Bioelectricity measurement

The classic models for bioimpedance and bioelectricity are mathematical equations and equivalent circuit diagrams with the same electrical behavior as the tissue to be modeled. Others include statistical models, which are used to determine the correspondence between bioelectrical measurements and physiological variables (e.g., tissue characterization). 

Some changes and additions have been made in this edition An electrode is the most important component of any bioimpedance and bioelectric measuring systems. To make the book easier to read, we have dedicated a specific chapter to electrodes. Furthermore, we have extended the chapter on models with a comprehensive tutorial on statistical analysis of bioimpedance data. We have also included the Kelvin probe, memristor theory, and the concept of universality (scaling properties) and we have expanded the survey on impedance analyzers. 

Lukaski H, Johnson E, Bolonchuk W et al (1985) Assessment impedance of fat-fi ee mass using bioelectrical measurements of the human body. Am 1 Clin Nutr 41 810-7 Fleiss 1 (1986) The design and analysis of clinical experiments. Wiley, New York DOI 10.1016/0898-1221(87)90245-8 Bland J, Altman D (1986) Statistical methods for assessing agreement between two methods of clinical measurement Lancet 1 307-10... 

The key parameter concerning the electromagnetic induction to the bioelectric measurement system is dB/dt where B is magnetic field generated by a TMS coil. The parameter dB/dt is proportional to di/dt, thus the key parameter is proportional to Vl. 

Fig. 1 in the right side shows the equivalent circuit model of the bioelectric measurement system. This circuit is considered to form the closed circuit by the bioelectric equivalent circuit and the measurement system, which causes the electromagnetic induction fl om the TMS coil. The resistance component Rb and the capacitance component Q denote the bioelectric equivalent circuit, and an electrical potential of EEG is assumed to measure the terminal voltage of the Cb, named Vcb- The reason of using simpler bioelectric equivalent circuit is to form the solvable circuit equation and to get the solution. 

The transformer to describe coupling of the electromagnetic induction is replaced by following simple description. Namely, when the terminal voltage of the inductance component L in the TMS coil is Vl, the induced electromotive force is driven to the bioelectric measurement system as shown in the Fig. 1, where is a proportional factor. Furthermore, it is assumed that the coupling influence from the bioelectric measurement system to the TMS equipment is negligible, and TMS affects to the human body only in the oscillation mode. 

The state transition of the bioelectric measurement system depends on that of the TMS equipment system. In the LCr oscillation mode (SW2=ON), the bioelectric measurement system is driven by the induced electromotive force from the TMS coil. In the discharge mode (SW3=ON), the influence from the TMS coil is negligible, and RbCb decay is occurred by consuming the energy left in the capacitance component Cb. 

One of the main determinants of the number of subjects required to reach the desired statistical power is the precision of the measurement tool utilized. More precise measurements will reduce the number of subjects required. As an example, if a study is being conducted to assess the influence of a dietary supplement on body fat, several measurement tools could be used to assess this outcome. These tools range from low levels of cost and precision (e.g. skinfold measurements) to moderate levels (e.g. bioelectrical impedance) to high levels of cost and precision (dual x-ray absorptiometry - DXA). A study that uses skinfold measurements to measure the outcome will require many more subjects than one which employs DXA. Therefore, it is often less expensive in total to utilize a more expensive measurement tool, because the more precise tool will allow the study to have sufficient power with a smaller number of subjects. 

Anthropometric measurements are gross measurements of body cell mass used to evaluate LBM and fat stores. The most common measurements are weight, height, limb size (e.g., skinfold thickness and midarm muscle, wrist, and waist circumferences), and bioelectrical impedance analysis (BIA). 

The rat skin TER assay enables to reliably discriminate between skin corrosives and noncorrosive substances [148], The assay relies on the change in the bioelectrical properties of the skin in response to the application of test chemicals. For the measurements, small discs of rat skin are necessary onto which the substances are applied to the epidermal surface for up to 24 h. In... 

Several methods are available to evaluate a patient s actual body composition rather than total body mass. Skin-fold measurement may be of value in evaluating subcutaneous adiposity (adipose tissue accumulation) proper technique is required for reliable results. Other anthropomorphic measurements such as bioelectrical impedance, dual-energy x-ray absorptiometry, and total body water immersion are also available.These last techniques are often of value in research studies, but it is clinically impractical to use them routinely (Elberg et al., 2004). 

KdBlinger, C., Drost, S., Aberl, F., Wolf, H., Koch, S., and Woias, P. (1992). A quartz crystal biosensor for measurement in liquids. Biosens. Bioelectr, 1, 397-404. 

With the above-mentioned diffusion coefficients the modeled delay of the molecule arrival at the receptor cell is about 10 ms after adsorption at the olfactory hairs (Kaissling 2001, Figure 3.7B). This fits to the minimum delay of the receptor potential, the first bioelectrical response of the receptor neuron, as measured after stimuli of high intensity. At weak stimulation the average delay of the responses is a few hundred ms due to the chemical reactions of the stimulus molecules including their interaction with the receptor molecules (Kaissling 2001, and unpubl.). 

Reid, B., Nuccitelli, R and Zhao, M. (2007) Non-invasive measurement of bioelectric currents with a vibrating probe. Nat. Protoc. 2, 661-669. 

The first is the Dirichlet condition, which says that one has a set of discrete measurements of the voltage of a subset of the outer surface. The second is the natural Neumann condition. While it does not look much different from the formulation of the direct problem, the inverse formulations are ill-posed. The bioelectric inverse problem in terms of primary current sources does not have a unique solution, and the solution does not depend continuously on the data. Thus, to obtain useful solutions, one must try to... 

Measurement of the Biomagnetic Signals Independence of Bioelectric and Biomagnetic Signals... 

L. A. Geddes, Electrodes and the Measurement of Bioelectric Events, Wiley-Interscience, New York (1972). 

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