<abstract><title style='display:none'>Abstract</title>Under an alternating electrical signal, biological tissues produce a complex electrical bioimpedance that is a function of tissue composition and applied signal frequencies. By studying the bioimpedance spectra of biological tissues over a wide range of frequencies, we can noninvasively probe the physiological properties of these tissues to detect possible pathological conditions. Electrical impedance spectroscopy (EIS) can provide the spectra that are needed to calculate impedance parameters within a wide range of frequencies. Before impedance parameters can be calculated and tissue information extracted, impedance spectra should be processed and analyzed by a dedicated software program. National Instruments (NI) Inc. offers LabVIEW, a fast, portable, robust, user-friendly platform for designing data-analyzing software. We developed a LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) to analyze the electrical impedance spectra for tissue characterization in medical, biomedical and biological applications. Here, we test, calibrate and evaluate the performance of LEBISDI on the impedance data obtained from simulation studies as well as the practical EIS experimentations conducted on electronic circuit element combinations and the biological tissue samples. We analyze the Nyquist plots obtained from the EIS measurements and compare the equivalent circuit parameters calculated by LEBISDI with the corresponding original circuit parameters to assess the accuracy of the program developed. Calibration studies show that LEBISDI not only interpreted the simulated and circuit-element data accurately, but also successfully interpreted tissues impedance data and estimated the capacitive and resistive components produced by the compositions biological cells. Finally, LEBISDI efficiently calculated and analyzed variation in bioimpedance parameters of different tissue compositions, health and temperatures. LEBISDI can also be used for human tissue impedance analysis for electrical impedance-based tissue characterization, health analysis and disease diagnosis.</abstract>

A LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) for biological tissue impedance analysis and equivalent circuit modelling

<abstract><title style='display:none'>Abstract</title>Rapid development in the field of tissue engineering necessitates implementation of monitoring methods for evaluation of the viability and characteristics of the cell cultures in a real-time, non-invasive and non-destructive manner. Current monitoring techniques are mainly histological and require labeling and involve destructive tests to characterize cell cultures. Bioimpedance measurement technique which benefits from measurement of electrical properties of the biological tissues, offers a non-invasive, label-free and real-time solution for monitoring tissue engineered constructs. This review outlines the fundamentals of bioimpedance, as well as electrical properties of the biological tissues, different types of cell culture constructs and possible electrode configuration set ups for performing bioimpedance measurements on these cell cultures. In addition, various bioimpedance measurement techniques and their applications in the field of tissue engineering are discussed.</abstract>

Applications of bioimpedance measurement techniques in tissue engineering

<abstract><title style='display:none'>Abstract</title>An electrical Impedance based tool is designed and developed to aid physicians performing clinical exams focusing on cancer detection. Current research envisions improvement in sensor-based measurement technology to differentiate malignant and benign lesions in human subjects. The tool differentiates malignant anomalies from nonmalignant anomalies using Electrical Impedance Spectroscopy (EIS). This method exploits cancerous tissue behavior by using EIS technique to aid early detection of cancerous tissue.The correlation between tissue electrical properties and tissue pathologies is identified by offering an analysis technique based on the Cole model. Additional classification and decision-making algorithm is further developed for cancer detection. This research suggests that the sensitivity of tumor detection will increase when supplementary information from EIS and built-in intelligence are provided to the physician.</abstract>

Cancer detection based on electrical impedance spectroscopy: A clinical study

<abstract><title style='display:none'>Abstract</title>This article presents an overview of rheoencephalography (REG) – electrical impedance measurements of the brain – and summarizes past and ongoing research to develop medical applications of REG for neuro-critical care and for primary prevention of stroke and cardiovascular disease. The availability of advanced electronics and computation has opened up the potential for use of REG technology as a noninvasive, continuous and inexpensive brain monitor for military and civilian applications. The clinical background information presented here introduces physiological and clinical environments where REG has potential for use in research and clinical settings.REG studies over the past three decades have involved in vitro and in vivo groups (animal and human), including more than 1500 measurements and related electronic and computational results and practical applications. In vitro studies helped researchers understand the flow/volume relationship between Doppler ultrasound and electrical impedance signals and supported development of REG data processing methods. In animal studies, REG was used to monitor the lower limit of cerebral blood flow (CBF) autoregulation (AR) using a newly developed algorithm. These animal studies also confirmed correlations between REG and measurements of carotid flow (CF) and intracranial pressure (ICP). Human studies confirmed the applicability of REG for detecting cerebrovascular alteration, demonstrating the usefulness of REG in the field of stroke/cardio-vascular disease prevention. In these studies, REG was compared to known stroke risk factors and to results obtained using carotid ultrasound measurements. An intelligent REG system (Cerberus) has been developed for primary stroke prevention. In these studies, the biologically relevant variables of the REG signal were pulse amplitude (minimum – maximum distance) and duration of the anacrotic (rising) portion of the REG pulse wave.The principal limitation of REG for clinical application is the lack of pathological and physiological correlations. The studies presented here have initiated such inquiries, but many clinical questions about the pathophysiological background of REG remain unanswered.These results demonstrate that REG development is a multidisciplinary subject with relevance for medicine (vascular neurology and neurosurgery intensive care); electronic engineering; mathematics, and computer science (data processing). It is hoped that information presented in this article will provide assistance to those involved in REG research, particularly in development and clinical applications.</abstract>

