dimensions and defined in spherical coordinates [Formula: see text]. The system of coupled partial differential equations is solved by recasting the problem to be in terms of the membrane and a monodomain, interpreted as a weighted average of the intra and extracellular domains...
December 2016: Journal of Mathematical Neuroscience
https://www.readbyqxmd.com/read/27545966/joint-influence-of-transmural-heterogeneities-and-wall-deformation-on-cardiac-bioelectrical-activity-a-simulation-study
#4
P Colli Franzone, L F Pavarino, S Scacchi
The aim of this work is to investigate, by means of numerical simulations, the influence of myocardial deformation due to muscle contraction and relaxation on the cardiac repolarization process in presence of transmural intrinsic action potential duration (APD) heterogeneities. The three-dimensional electromechanical model considered consists of the following four coupled components: the quasi-static transversely isotropic finite elasticity equations for the deformation of the cardiac tissue; the active tension model for the intracellular calcium dynamics and cross-bridge binding; the anisotropic Bidomain model for the electrical current flow through the deforming cardiac tissue; the membrane model of ventricular myocytes, including stretch-activated channels...
October 2016: Mathematical Biosciences
https://www.readbyqxmd.com/read/27168382/positive-to-negative-zero-field-cooled-exchange-bias-in-la0-5sr0-5mn0-8co0-2o3-ceramics
#5
Cui Shang, Shaopu Guo, Ruilong Wang, Zhigang Sun, Haibo Xiao, Lingfang Xu, Changping Yang, Zhengcai Xia
Exchange bias effect obtained after zero-field cooling from unmagnetized state usually exhibits a shift of hysteresis loop negative to the direction of the initial magnetic field, known as negative zero-field cooled exchange bias. Here, positive zero-field cooled exchange bias is reported in La0.5Sr0.5Mn0.8Co0.2O3 ceramics. In addition, a transition from positive to negative exchange bias has been observed with increasing initial magnetization field and measurement temperature. Based on a simple spin bidomain model with variable interface, two type of interfacial spin configuration formed during the initial magnetization process are proposed to interpret the observed phenomenon...
2016: Scientific Reports
https://www.readbyqxmd.com/read/26737583/low-energy-defibrillation-with-multi-electrodes-stimulation-a-simulation-study
#6
Lian Jin, Jianfei Wang, Biao Song, Xiaomei Wu, Zuxiang Fang
The objective of this study is to explore the possible ways to reduce defibrillation energy and further reveal the mechanism of electric defibrillation. A bidomain simulation study was performed on a rabbit whole-ventricle electrophysiological model and the feasibility of the defibrillation strategy with multi-electrodes stimulation was verified. Simulation results indicate that the new approach is effective in low-energy defibrillation.
August 2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/26736753/external-current-application-in-a-bidomain-model-of-active-neural-tissue
#7
Steven F Keim, Fanrui Fu, Rosalind J Sadleir
The formal treatment of tissue as two coupled continua is referred to as a bidomain model. Bidomain models have recently been used to describe the properties of neural tissue and nerve fiber bundles [1, 2]. By adapting the Hodgkin Huxley equations in COMSOL Multiphysics, we have investigated the propagation of an action potential through neural tissue by external current stimulation.
2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/26736752/analysis-of-bipolar-external-excitation-of-spherical-tissue-by-spatially-opposed-current-source-and-sink-points
#8
Benjamin L Schwartz, Rosalind J Sadleir
The recently increasing role in medical imaging that electrophysiology plays has spurned the need for its quantitative analysis at all scales-ions, cells, tissues, organs, etc.; so, here is presented a model of nerve tissue in a spherical volume excited by a point current source at one pole and a point current sink at the opposite pole. The sphere of tissue is described as an isotropic bidomain, consisting of the intra- and extra-cellular regions and the membrane that separates them, and is immersed in an infinite isotropic conductive bath...
