Electric properties of tissues
14 Apr 2006-
TL;DR: The electrical properties of biological tissues and cell pensions have been of interest for over a century for manyreasons, such as the ability to determine the pathways of current flow through the body and, thus, are very important in theanalysis of a wide range of biomedical applications such as functional electrical stimulation and the diagnosis and treatment of various physiological conditions with weakelectric currents, radiofrequency hyperthermia, electro-cardiography, and body composition as mentioned in this paper.
Abstract: 1. INTRODUCTIONThe electrical properties of biological tissues and cell sus-pensions have been of interest for over a century for manyreasons. They determine the pathways of current flowthrough the body and, thus, are very important in theanalysis of a wide range of biomedical applications such asfunctional electrical stimulation and the diagnosis andtreatment of various physiological conditions with weakelectric currents, radio-frequency hyperthermia, electro-cardiography, and body composition. On a more funda-mental level, knowledge of these electrical properties canlead to an understanding of the underlying basic biologicalprocesses. Indeed, biological impedance studies have longbeen important in electrophysiology and biophysics; one ofthe first demonstrations of the existence of the cell mem-brane was based on dielectric studies on cell suspensions(1).To analyze the response of a tissue to electric stimula-tion, we need data on the specific conductivities and rel-ative permittivities of the tissues or organs. A microscopicdescription of the response is complicated by the variety ofcell shapes and their distribution inside the tissue as wellas the different properties of the extracellular media.Therefore, a macroscopic approach is most often used tocharacterize field distributions in biological systems.Moreover, even on a macroscopic level, the electrical prop-erties are complicated. They can depend on the tissue ori-entation relative to the applied field (directionalanisotropy), the frequency of the applied field (the tissueis neither a perfect dielectric nor a perfect conductor), orthey can be time- and space-dependent (e.g., changes intissue conductivity during electropermeabilization).2. BIOLOGICAL MATERIALS IN AN ELECTRIC FIELDThe electrical properties of any material, including bio-logical tissue, can be broadly separated into two catego-ries: conducting and insulating. In a conductor, theelectric charges move freely in response to the applicationof an electric field, whereas in an insulator (dielectric), thecharges are fixed and not free to move. A more detaileddiscussion of the fundamental processes underlying theelectrical properties of tissue can be found in Foster andSchwan (2).If a conductor is placed in an electric field, charges willmove within the conductor until the interior field is zero.In the case of an insulator, no free charges exist, so netmigration of charge does not occur. In polar materials,however, the positive and negative charge centers in themolecules do not coincide. An electric dipole moment, p,issaid to exist. An applied field, E
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Cites background from "Electric properties of tissues"
...1) RC elements connected in series could be employed to model single limbs and limb leakages [23]....
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...like Cole–Davidson and Havrilak–Negami are used for nonbiological materials [23]....
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17 Jun 2014TL;DR: The working principles, applications, merits, and demerits of these methods has been discussed in detail along with their other technical issues followed by present status and future trends.
Abstract: Under the alternating electrical excitation, biological tissues produce a complex electrical impedance which depends on tissue composition, structures, health status, and applied signal frequency, and hence the bioelectrical impedance methods can be utilized for noninvasive tissue characterization. As the impedance responses of these tissue parameters vary with frequencies of the applied signal, the impedance analysis conducted over a wide frequency band provides more information about the tissue interiors which help us to better understand the biological tissues anatomy, physiology, and pathology. Over past few decades, a number of impedance based noninvasive tissue characterization techniques such as bioelectrical impedance analysis (BIA), electrical impedance spectroscopy (EIS), electrical impedance plethysmography (IPG), impedance cardiography (ICG), and electrical impedance tomography (EIT) have been proposed and a lot of research works have been conducted on these methods for noninvasive tissue characterization and disease diagnosis. In this paper BIA, EIS, IPG, ICG, and EIT techniques and their applications in different fields have been reviewed and technical perspective of these impedance methods has been presented. The working principles, applications, merits, and demerits of these methods has been discussed in detail along with their other technical issues followed by present status and future trends.
281 citations
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01 Feb 2010
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Abstract: Part I. Foundations: Ten chapters lay a foundation in device physics, noise, and feedback systems including nano scales in a highly original fashion, emphasizing intuitive thinking. This foundation is important in designing and analyzing ultra-low-power systems in both electronics and biology Part II. Low-Power Analog and Biomedical Circuits: Five chapters present building-block circuits that are useful for ultra-low-power biomedical electronics and analog electronic systems in general Part III. Low-Power RF and Energy-Harvesting Circuits for Biomedical Systems: Three chapters provide an in-depth description of energy-efficient power and data radio-frequency (RF) links that are fundamental to biomedical systems Part IV. Biomedical Electronic Systems: Two chapters provide an in-depth look at ultra-low-power implantable electronics and ultra-low-power noninvasive electronics for biomedical applications, respectively. Case studies for cochlear implants for the deaf, brain implants for the blind and paralyzed, wearable cardiac devices, and biomolecular sensing are provided Part V. Principles for Ultra-Low-Power Analog and Digital Design: Two chapters discuss principles for ultra-low-power digital design and ultra-low-power analog and mixed-signal design, respectively. The chapters identify ten fundamental principles that are common in both biology and electronics, analog and digital design Part VI. Bio-Inspired Systems: A chapter on neuromorphic electronics discusses electronics inspired by neurobiology followed by a chapter that discusses a novel form of electronics termed Cytomorphic Electronics, electronics inspired by cell biology. These chapters discuss applications of bio-inspired systems to engineering and medicine, deep connections between chemistry and electronics, and provide a unifying viewpoint of ultra-low-power design in biology and in electronics Part VII. Energy Sources: A chapter on batteries and electrochemistry discusses how batteries work from a unique circuit viewpoint. The last chapter discusses energy harvesting in biomedical systems at portable scales (vibration and body heat) and at larger scales (low-power cars and solar cells). Principles of low-power design are shown to extend from small scales in electronics to larger scales and to non-electrical systems. This book reveals the deep connections between energy use and energy generation, vital for sustainable energy systems of the future.