Studies in Rheoencephalography (REG)

<abstract><title style='display:none'>Abstract</title>Bioimpedance measurement systems often use the Howland current sources to excite the biological material under study. Usually, difference or instrumentation amplifiers are used to measure the resulting voltage drop on this material. In these circuits, common mode voltage appears as artifacts in the measurement. Most researches on current sources are focused on improving the output impedance, letting other characteristics aside. In this paper, it is made a brief review on the load common mode voltage and output swing of various topologies of Howland current sources. Three circuits are proposed to reduce load common mode voltage and enhance load capability by using a fully differential amplifier as active component. These circuits are equated, simulated and implemented. The three proposed circuits were able to deliver an output current with cut-off frequency (-3dB) higher than 1 MHz for loads as big as 4.7 kΩ. The worst measured load common mode voltage was smaller than 24 mV for one of the circuits and smaller than 8 mV for the other two. Consequently, it could be obtained increases in the Common Mode Rejection Ratio (CMRR) up to 60 dB when compared to the Enhanced Howland Current Source (EHCS).</abstract>

Design of current sources for load common mode optimization

<abstract><title style='display:none'>Abstract</title>In recent years several electrical wound management systems, so called electroceuticals, have been introduced claiming an induced electrical response in the wounded tissue. Some have external current and voltage sources while others have internal constructions aiming at creating necessary therapeutic currents. We investigate two representative electroceuticals by mapping out their electrical field landscapes using a previously developed skin model within a numerical simulation scheme. We find very strong fields from the electroceuticals of the order of 1 kV/m amenable for electrotaxic influence on pertinent cell types for wound healing. Current densities can locally be as high as 1 A/cm2.</abstract>

Electrical field landscape of two electroceuticals

<abstract>
<title style='display:none'>Abstract</title>
The Focused Impedance Method (FIM) is a new technique of electrical bioimpedance measurements in the human body. The idea originated in Bangladesh and provides an opportunity for localized measurement of bioimpedance down to reasonable depths from the body surface using skin surface electrodes. This has potential applications for physiological studies of targeted organs in the body and in detecting or diagnosing diseases and disorders. FIM is based on the age-old Tetra-Polar Impedance Measurement (TPIM) but provides a few significant improvements.
Technology must be developed indigenously to obtain long-term benefits, particularly in Low and Medium Income countries (LMIC). This paper presents an experimental sensitivity study of the six-electrode version of the Focused Impedance method (FIM-6) with the circuit and phantom indigenously designed in Nepal. The work involved sensitivity studies of both FIM-6 and TPIM with the necessary circuit blocks developed through experimental validation. The sensitivity studies were performed on a simple 2D phantom with different electrode arrangements for FIM-6 and linear TPIM. A cylindrical object was placed at different positions for this study. The FIM-6 gave a high sensitivity in the central part, which remained almost constant within a small region that may be termed as the focused region. On the other hand, TPIM results fell off sharply away from the central point, making it unsuitable for practical measurements on target organs. Besides, there were areas with large negative sensitivities in TPIM, which were much smaller in FIM. The results obtained through this work clearly show the improvement offered by FIM over TPIM.
</abstract>

