The admittance method is a numerical electromagnetic method in which the problem space is discretely partitioned and its electrical properties represented in terms of an admittance network created from the dielectric properties of the intervening materials. In the presence of electromagnetic stimulation, the electrical response of the problem space is approximated as the response of the admittance network to a stimulus representative of the original source. In this work, a three-dimensional multiresolution admittance method adequate for solving large scale bioelectromagnetic models is introduced. The formulation is applied to modeling and simulation of retinal implantable stimulation arrays and electrical injury by electroporation.
A distinctive advantage of using the admittance method for bioelectromagnetic simulations is that the method implies a representation of the system in terms of an electric network. Examples of applications where this method can be of use are the modeling of metal-electrolyte interfaces for implanted electrodes, and the simulation of electrical behavior of neural cells using three-dimensional variations of the core-conductor model. Because arbitrary circuital elements can be added to an admittance network to model physiological behavior, the admittance method (and its dual, the impedance method) can, in principle, be used to bridge the gap between tissue level and cellular level modeling. Even though numerical treatments of bioelectromagnetic phenomena using the admittance and impedance methods have been available for several decades, detailed modeling of large biological structures has presented unique challenges, as the shapes of anatomical structures tend to be complex, and frequently the sizes of features that must be resolved are small compared to the overall size of the model. The multiresolution algorithm presented in this dissertation addresses these issues by greatly reducing the resulting voxel count while keeping an error comparable to the uniform resolution cases. This is achieved by selectively maintaining high resolutions at material boundaries while progressively increasing voxel size inside large homogeneous volumes. At difference of previous treatments of the admittance method, which solved static or single-frequency (frequency domain) models, the proposed formulation can take advantage of time-stepping to simulate the effect of excitation using signals of arbitrary waveforms.
|School:||North Carolina State University|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 72/10, Dissertation Abstracts International|
|Subjects:||Biomedical engineering, Electrical engineering, Environmental science|
|Keywords:||Admittance method, Electrical injury models, Multiresolution, Numerical electromagnetics, Retinal prosthesis|
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