218 citations
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TL;DR: A flexible folded slot dipole implantable antenna operating in the Industrial, Scientific, and Medical (ISM) band (2.4-2.4835 GHz) for biomedical applications is presented in this paper.
Abstract: We present a flexible folded slot dipole implantable antenna operating in the Industrial, Scientific, and Medical (ISM) band (2.4-2.4835 GHz) for biomedical applications. To make the designed antenna suitable for implantation, it is embedded in biocompatible Polydimethylsiloxane (PDMS). The antenna was tested by immersing it in a phantom liquid, imitating the electrical properties of the human muscle tissue. A study of the sensitivity of the antenna performance as a function of the dielectric parameters of the environment in which it is immersed was performed. Simulations and measurements in planar and bent state demonstrate that the antenna covers the complete ISM band. In addition, Specific Absorption Rate (SAR) measurements indicate that the antenna meets the required safety regulations.
184 citations
Cites background from "Electric properties of tissues"
..., in the MHz range), the anisotropic properties disappear [28]....
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TL;DR: A comprehensive review of the body of knowledge concerning gene electrotransfer that has been accumulated over the last three decades is presented, with particular emphasis on DNA internalization and intracellular trafficking.
Abstract: Gene electrotransfer is a powerful method of DNA delivery offering several medical applications, among the most promising of which are DNA vaccination and gene therapy for cancer treatment. Electroporation entails the application of electric fields to cells which then experience a local and transient change of membrane permeability. Although gene electrotransfer has been extensively studied in in vitro and in vivo environments, the mechanisms by which DNA enters and navigates through cells are not fully understood. Here we present a comprehensive review of the body of knowledge concerning gene electrotransfer that has been accumulated over the last three decades. For that purpose, after briefly reviewing the medical applications that gene electrotransfer can provide, we outline membrane electropermeabilization, a key process for the delivery of DNA and smaller molecules. Since gene electrotransfer is a multipart process, we proceed our review in describing step by step our current understanding, with particular emphasis on DNA internalization and intracellular trafficking. Finally, we turn our attention to in vivo testing and methodology for gene electrotransfer.
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References
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TL;DR: Three experimental techniques based on automatic swept-frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz, demonstrating that good agreement was achieved between measurements using the three pieces of equipment.
Abstract: Three experimental techniques based on automatic swept-frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz. The technique used in conjunction with the impedance analyser is described. Results are given for a number of human and animal tissues, at body temperature, across the frequency range, demonstrating that good agreement was achieved between measurements using the three pieces of equipment. Moreover, the measured values fall well within the body of corresponding literature data.
3,996 citations
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TL;DR: A parametric model was developed to enable the prediction of dielectric data that are in line with those contained in the vast body of literature on the subject.
Abstract: 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.
3,985 citations
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TL;DR: The dielectric properties of tissues have been extracted from the literature of the past five decades and presented in a graphical format 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.
Abstract: 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.
2,932 citations
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TL;DR: The paper traces the history of, and tabulates determinations of the electrical resistivity of blood, other body fluids, cardiac muscle, skeletal muscle, lung, kidney, liver, spleen, pancreas, nervous tissue, fat, bone, and other miscellaneous tissues.
Abstract: The paper traces the history of, and tabulates determinations of the electrical resistivity of blood, other body fluids, cardiac muscle, skeletal muscle, lung, kidney, liver, spleen, pancreas, nervous tissue, fat, bone, and other miscellaneous tissues. Where possible, the conditions of measurement are given.
1,645 citations
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TL;DR: The classical principles behind dielectric relaxation are summarized, as empirical correlations with tissue water content in other compositional variables, and a comprehensive table is presented of dielectrics properties.
Abstract: We critically review bulk electrical properties of tissues and other biological materials, from DC to 20 GHz, with emphasis on the underlying mechanisms responsible for the properties. We summarize the classical principles behind dielectric relaxation and critically review recent developments in this field. Special topics include a summary of the significant recent advances in theories of counterion polarization effects, dielectric properties of cancer vs. normal tissues, properties of low-water-content tissues, and macroscopic field-coupling considerations. Finally, the dielectric properties of tissues are summarized as empirical correlations with tissue water content in other compositional variables; in addition, a comprehensive table is presented of dielectric properties. The bulk electrical properties of tissues are needed for many bioengineering applications of electric fields or currents, and they provide insight into the basic mechanisms that govern the interaction of electric fields with tissue.
1,337 citations