Sensitivity study of a locally developed six electrode focused impedance method

<abstract>
<title style='display:none'>Abstract</title>
In the last decades there is a growing interest in the evaluation of human body composition for being an important part of the integral assessment of individuals. Its use has been extended to different disciplines associated with health care (medicine, nutrition, physiotherapy), and to sports and population fields. Specifically, fat percentage can be related to innumerable diseases. However, there are discrepancies in the results of fat percentage measurement measured by different methods.
<sec>
<title style='display:none'>Objective</title>
To evaluate the concordance between two low-cost and easily accessible double indirect methods, which have been used indistinctly in different studies where access to more accurate methods is not available, and to determine fat percentage and its relationship with age, sex, body mass index (BMI), waist circumference, level of physical activity and sedentary hours.
</sec>
<sec>
<title style='display:none'>Materials and Method</title>
Twenty-four persons between 18 and 38 years and 28 between 39 and 59 years from a university community were evaluated. Calculations were made: BMI, fat % was estimated by anthropometry with a digital adipometer (Skyndex System I USA) and by Electrical Bioimpedance Analysis – BIA (Biody Expert ZM II FRA), physical activity level and sedentary hours were determined with the short IPAQ questionnaire. Pearson's correlation coefficient, Bland &amp; Altman's graphical method and Lin's concordance correlation index were calculated. The significance level p&lt;0.05 was estimated.
</sec>
<sec>
<title style='display:none'>Results</title>
The fat percentage by anthropometry was: 30.5% ±8.5 (18–38 years) 35.0% ±6.7 (39–59 years); by BIA 27.0% ±7.3 (18–38 years) and 29.2% ±7.0 (39–59 years). Both techniques showed good correlation, but low degree of concordance (Lin index less than 0.9) except for the group of young persons with moderate level of physical activity (0.95).
</sec>
<sec>
<title style='display:none'>Conclusions</title>
The doubly indirect methods used in the study showed strong correlation, but low concordance, so their use is not recommended indistinctly for the follow-up of a particular case. According to the study data for this specific population in young people with moderate physical activity, follow-up could be performed with either of the two methods.
</sec>
</abstract>

Concordance between dual indirect methods for assessing fat percentage

<abstract>
<title style='display:none'>Abstract</title>
In neurocritical care, the gold standard method is intracranial pressure (ICP) monitoring for the patient's lifesaving. Since it is an invasive method, it is desirable to use an alternative, noninvasive technique. The computerized real-time invasive cerebral blood flow (CBF) autoregulation (AR) monitoring calculates the status of CBF AR, called the pressure reactivity index (PRx). Studies documented that the electrical impedance of the head (Rheoencephalography – REG) can detect the status of CBF AR (REGx) and ICP noninvasively. We aimed to test REG to reflect ICP and CBF AR.
For nineteen healthy subjects we recorded bipolar bifrontal and bitemporal REG derivations and arm bioimpedance pulses with a 200 Hz sampling rate. The challenges were a 30-second breath-holding and head-down-tilt (HDT – Trendelenburg) position. Data were stored and processed offline. REG pulse wave morphology and REGx were calculated.
The most relevant finding was the significant morphological change of the REG pulse waveform (2nd peak increase) during the HDT position. Breath-holding caused REG amplitude increase, but it was not significant. REGx in male and female group averages have similar trends during HDT by indicating the active status of CBF AR.
The morphological change of REG pulse wave during HDT position was identical to ICP waveform change during increased ICP, reflecting decreased intracranial compliance. A correlation study between ICP and REG was initiated in neurocritical care patients. The noninvasive REG monitoring would also be useful in space research as well as in military medicine during the transport of wounded service members as well as for fighter pilots to indicate the loss of CBF and consciousness.
</abstract>

Rheoencephalography: A non-invasive method for neuromonitoring

<abstract>
<title style='display:none'>Abstract</title>
Moisturizers are cosmetic compounds designed to increase the moisture content of the skin. There are many types of these products in the market making it difficult for consumers to select the most effective moisturizer according to their age and gender. Hence, the aim of this study was to evaluate the effects of different moisturizers on skin hydration as well as to figure out any dependencies of the effects of these products on age or gender-related differences. We investigated the short-term moisturizing effects of five different skin moisturizers on 60 participants by using a low frequency electrical instrument. Skin surface susceptance was recorded and compared before and after the application of moisturizers. Statistically significant differences were observed in the moisturizing effect among different types of products. However, with respect to gender and age differences, there were insignificant differences in the effects of the moisturizers. Results of this study suggest that some types of moisturizers that exist in the markets are not as effective as required, which calls for a further evaluation of the moisturizers before entering markets and offering them for sale. In addition, findings suggest that gender or age differences are perhaps not important to consider in the application of moisturizers.
</abstract>

Evaluation of the effect of several moisturizing creams using the low frequency electrical susceptance approach

