Biomedical Signals and Sensors III: Linking Electric Biosignals and Biomedical Sensors

PREFACE

ACKNOWLEDGEMENTS

SYMBOLS AND ABBREVIATIONS

SYMBOLS OF BIOSIGNALS

6             SENSING BY ELECTRIC BIOSIGNALS

6.1          Formation aspects

6.1.1               Permanent biosignals

6.1.2               Induced biosignals

6.1.3               Transmission of electric signals

6.1.3.1  Propagation of electric signals

6.1.3.1.1  Lossless medium

6.1.3.1.2  Lossy medium

6.1.3.2  Effects on electric signals

6.1.3.2.1     Volume effects

6.1.3.2.1.1.1    Electric and magnetic fields

6.1.3.2.1.1.2    Current density and current

6.1.3.2.1.1.3    Electric field and voltage

6.1.3.2.1.1.4    Electrical impedance

6.1.3.2.1.1.5    Simple tissue model

6.1.3.2.1.1.6    Mutual field coupling and quasi-electrostatic situation

6.1.3.2.1.2    Incident electric fields

6.1.3.2.1.2.1    Conductive phenomena

6.1.3.2.1.2.2    Polarization phenomena

6.1.3.2.1.2.3    Conductive versus polarization behaviour

6.1.3.2.1.2.4    Conductivity and polarization with relaxation and dispersion

6.1.3.2.1.2.5    Charge and current induction

6.1.3.2.1.3    Incident magnetic fields

6.1.3.2.1.4    Incident electromagnetic fields

6.1.3.2.2     Inhomogeneity effects

6.1.3.2.2.1    Boundary conditions

6.1.3.2.2.1.1    Conductive phenomena

6.1.3.2.2.1.2    Displacement phenomena

6.1.3.2.2.1.3    Conductive and displacement phenomena

6.1.3.2.2.1.4    Inhomogeneous structures and varying frequency

6.1.3.2.2.2    Diffraction

6.1.3.2.2.3    Reflection and refraction

6.1.3.2.3     Volume and inhomogeneity effects - a quantitative approach

6.1.3.2.3.1    Incindent electric field

6.1.3.2.3.1    Incident contact current

6.1.3.2.3.1    Incident magnetic field

6.1.3.2.4     Physiological effects

6.1.3.2.4.1    Stimulation effects

6.1.3.2.4.1.2    Charge transfer during stimulation

6.1.3.2.4.1.3    Stimulation pattern

6.1.3.2.4.1.3.1   Single monophasic stimulus

6.1.3.2.4.1.3.2   Single biphasic stimulus

6.1.3.2.4.1.3.3   Periodic stimulus

6.1.3.2.4.1.4    Strength-duration curve

6.1.3.2.4.1.5    Activating function

6.1.3.2.4.1.6    Cathodic and anodic stimulation

6.1.3.2.4.1.6.1   Cathodic block and stimulation upper threshold

6.1.3.2.4.1.6.2   Current-distance relationship

6.1.3.2.4.1.6.3   Numerical simulation - a quantitative approach

6.1.3.2.4.1.7    Axon thickness and its distance to electrode

6.1.3.2.4.1.8    Monopolar, bipolar, and tripolar modes

6.1.3.2.4.2    Thermal effects

6.1.3.2.5     Adverse health effects and exposure limits

6.1.3.2.5.1    Heart current factor

6.1.3.2.5.2    Neural stimulation

6.1.3.2.5.3    Effects of the direct current on tissue

6.2          Sensing and coupling of electric signals

6.2.1         Electrodes

6.2.1.1        Tissue, skin, and electrode effects

6.2.1.1.1     Tissue impedance

6.2.1.1.2     Skin impedance

6.2.1.1.3     Electrode polarization and impedance

6.2.1.1.3.1 Metal ion electrode and its double layer

6.2.1.1.3.1.1                Electrical double layer

6.2.1.1.3.1.2                Specific adsorption

6.2.1.1.3.1.3                Water relevance

6.2.1.1.3.1.4                Mass transfer

6.2.1.1.3.1.5                Electric potential and Debye length

6.2.1.1.3.1.6                Half-cell voltage

6.2.1.1.3.2 Redox electrode and its double layer

6.2.1.1.3.3 Reference Ag/AgCl electrode

6.2.1.1.3.4 Active current or voltage application between electrodes

6.2.1.1.3.4.1                Charge transfer and activation overvoltage

6.2.1.1.3.4.2                Diffusion and diffusion overvoltage

6.2.1.1.3.4.3                Coupled reactions and reaction overvoltage

6.2.1.1.3.4.4                Dynamics of electro-kinetic processes

6.2.1.1.3.4.5                Polarization of the electrode/tissue boundary

6.2.1.1.3.4.6                Direct voltage application

6.2.1.1.3.4.7                Alternating voltage application

6.2.1.1.3.4.7.1            High field frequency

6.2.1.1.3.4.7.2            Low field frequency

6.2.1.1.3.4.7.3            Medium field frequency

6.2.1.1.3.4.8                Ag/AgCl and Pt electrodes

6.2.1.1.3.4.8.1            Ag/AgCl electrodes

6.2.1.1.3.4.8.2            Pt electrodes

6.2.1.1.3.4.8.3            Recording versus stimulation

6.2.1.1.3.5 Electrode impedance model

6.2.1.1.3.5.1                Polarizable electrode

6.2.1.1.3.5.2                Non-polarizable electrode

6.2.1.1.3.5.3                Polarizable versus non-polarizable electrodes

6.2.1.1.3.6 Experimental issues

6.2.1.1.3.6.1                Measurement of tissue impedance

6.2.1.1.3.6.2                Tissue conductivity

6.2.1.1.3.6.3                Movement artefacts

6.2.1.1.3.6.4                Charge and discharge of monitoring electrodes

6.2.1.1.4     Whole-body impedance

6.2.1.2        Signal coupling in diagnosis and therapy

6.2.1.2.1     Diagnosis

6.2.1.2.2     Therapy

6.2.1.2.3     Non-contact diagnosis

6.2.2         Biosignal and interference coupling

6.2.2.1        Capacitive coupling of interference

6.2.2.2        Inductive coupling of interference

6.2.2.3        Biosignal coupling - voltage divider

6.2.2.4        Common-mode interference

6.2.2.5        Differential-mode interference

6.2.2.6        Inner body resistance

6.2.2.7        Electrode area

6.2.2.8        Countermeasures against interference

6.2.2.8.1     Shielding

6.2.2.8.2     Driven-right-leg circuit

6.2.2.8.3     Notch filter

6.2.2.8.4     Preamplifier

6.2.2.8.5     Length of electrode leads

6.2.2.9        Triboelectricity

6.2.3         Body area networks

References