2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/26736750/a-3d-continuum-bidomain-model-of-retinal-electrical-stimulation-using-an-anatomically-detailed-mesh
#9
Farzaneh Shalbaf, Peng Du, Nigel H Lovell, Socrates Dokos, Ehsan Vaghefi
A continuum bidomain model of sub-retinal electrical stimulation on an anatomically detailed mesh of retina is presented. The underlying geometry is made up of 256 B-scans of optical coherence tomography (OCT) images of a healthy human retina, covering approximately 6×2 mm(2) centered on the macula. The OCT images are initially segmented and digitized into five major retinal layers comprising passive and active retinal cell types. This computational mesh is then used to model a subretinal hexapolar biphasic electrical stimulation...
2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/26685879/space-discretization-error-analysis-and-stabilization-schemes-for-conduction-velocity-in-cardiac-electrophysiology
#10
S Pezzuto, J Hake, J Sundnes
In cardiac electrophysiology, the propagation of the action potential may be described by a set of reaction-diffusion equations known as the bidomain model. The shape of the solution is determined by a balance of a strong reaction and a relatively weak diffusion, which leads to steep variations in space and time. From a numerical point of view, the sharp spatial gradients may be seen as particularly problematic, since computational grid resolution on the order of 0.1 mm or less is required, yielding considerable computational efforts on human geometries...
December 21, 2015: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/26610234/a-numerical-solution-of-the-mechanical-bidomain-model
#11
Samip Gandhi, Bradley J Roth
INTRODUCTION: The mechanical bidomain model predicts forces on integrin proteins in the membrane. It has been solved analytically for idealized examples, but a numerical algorithm is needed to address realistic problems. METHODS: The bidomain equations are approximated using finite differences. An ischemic region is modeled as a circular area having no active tension, surrounded by normal tissue. RESULTS: The membrane force is large in the ischemic border zone, but is small elsewhere...
2016: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/26583112/simulating-cardiac-electrophysiology-using-unstructured-all-hexahedra-spectral-elements
#12
Gianmauro Cuccuru, Giorgio Fotia, Fabio Maggio, James Southern
We discuss the application of the spectral element method to the monodomain and bidomain equations describing propagation of cardiac action potential. Models of cardiac electrophysiology consist of a system of partial differential equations coupled with a system of ordinary differential equations representing cell membrane dynamics. The solution of these equations requires solving multiple length scales due to the ratio of advection to diffusion that varies among the different equations. High order approximation of spectral elements provides greater flexibility in resolving multiple length scales...
2015: BioMed Research International
https://www.readbyqxmd.com/read/26560866/six-conductivity-values-to-use-in-the-bidomain-model-of-cardiac-tissue
#13
Barbara M Johnston
GOAL: The aim of this work is to produce a consistent set of six conductivity values for use in the bidomain model of cardiac tissue. METHODS: Studies in 2007 by Hooks et al. and in 2009 by Caldwell et al. have found that, in the directions longitudinal:transverse:normal (l:t:n) to the cardiac fibers, ratios of bulk conductivities and conduction velocities are each approximately in the ratio 4:2:1. These results are used here as the basis for a method that can find sets of six normalized bidomain conductivity values...
July 2016: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/26269355/the-mechanism-of-reflection-type-reentry-a-simulation-study
#14
Sunil M Kandel, Bradley J Roth
INTRODUCTION: Reflection is a special type of reentry in which an electrical wave front travels in a forward direction through tissue that is then re-excited by a wave front that propagates backward. This type of reentry has been studied computationally in 1-dimensional fibers and verified experimentally. Different hypotheses explaining reflected reentry have been proposed based on the structure and heterogeneity of the tissue properties, but the mechanism remains uncertain. METHODS AND RESULTS: We used the bidomain model to represent cardiac tissue and the Luo-Rudy model to describe the active membrane properties...
