Modeling of Dielectric Properties of Biological Tissues by Vector Fitting (original) (raw)
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Optimised analytical models of the dielectric properties of biological tissue
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The interaction of electromagnetic fields with the human body is quantified by the dielectric properties of biological tissues. These properties are incorporated into complex numerical simulations using parametric models such as Debye and Cole-Cole, for the computational investigation of electromagnetic wave propagation within the body. These parameters can be acquired through a variety of optimisation algorithms to achieve an accurate fit to measured data sets. A number of different optimisation techniques have been proposed, but these are often limited by the requirement for initial value estimations or by the large overall error (often up to several percentage points). In this work, a novel two-stage genetic algorithm proposed by the authors is applied to optimise the multi-pole Debye parameters for 54 types of human tissues. The performance of the two-stage genetic algorithm has been examined through a comparison with five other existing algorithms. The experimental results demo...
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The dielectric properties of biological tissues have been studied widely over the past half-century. These properties are used in a vast array of applications, from determining the safety of wireless telecommunication devices to the design and optimisation of medical devices. The frequency-dependent dielectric properties are represented in closed-form parametric models, such as the Cole-Cole model, for use in numerical simulations which examine the interaction of electromagnetic (EM) fields with the human body. In general, the accuracy of EM simulations depends upon the accuracy of the tissue dielectric models. Typically, dielectric properties are measured using a linear frequency scale; however, use of the logarithmic scale has been suggested historically to be more biologically descriptive. Thus, the aim of this paper is to quantitatively compare the Cole-Cole fitting of broadband tissue dielectric measurements collected with both linear and logarithmic frequency scales. In this w...
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Physics in Medicine and Biology, 1996
A parametric model was developed to describe the variation of dielectric properties of tissues as a function of frequency. The experimental spectrum from 10 Hz to 100 GHz was modelled with four dispersion regions. The development of the model was based on recently acquired data, complemented by data surveyed from the literature. The purpose is to enable the prediction of dielectric data that are in line with those contained in the vast body of literature on the subject. The analysis was carried out on a Microsoft Excel spreadsheet. Parameters are given for 17 tissue types.
OPTIMIZATION OF MULTI-POLE DEBYE MODELS OF TISSUE DIELECTRIC PROPERTIES USING GENETIC ALGORITHM
In the past few decades many researchers have studied regarding the dielectric properties. Models of the dielectric properties of body tissues enable us to simulate the interactions of these tissues with electromagnetic fields. These properties are the permittivity and conductivity which vary many orders of the magnitude at frequencies after the microwave bands. To calculate the dielectric properties over broad frequency range, any different parametric models have been developed. Parametric formulae are available based on a multi-pole model of tissue dispersions, but although they give the dielectric properties over a wide frequency range, they do not convert easily to the time domain. An alternative is the multi pole Debye model which works well in both time and frequency domains. Optimization is needed to find the parameters that give the best fit to measured data, or to previously validated models. Genetic algorithms are an evolutionary approach to optimization and it is found that this technique is effective at finding the best values of the multi Debye parameters. Thus genetic algorithm optimizes these parameters to fit to Cole-Cole model and working well over wide frequency ranges.
An investigation of dielectric properties of biological cells using RC-model
2007
Bunthawin, S., Wanichapichart, P. and Gimsa, J. An investigation of dielectric properties of biological cells using RC-model This paper proposes a method for estimating cell dielectric properties of a spherical triple shell and ellipsoidal shell models from the Laplace and RC approaches. With a combination of various theoretical parameters such as cell dielectrophoretic velocity, angular velocity of electro-rotation (ER) and two critical frequencies of dielectrophoresis (DEP), these approaches will improve the predictability of the dielectric properties. The calibration of the model parameters to these experimental data results in estimations of the cellís electrical properties depending on the geometric structure of the assumed model.
Dielectric response of some biological tissues
Bioelectromagnetics, 2001
The dielectric properties of two freshly excised mice tissue samples (kidney, skeletal muscle) and also freshly excised Ehrlich solid tumor were measured in the frequency range from 20 Hz to 100 kHz using RLC bridges. The data were ®tted to a summation of multiple Cole±Cole dispersion and also to the constant power law which is related formally to the fractal geometries of tissues using a genetic algorithm for optimization developed by the author. The data were in good agreement with the Cole±Cole equation for the three samples. Bioelectromagnetics 22:272±279, 2001.
The dielectric properties of biological tissues: I. Literature survey
Physics in Medicine and Biology, 1996
The dielectric properties of tissues have been extracted from the literature of the past five decades and presented in a graphical format. The purpose is to assess the current state of knowledge, expose the gaps there are and provide a basis for the evaluation and analysis of corresponding data from an on-going measurement programme.
The Dielectric Properties of Biological Tissues: I
1996
The dielectric properties of tissues have been extracted from the literature of the past five decades and presented in a graphical format. The purpose is to assess the current state of knowledge, expose the gaps there are and provide a basis for the evaluation and analysis of corresponding data from an on-going measurement programme. † Present address: