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Sample records for electrical impedance scanning

  1. Noncontact scanning electrical impedance imaging.

    PubMed

    Liu, Hongze; Hawkins, Aaron; Schultz, Stephen; Oliphant, Travis E

    2004-01-01

    We are interested in applying electrical impedance imaging to a single cell because it has potential to reveal both cell anatomy and cell function. Unfortunately, classic impedance imaging techniques are not applicable to this small scale measurement due to their low resolution. In this paper, a different method of impedance imaging is developed based on a noncontact scanning system. In this system, the imaging sample is immersed in an aqueous solution allowing for the use of various probe designs. Among those designs, we discuss a novel shield-probe design that has the advantage of better signal-to-noise ratio with higher resolution compared to other probes. Images showing the magnitude of current for each scanned point were obtained using this configuration. A low-frequency linear physical model helps to relate the current to the conductivity at each point. Line-scan data of high impedance contrast structures can be shown to be a good fit to this model. The first two-dimensional impedance image of biological tissues generated by this technique is shown with resolution on the order of 100 mum. The image reveals details not present in the optical image. PMID:17271930

  2. Non-contact scanning electrical impedance imaging.

    PubMed

    Liu, Hongze; Hawkins, Aaron; Schultz, Stephen; Oliphant, Travis

    2004-01-01

    We are interested in applying electrical impedance imaging to a single cell because it has potential to reveal both cell anatomy and cell function. Unfortunately, classic impedance imaging techniques are not applicable to this small scale measurement due to their low resolution. In this paper, a different method of impedance imaging is developed based on a non-contact scanning system. In this system, the imaging sample is immersed in an aqueous solution allowing for the use of various probe designs. Among those designs, we discuss a novel shield-probe design that has the advantage of better signal-to-noise ratio with higher resolution compared to other probes. Images showing the magnitude of current for each scanned point were obtained using this configuration. A low-frequency linear physical model helps to relate the current to the conductivity at each point. Line-scan data of high impedance contrast structures can be shown to be a good fit to this model. The first two-dimensional impedance image of biological tissues generated by this technique is shown with resolution on the order of 100 mum. The image reveals details not present in the optical image. PMID:17271931

  3. Advances in imaging and quantification of electrical properties at the nanoscale using Scanning Microwave Impedance Microscopy (sMIM)

    NASA Astrophysics Data System (ADS)

    Friedman, Stuart; Yang, Yongliang; Amster, Oskar

    2015-03-01

    Scanning Microwave Impedance Microscopy (sMIM) is a mode for Atomic Force Microscopy (AFM) enabling imaging of unique contrast mechanisms and measurement of local permittivity and conductivity at the 10's of nm length scale. Recent results will be presented illustrating high-resolution electrical features such as sub 15 nm Moire' patterns in Graphene, carbon nanotubes of various electrical states and ferro-electrics. In addition to imaging, the technique is suited to a variety of metrology applications where specific physical properties are determined quantitatively. We will present research activities on quantitative measurements using multiple techniques to determine dielectric constant (permittivity) and conductivity (e.g. dopant concentration) for a range of materials. Examples include bulk dielectrics, low-k dielectric thin films, capacitance standards and doped semiconductors. Funded in part by DOE SBIR DE-SC0009586.

  4. Alternating current impedance imaging of high-resistance membrane pores using a scanning electrochemical microscope. Application of membrane electrical shunts to increase measurement sensitivity and image contrast.

    PubMed

    Ervin, Eric Nathan; White, Henry S; Baker, Lane A; Martin, Charles R

    2006-09-15

    Whether an individual pore in a porous membrane can be imaged using scanning electrochemical microscopy (SECM), operated in ac impedance mode, is determined by the magnitude of the change in the total impedance of the imaging system as the SECM tip is scanned over the pore. In instances when the SECM tip resistance is small relative to the internal pore resistance, the total impedance changes by a negligible amount, rendering the pore invisible during impedance imaging. A simple solution to this problem is to introduce a low-impedance electrical shunt (i.e., a salt bridge) across the membrane. This principle is demonstrated by imaging polycarbonate membranes (6-12-microm thickness) containing between 1 and 2000 conical-shaped pores (60-nm- and 2.5-microm-diameter openings) using an approximately 1-microm-radius Pt tip. Theory and experiments show that image contrast (the change in ac current measured as the probe is scanned over the pore) is inversely proportional to the total resistance of the membrane and can be increased by a factor of approximately 50x by introducing a low-resistance electrical shunt across the membrane. Remarkably, SECM images of membranes containing a single high-resistance (approximately 1 G Omega) pore can only be imaged by short-circuiting the membrane. Image contrast also becomes independent of membrane resistance when an electrical shunt is used, allowing for more quantitative comparisons of the features in ac impedance images of different membranes. PMID:16970331

  5. Gynecologic electrical impedance tomograph

    NASA Astrophysics Data System (ADS)

    Korjenevsky, A.; Cherepenin, V.; Trokhanova, O.; Tuykin, T.

    2010-04-01

    Electrical impedance tomography extends to the new and new areas of the medical diagnostics: lungs, breast, prostate, etc. The feedback from the doctors who use our breast EIT diagnostic system has induced us to develop the 3D electrical impedance imaging device for diagnostics of the cervix of the uterus - gynecologic impedance tomograph (GIT). The device uses the same measuring approach as the breast imaging system: 2D flat array of the electrodes arranged on the probe with handle is placed against the body. Each of the 32 electrodes of the array is connected in turn to the current source while the rest electrodes acquire the potentials on the surface. The current flows through the electrode of the array and returns through the remote electrode placed on the patient's limb. The voltages are measured relative to another remote electrode. The 3D backprojection along equipotential surfaces is used to reconstruct conductivity distribution up to approximately 1 cm in depth. Small number of electrodes enables us to implement real time imaging with a few frames per sec. rate. The device is under initial testing and evaluation of the imaging capabilities and suitability of usage.

  6. Advances in imaging and quantification of electrical properties at the nanoscale using Scanning Microwave Impedance Microscopy (sMIM)

    NASA Astrophysics Data System (ADS)

    Friedman, Stuart; Stanke, Fred; Yang, Yongliang; Amster, Oskar

    Scanning Microwave Impedance Microscopy (sMIM) is a mode for Atomic Force Microscopy (AFM) enabling imaging of unique contrast mechanisms and measurement of local permittivity and conductivity at the 10's of nm length scale. sMIM has been applied to a variety of systems including nanotubes, nanowires, 2D materials, photovoltaics and semiconductor devices. Early results were largely semi-quantitative. This talk will focus on techniques for extracting quantitative physical parameters such as permittivity, conductivity, doping concentrations and thin film properties from sMIM data. Particular attention will be paid to non-linear materials where sMIM has been used to acquire nano-scale capacitance-voltage curves. These curves can be used to identify the dopant type (n vs p) and doping level in doped semiconductors, both bulk samples and devices. Supported in part by DOE-SBIR DE-SC0009856.

  7. Impedance feedback control for scanning electrochemical microscopy.

    PubMed

    Alpuche-Aviles, M A; Wipf, D O

    2001-10-15

    A new constant-distance imaging method based on the relationship between tip impedance and tip-substrate separation has been developed for the scanning electrochemical microscope. The tip impedance is monitored by application of a high-frequency ac voltage bias between the tip and auxiliary electrode. The high-frequency ac current is easily separated from the dc-level faradaic electrochemistry with a simple RC filter, which allows impedance measurements during feedback or generation/collection experiments. By employing a piezo-based feedback controller, we are able to maintain the impedance at a constant value and, thus, maintain a constant tip-substrate separation. Application of the method to feedback and generation/collection experiments with tip electrodes as small as 2 microm is presented. PMID:11681463

  8. Electrical impedance of FCC

    NASA Technical Reports Server (NTRS)

    Liu, Y. S.

    1972-01-01

    The electrical characteristics of FCC are investigated in the context of multiple transmission lines theory. Analytical expressions for the coefficients of capacitance of conductors in a single cable are obtained. Numerical values calculated with these expressions are in good agreement with experimental data. Crosstalk, attenuation constants and phase angles of the current and voltage in flat conductor cable are also calculated.