December 2015: Journal of Cardiovascular Electrophysiology
https://www.readbyqxmd.com/read/26249327/numerical-simulation-of-electrocardiograms-for-full-cardiac-cycles-in-healthy-and-pathological-conditions
#15
Elisa Schenone, Annabelle Collin, Jean-Frédéric Gerbeau
This work is dedicated to the simulation of full cycles of the electrical activity of the heart and the corresponding body surface potential. The model is based on a realistic torso and heart anatomy, including ventricles and atria. One of the specificities of our approach is to model the atria as a surface, which is the kind of data typically provided by medical imaging for thin volumes. The bidomain equations are considered in their usual formulation in the ventricles, and in a surface formulation on the atria...
May 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/26249168/pde-constrained-optimization-of-electrical-defibrillation-in-a-3d-ventricular-slice-geometry
#16
Nagaiah Chamakuri, Karl Kunisch, Gernot Plank
A computational study of an optimal control approach for cardiac defibrillation in a 3D geometry is presented. The cardiac bioelectric activity at the tissue and bath volumes is modeled by the bidomain model equations. The model includes intramural fiber rotation, axially symmetric around the fiber direction, and anisotropic conductivity coefficients, which are extracted from a histological image. The dynamics of the ionic currents are based on the regularized Mitchell-Schaeffer model. The controls enter in the form of electrodes, which are placed at the boundary of the bath volume with the goal of dampening undesired arrhythmias...
April 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/26057242/electrical-pacing-of-cardiac-tissue-including-potassium-inward-rectification
#17
Suran Galappaththige, Bradley J Roth
In this study cardiac tissue is stimulated electrically through a small unipolar electrode. Numerical simulations predict that around an electrode are adjacent regions of depolarization and hyperpolarization. Experiments have shown that during pacing of resting cardiac tissue the hyperpolarization is often inhibited. Our goal is to determine if the inward rectifying potassium current (IK1) causes the inhibition of hyperpolarization. Numerical simulations were carried out using the bidomain model with potassium dynamics specified to be inward rectifying...
2015: PloS One
https://www.readbyqxmd.com/read/26048188/determining-six-cardiac-conductivities-from-realistically-large-datasets
#18
Barbara M Johnston, Peter R Johnston
Simulation studies of cardiac electrophysiological behaviour that use the bidomain model require accurate values for the bidomain extracellular and intracellular conductivities to produce useful results. This work considers an inversion algorithm, which has previously been shown, using simulated data, to be capable of retrieving six bidomain conductivities and the fibre rotation angle from measurements of electric potential made in the heart. The aim here is to see whether it is possible to improve the accuracy of the retrieved parameters...
August 2015: Mathematical Biosciences
https://www.readbyqxmd.com/read/25836577/using-the-mechanical-bidomain-model-to-analyze-the-biomechanical-behavior-of-cardiomyocytes
#19
Bradley J Roth
The mechanical bidomain model provides a macroscopic description of cardiac tissue biomechanics and also predicts the microscopic coupling between the extracellular matrix and the intracellular cytoskeleton of cardiomyocytes. The goal of this chapter is to introduce the mechanical bidomain model, to describe the mathematical methods required to solve the model equations, and to predict where the membrane forces acting on integrin proteins coupling the intracellular and extracellular spaces are large.
2015: Methods in Molecular Biology
https://www.readbyqxmd.com/read/25773466/a-two-layers-monodomain-model-of-cardiac-electrophysiology-of-the-atria
#20
Yves Coudière, Jacques Henry, Simon Labarthe
Numerical simulations of the cardiac electrophysiology in the atria are often based on the standard bidomain or monodomain equations stated on a two-dimensional manifold. These simulations take advantage of the thinness of the atrial tissue, and their computational cost is reduced, as compared to three-dimensional simulations. However, these models do not take into account the heterogeneities located in the thickness of the tissue, like discontinuities of the fiber direction, although they can be a substrate for atrial arrhythmia (Hocini et al...
December 2015: Journal of Mathematical Biology
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