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  • 1
    ISSN: 1573-9686
    Keywords: Coronary anatomy ; Finite element ; Network generation ; Mathematical model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A discrete anatomically accurate finite element model of the largest six generations of the coronary arterial network is developed. Using a previously developed anatomically accurate model of ventricular geometry the boundaries of the coronary mesh are defined from measured epicardial coronaries. Network topology is then generated stochastically from published anatomical data. Spatial information is added to this topological data using an avoidance algorithm accounting for global network geometry and optimal local branch angle properties. The generated vessel lengths, radii and connectivity are consistent with the published studies and a relativity even spatial distribution of vessels within the ventricular mesh is achieved. The local finite element coordinates of the coronary nodes within the ventricular mesh are calculated such that the coronary geometry can be recalculated within a deformed ventricular mesh. © 2000 Biomedical Engineering Society. PAC00: 8710+e, 8718Bb, 0270Dh
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-9686
    Keywords: Forward problem ; Electrocardiographic simulation ; Conductivity effects ; Geometric effects ; Coupled FEM/BEM ; High order interpolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract This paper investigates the effect on torso potentials of changes in the material properties of the torso volume conductor and changes in the relative geometry of the heart and torso. The investigations are performed using a number of forward simulations with a high-order coupled finite element/boundary element torso model. This torso model contains descriptions of the epicardium, lungs, skeletal muscle (with a continuously varying fiber field) and subcutaneous fat. The number of nodes, elements and solution degrees-of-freedom used in the computational torso model are considerably smaller than previous torso models of similar complexity. The successful forward simulations in this paper hence demonstrate the use of the high-order coupled approach with realistic problems. The results of the torso simulations show that the torso inhomogeneities do affect the torso potentials but do not affect the distribution or pattern of the torso potentials. The inhomogeneities considered are found to have a varying, but important, effect on the torso potentials. The effect of the subcutaneous fat is found to be more important and the effect of the skeletal muscle is found to be less important than previous reports in the literature. The results also show that the relative geometry of the heart and torso is very important in determining the torso potential magnitudes and distributions. © 2000 Biomedical Engineering Society. PAC00: 8719Hh, 8719Nn, 8719Ff, 8710+e
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-9686
    Keywords: Respiratory ; Computational model ; Lungs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract An anatomically accurate model of the conducting airways is essential for adequately simulating gas mixing, particle deposition, heat and water transfer, and fluid distribution. We have extended a two-dimensional tree-growing algorithm to three dimensions for generation of a host-shape dependent three-dimensional conducting airway model. Terminal branches in the model are both length limited and volume-supplied limited. A limit is imposed on the maximum possible branch angle between a daughter and parent branch. Comparison of the resulting model with morphometric data shows that the algorithm produces branching and length ratios, path lengths, numbers of branches, and branching angles very close to those from the experimental data. The correlation between statistics from the generated model and those from morphometric studies suggests that the conducting airway structure can be described adequately using a “supply and demand” algorithm. The resulting model is a computational mesh that can be used for simulating transport phenomena. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8710+e
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 61 (2000), S. 113-141 
    ISSN: 1573-2681
    Keywords: finite elastic deformation ; cardiac mechanics ; orthotropic constitutive relations ; fibrous-sheet tissue structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Finite elasticity theory combined with finite element analysis provides the framework for analysing ventricular mechanics during the filling phase of the cardiac cycle, when cardiac cells are not actively contracting. The orthotropic properties of the passive tissue are described here by a “pole–zero” constitutive law, whose parameters are derived in part from a model of the underlying distributions of collagen fibres. These distributions are based on our observations of the fibrous-sheet laminar architecture of myocardial tissue. We illustrate the use of high order (cubic Hermite) basis functions in solving the Galerkin finite element stress equilibrium equations based on this orthotropic constitutive law and for incorporating the observed regional distributions of fibre and sheet orientations. Pressure–volume relations and 3D principal strains predicted by the model are compared with experimental observations. A model of active tissue properties, based on isolated muscle experiments, is also introduced in order to predict transmural distributions of 3D principal strains at the end of the contraction phase of the cardiac cycle. We end by offering a critique of the current model of ventricular mechanics and propose new challenges for future modellers.
    Type of Medium: Electronic Resource
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