Impedance surprises

<abstract xmlns="http://www.w3.org/1999/xhtml">Chronic venous insufficiency of the lower limbs is a disease which is caused by an increased blood pressure inside the veins of the leg and the resulting increase of the contained blood volume. This work focuses on developing a device which uses impedance plethysmography, also known as impedance phlebography, to obtain information about the blood volume in the lower leg and provides the possibility to measure the impedance semi contact-less, e.g. through compression stockings. Furthermore a real-time beat-to-beat interval detection algorithm was implemented. Finally, the function of the developed impedance measuring system and the whole system was verified by comparing it with a gold standard. In comparison to the conductive coupling, the system performed similarly. The analysis showed that the developed system is suitable for semi-capacitive IPG. The algorithm was implemented conservatively since it provided a good false-positive rate of 0 %, but only a moderate sensitivity of about 68 %. Reliable and continuous measurement of the pulse signal was only possible in periods of immobility.</abstract>

Development of a real-time, semi-capacitive impedance phlebography device

<abstract xmlns="http://www.w3.org/1999/xhtml">The impedance, capacitance and conductance of deionized water-glucose polar solution is measured by employing impedance spectroscopy and a quasi-oscillatory nature of variation with glucose content in the solution is observed. Such quasi-oscillatory nature is attributed to the randomly distributed water-water, water-glucose and glucose-glucose dipole interactions at the molecular level in the solution. A relevant analytical model is developed on the basis of such random distribution of the molecular dipoles and the experimental data agree well with those obtained from the theoretical model. The electrical parameters are measured in the frequency range of 100Hz to 4MHz for the volume fractions of glucose with respect to water in the range of 0.1 to 0.5. The impedance, capacitance and conductance are obtained to be in the range of 1.03 kΩ – 112 kΩ, 34.9 pF – 1.66 nF, and 8.95 μS – 52.9 μS respectively for the glucose volume fraction range considered.</abstract>

Investigating the quasi-oscillatory behavior of electrical parameters with the concentration of D-glucose in aqueous solution

<abstract xmlns="http://www.w3.org/1999/xhtml">There is a need for isolated current sources for use in selected bioimpedance measurement circuits. The requirement for good isolation is particularly important in medical settings because of safety concerns. A new circuit for producing voltage-controlled current is presented. Measurements have been made on a prototype and simulations have been done on a SPICE model. The presented circuit is an H-bridge where the output devices are the output photodiodes of high-linearity optocouplers. Five operational amplifiers, four high linearity optocouplers, and passive components are used. Output current capability is <italic>±</italic>35 μ<italic>A</italic> with an output impedance that is more than 1 <italic>M</italic> Ω. It is possible to achieve bandwidths above 1 <italic>MHz</italic> for small load impedances. This circuit is well suited for medical applications thanks to the isolation in the optocouplers.</abstract>

Optically isolated current source

<abstract xmlns="http://www.w3.org/1999/xhtml">The present study determines the effect of compression over bioimpedance of healthy soft tissue (<italic>in-vitro</italic> and <italic>in-vivo)</italic>. Electrical impedance spectroscopy (EIS) is a promising tissue characterization and tumor detection technique that uses tissue impedance or admittance to characterize tissue and identify tissue properties as well as cell structure. Variation in EIS measurements while applying pressure suggests that compression tends to affect soft tissue bioimpedance. Moreover, the displacements in tissue caused by applied compression may provide useful information about the structure and state of the tissue. Thus combining the changes to the electrical properties of tissue resulted by applied compression, with the changes in tissue displacements caused by applied compression, and consequently measuring the effect that electrical and mechanical properties have on each other, can be useful to identify tissue structure. In this study, multifrequency bioimpedance measurements were performed on <italic>in-vitro</italic> and <italic>in-vivo</italic> soft tissue at different pressure levels. Increasing compression on the <italic>in-vitro</italic> tissue results in an increase in both extracellular resistance and membrane capacitance while it causes a reduction in the intracellular resistance. However, as the compression over the <italic>in-vivo</italic> samples increases, the intracellular and extracellular resistance increase and the membrane capacitance decreases. The <italic>in-vivo</italic> measurements on human body are also tested on contra-lateral tissue sites and similar tissue impedance variation trends are observed in the contra-lateral sites of human body. The evidence from these tests suggests the possibility of using this EIS-Pressure combined measurement method to improve tumor detection in soft tissue. Based upon the observations, the authors envision developing an advanced model based upon the Cole model, which is dependent on tissue displacements.</abstract>

Compression-dependency of soft tissue bioimpedance for <italic>in-vivo</italic> and <italic>in-vitro</italic> tissue testing