Electrical bioimpedance in the era of artificial intelligence

<abstract>
<title style='display:none'>Abstract</title>
Biomedical engineering stands at the forefront of medical innovation, with electroencephalography (EEG) signal analysis providing critical insights into neural functions. This paper delves into the utilization of EEG signals within the MILimbEEG dataset to explore their potential for machine learning-based task recognition and diagnosis. Capturing the brain’s electrical activity through electrodes 1 to 16, the signals are recorded in the time-domain in microvolts. An advanced feature extraction methodology harnessing Hjorth Parameters—namely Activity, Mobility, and Complexity—is employed to analyze the acquired signals. Through correlation analysis and examination of clustering behaviors, the study presents a comprehensive discussion on the emergent patterns within the data. The findings underscore the potential of integrating these features into machine learning algorithms for enhanced diagnostic precision and task recognition in biomedical applications. This exploration paves the way for future research where such signal processing techniques could revolutionize the efficiency and accuracy of biomedical engineering diagnostics.
</abstract>

Advancing biomedical engineering: Leveraging Hjorth features for electroencephalography signal analysis

<abstract><title style='display:none'>Abstract</title>This paper is concerned with a physical model of an interdigitated sensor working in a frequency range from 100 Hz to 10 MHz. A theoretical approach is proposed to optimize the use of the sensor for bioimpedance spectroscopy. The correlation between design parameters and frequency behavior in coplanar impedance sensors are described. CoventorWare® software was used to model the biological medium loaded interdigital sensor in three dimensions to measure its electrical impedance. Complete system simulation by a finite element method (FEM) was used for sensor sensitivity optimization. The influence of geometrical parameters (number of fingers, width of the electrodes) on the impedance spectroscopy of the biological medium was studied. The simulation results are in agreement with the theoretical equations of optimization. Thus, it is possible to design <italic>a priori</italic> such sensor by taking into account the biological medium of interest that will load the sensor.</abstract>

Geometric parameters optimization of planar interdigitated electrodes for bioimpedance spectroscopy

<abstract><title style='display:none'>Abstract</title>Impedance cardiography (ICG) is a branch of bioimpedance primarily concerned with the determination of left ventricular stroke volume (SV). As implemented, using the transthoracic approach, the technique involves applying a current field longitudinally across a segment of thorax by means of a constant magnitude, high frequency, low amplitude alternating current (AC). By Ohm’s Law, the voltage difference measured within the current field is proportional to the electrical impedance Z (Ω). Without ventilatory or cardiac activity, Z is known as the transthoracic, static base impedance Z0. Upon ventricular ejection, a characteristic time dependent cardiac-synchronous pulsatile impedance change is obtained, ΔZ(t), which, when placed electrically in parallel with Z0, constitutes the time-variable total transthoracic impedance Z(t). ΔZ(t) represents a dual-element composite waveform, which comprises both the radially-oriented volumetric expansion of and axially-directed forward blood flow within both great thoracic arteries. In its majority, however, ΔZ(t) is known to primarily emanate from the ascending aorta. Conceptually, commonly implemented methods assume a volumetric origin for the peak systolic upslope of ΔZ(t), (i.e. dZ/dtmax), with the presumed units of Ω·s–1. A recently introduced method assumes the rapid ejection of forward flowing blood in earliest systole causes significant changes in the velocity-induced blood resistivity variation (Δρb(t), Ωcm·s–1), and it is the peak rate of change of the blood resistivity variation dρb(t)/dtmax (Ωcm·s–2) that is the origin of dZ/dtmax. As a consequence of dZ/dtmax peaking in the time domain of peak aortic blood acceleration, d<italic>v</italic>/dtmax (cm·s–2), it is suggested that dZ/dtmax is an ohmic mean acceleration analog (Ω·s–2) and not a mean flow or velocity surrogate as generally assumed. As conceptualized, the normalized value, dZ/dtmax/Z0, is a dimensionless ohmic mean acceleration equivalent (s–2), and more precisely, the electrodynamic equivalent of peak aortic reduced average blood acceleration (PARABA, d&lt;v&gt;/dtmax/R, s–2). As necessary for stroke volume calculation, dZ/dtmax/Z0 must undergo square root transformation to yield an ohmic mean flow velocity equivalent. To compute SV, the square root of the dimensionless ohmic mean acceleration equivalent ([dZ/dtmax/Z0]0.5, s–1) is multiplied by a volume of electrically participating thoracic tissue (VEPT, mL) and left ventricular ejection time (TLVE, s). To find the bulk volume of the thoracic contents (i.e. VEPT), established methods implement exponential functions of measured thoracic length (L(cm)n) or height-based thoracic length equivalents (0.01×%H(cm)n). The new method conceptualizes VEPT as the intrathoracic blood volume (ITBV, mL), which is approximated through allometric equivalents of body mass (aMb). In contrast to the classical two-element parallel conduction model, the new method comprises a three-compartment model, which incorporates excess extra-vascular lung water (EVLW) as a component of both Z0 and VEPT. To fully appreciate the evolution and analytical justification for impedance-derived SV equations, a review of the basics of pulsatile blood flow is in order.</abstract>