<abstract xmlns="http://www.w3.org/1999/xhtml">Impedance measurements that involve the human body are affected by the capacitance between the body and earth ground. This paper describes a fast method to estimate that capacitance at 10 kHz, which is valid for impedance analyzers intended to measure ungrounded impedances. The method does not require any external component other than two common capacitors and two conductive electrodes in contact with the body.</abstract>

A fast method to estimate body capacitance to ground at mid frequencies

<abstract xmlns="http://www.w3.org/1999/xhtml">Electrical Impedance Tomography (EIT) has been proposed as a method for imaging and localising epileptic activity in the brain. No existing EIT system meets all of the requirements for effective imaging of epilepsy. A parallel EIT system, employing frequency division multiplexing, is described, which is optimised for measuring impedance changes during epilepsy. The system is capable of imaging short duration, spontaneous events in a saline filled tank, using as little as 1ms of recorded data. In-vivo impedance measurements recorded during epilepsy in a rat model are presented.</abstract>

Parallel, multi frequency EIT measurement, suitable for recording impedance changes during epilepsy

<abstract xmlns="http://www.w3.org/1999/xhtml">We present a novel method to detect proximal volume changes based on the impedance plethysmogram (IPG) measured from limb to limb with two electrode pairs symmetrically placed at distal areas of the upper or the lower limbs. Since the measurement is sensitive to changes along the whole current path, this method allows us to detect changes in arteries that are more proximal to the torso than the measurement sites. Our results show that the Pulse Arrival Time (PAT) measured from the R peak of the ECG to the hand-to-hand IPG is close to the PAT to the elbow whereas the PAT measured from the R peak of the ECG to the foot-to-foot IPG is close to the PAT to the knee. This opens new avenues for noninvasive cardiovascular measurements based only on electrodes in contact with hands or feet.</abstract>

A novel method to obtain proximal plethysmographic information from distal measurements using the impedance plethysmogram

<abstract xmlns="http://www.w3.org/1999/xhtml">Alternating current methods have the potential to improve the measurement of electrodermal activity. However, there are pitfalls that should be avoided in order to perform these measurements in a correct manner. In this paper, we address issues like the choice of measurement frequency, placement of electrodes and the kind of electrodes used. Ignoring these factors may result in loss of measurement sensitivity or erroneous measurements with artifacts that contain little or no physiological information.</abstract>

Sources of error in AC measurement of skin conductance

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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 and educational material within all aspects of electrical bioimpedance are published.  The JoEB was established in 2010 by the Oslo Bioimpedance Group in Norway, as a specialized channel for publications related to the passive electrical properties of biomaterials. It has since been maintained as a not-for-profit journal with the main intention of offering new and established researchers in the field an easily accessible source of information.  We accept a wide range of papers that are related to electrical bioimpedance. Our aim is to cover the theory, experiments and applications that will typically be of interest to international bioimpedance students and researchers. Examples of relevant scientific topics can be (but are not limited to):   Impedance spectroscopy studies on biomaterials as basic research or to develop a new method related to that particular material. Studies where single- or multi-frequency bioimpedance measurements are used for monitoring of physiological parameters. Studies related to electrical impedance tomography (EIT). Instrumentation, algorithms, new applications, etc. Instrumentation or new measuring methods for bioimpedance measurements or EIT. Theoretical work related to bioimpedance. Modeling and simulations. Please note that simulations, e.g. by using the finite element method, should normally be validated through experiments before publishing. Studies on other sensor technologies that are relevant to bioimpedance (e.g. potentially in a multi-sensor solution) but where bioimpedance methods are not directly used. Non-linear (e.g. memristive) electrical properties of biomaterials.  Journal Metrics  Cite Score = 2.5 SJR = 0.436 SNIP = 0.978 Index Copernicus = 121.24  Publication Fee  JoEB is a non-profit journal and we only charge a publication fee to cover our direct publication costs. All the editorial functions are based on voluntary work. The article processing charges (APCs) are currently 400 Euro, there is no article submission charges. No other charges apply.  Archiving  Sciendo archives the contents of this journal in Portico - digital long-term preservation service of scholarly books, journals and collections.  Plagiarism Policy  The editorial board is participating in a growing community of Similarity Check System's in order to ensure that the content published is original and trustworthy. Similarity Check is a medium that allows for comprehensive manuscripts screening, aimed to eliminate plagiarism and provide a high standard and quality peer-review process. 

Journal of Electrical Bioimpedance

Volume 6 (2015): Issue 1 (January 2015)

Editorials

Impedance surprises

Articles