Impedance cardiography: Pulsatile blood flow and the biophysical and electrodynamic basis for the stroke volume equations

<abstract><title style='display:none'>Abstract</title>Using the fractional calculus approach, we present the Laplace analysis of an equivalent electrical circuit for a multilayered system, which includes distributed elements of the Cole model type. The Bode graphs are obtained from the numerical simulation of the corresponding transfer functions using arbitrary electrical parameters in order to illustrate the methodology. A numerical Laplace transform is used with respect to the simulation of the fractional differential equations. From the results shown in the analysis, we obtain the formula for the equivalent electrical circuit of a simple spectrum, such as that generated by a real sample of blood tissue, and the corresponding Nyquist diagrams. In addition to maintaining consistency in adjusted electrical parameters, the advantage of using fractional differential equations in the study of the impedance spectra is made clear in the analysis used to determine a compact formula for the equivalent electrical circuit, which includes the Cole model and a simple RC model as special cases.</abstract>

Modeling and Simulation of Equivalent Circuits in Description of Biological Systems - A Fractional Calculus Approach

<abstract><title style='display:none'>Abstract</title>Lab-on-chip systems (LOCs) can be used as <italic>in vitro</italic> systems for cell culture or manipulation in order to analyze or monitor physiological cell parameters. LOCs may combine microfluidic structures with integrated elements such as piezo-transducers, optical tweezers or electrodes for AC-electrokinetic cell and media manipulations. The wide frequency band (&lt;1 kHz to &gt;1 GHz) usable for AC-electrokinetic manipulation and characterization permits avoiding electrochemical electrode processes, undesired cell damage, and provides a choice between different polarization effects that permit a high electric contrast between the cells and the external medium as well as the differentiation between cellular subpopulations according to a variety of parameters. It has been shown that structural polarization effects do not only determine the impedance of cell suspensions and the force effects in AC-electrokinetics but can also be used for the manipulation of media with inhomogeneous temperature distributions. This manuscript considers the interrelations of the impedance of suspensions of cells and AC-electrokinetic single cell effects, such as electroorientation, electrodeformation, dielectrophoresis, electrorotation, and travelling wave (TW) dielectrophoresis. Unified models have allowed us to derive new characteristic equations for the impedance of a suspension of spherical cells, TW dielectrophoresis, and TW pumping. A critical review of the working principles of electro-osmotic, TW and electrothermal micropumps shows the superiority of the electrothermal pumps. Finally, examples are shown for LOC elements that can be produced as metallic structures on glass chips, which may form the bottom plate for self-sealing microfluidic systems. The structures can be used for cell characterization and manipulation but also to realize micropumps or sensors for pH, metabolites, cell-adhesion, etc.</abstract>

A short tutorial contribution to impedance and AC-electrokinetic characterization and manipulation of cells and media: Are electric methods more versatile than acoustic and laser methods?

<abstract><title style='display:none'>Abstract</title>A Projection Error Propagation-based Regularization (PEPR) method is proposed and the reconstructed image quality is improved in Electrical Impedance Tomography (EIT). A projection error is produced due to the misfit of the calculated and measured data in the reconstruction process. The variation of the projection error is integrated with response matrix in each iteration and the reconstruction is carried out in EIDORS. The PEPR method is studied with the simulated boundary data for different inhomogeneity geometries. Simulated results demonstrate that the PEPR technique improves image reconstruction precision in EIDORS and hence it can be successfully implemented to increase the reconstruction accuracy in EIT.</abstract>

Improving Image Quality in Electrical Impedance Tomography (EIT) Using Projection Error Propagation-Based Regularization (PEPR) Technique: A Simulation Study

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Journal of Electrical Bioimpedance

 The Journal of Electrical Bioimpedance (JoEB) is an international, single blind peer reviewed, fast publication, non-commercial, open access journal. Original research papers, review articles,...

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 The Journal of Electrical Bioimpedance (JoEB) is an international, single blind peer reviewed, fast publication, non-commercial, open access journal....