  9. Calibration of electrical impedance tomography

    SciTech Connect

    Daily, W; Ramirez, A

    2000-05-01

    Over the past 10 years we have developed methods for imaging the electrical resistivity of soil and rock formations. These technologies have been called electrical resistance tomography of ERT (e.g. Daily and Owen, 1991). Recently we have been striving to extend this capability to include images of electric impedance--with a new nomenclature of electrical impedance tomography or EIT (Ramirez et al., 1999). Electrical impedance is simply a generalization of resistance. Whereas resistance is the zero frequency ratio of voltage and current, impedance includes both the magnitude and phase relationship between voltage and current at frequency. This phase and its frequency behavior is closely related to what in geophysics is called induced polarization or (Sumner, 1976). Why is this phase or IP important? IP is known to be related to many physical phenomena of importance so that image of IP will be maps of such things as mineralization and cation exchange IP (Marshall and Madden, 1959). Also, it is likely that IP, used in conjunction with resistivity, will yield information about the subsurface that can not be obtained by either piece of information separately. In order to define the accuracy of our technologies to image impedance we have constructed a physical model of known impedance that can be used as a calibration standard. It consists of 616 resistors, along with some capacitors to provide the reactive response, arranged in a three dimensional structure as in figure 1. Figure 2 shows the construction of the network and defines the coordinate system used to describe it. This network of components is a bounded and discrete version of the unbounded and continuous medium with which we normally work (the subsurface). The network has several desirable qualities: (1) The impedance values are known (to the accuracy of the component values). (2) The component values and their 3D distribution is easily controlled. (3) Error associated with electrode noise is eliminated. (4

  10. Electrical Impedance Tomography of Electrolysis

    PubMed Central

    Meir, Arie; Rubinsky, Boris

    2015-01-01

    The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT). The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations. PMID:26039686

  11. Electrical impedance scanning as a new imaging modality in breast cancer detection—a short review of clinical value on breast application, limitations and perspectives

    NASA Astrophysics Data System (ADS)

    Malich, A.; Böhm, T.; Facius, M.; Kleinteich, I.; Fleck, M.; Sauner, D.; Anderson, R.; Kaiser, W. A.

    2003-01-01

    Objective. Cancer cells exhibit altered local dielectric properties compared to normal cells, measurable as different electrical conductance and capacitance using electrical impedance scanning (EIS). Therefore, active biocompatible current is applied to the patient for calculation of both parameters taking into account frequency, voltage and current flow. Subjects and methods. 240 women with 280 sonographically and/or mammographically suspicious findings were examined using EIS. All lesions were histologically proven. A lesion was scored as positive, when a focal increased conductance and/or capacitance was measurable using EIS. The lesion was visible as a bright area in a 256 grey-scale computer output. Due to system limitations patients having a pacemaker or pregnant had to be excluded from the study. Results. 91/113 malignant and 108/167 benign lesions were correctly identified using EIS (80.5% sensitivity, 64.7% specificity). NPV and PPV of 83.1% and 60.7% were observed, respectively. Accuracy was 0.73. A wide range of factors can induce false positive results, although by an experienced observer a number of these findings can be detected such as scars, skin alterations, contact artefacts, air bubbles and naevi, hairs and interfering bone. Based upon visibility on ultrasound (194 lesions visible, 86 not visible) significant differences in the detection rate occurred. Histology-dependent detectability rate varied significantly with lowest rate in CIS-cases (50%). Specificity values varied histology-depending, too; probably depending on the rate of proliferation between 75% (inflammatory lesions) and papillomata (50%). Best detectability was observed in malignant lesions with a size between 20 and 30 mm. Further possible applications will be discussed regarding the currently available literature (lymph nodes, salivary glands, mathematical and animal based models). Conclusion. EIS appears to be a promising new additional technology providing a rather high

  12. Possibilities of electrical impedance tomography in gynecology

    NASA Astrophysics Data System (ADS)

    V, Trokhanova O.; A, Chijova Y.; B, Okhapkin M.; V, Korjenevsky A.; S, Tuykin T.

    2013-04-01

    The paper describes results of comprehensive EIT diagnostics of mammary glands and cervix. The data were obtained from examinations of 170 patients by EIT system MEM (multi-frequency electrical impedance mammograph) and EIT system GIT (gynecological impedance tomograph). Mutual dependence is discussed.

  13. Measurements of electrical impedance of biomedical objects.

    PubMed

    Frączek, Marcin; Kręcicki, Tomasz; Moron, Zbigniew; Krzywaźnia, Adam; Ociepka, Janusz; Rucki, Zbigniew; Szczepanik, Zdzisław

    2016-01-01

    Some basic problems related to measurements of electrical impedance of biological objects (bioimpedance) have been presented in this paper. Particularly problems arising from impedance occurring at the sensor-tissue interface (interfacial impedances) in contact measuring methods have been discussed. The influence of finite values of impedances of the current source and voltage measuring device has also been taken into consideration. A model of the impedance sensor for the four-electrode measurement method containing the interfacial, source and measuring device impedances has been given and its frequency characteristics obtained by the computer simulation have been presented. The influence of these impedances on the shape of frequency characteristic of the sensor model has been discussed. Measurements of bioimpedance of healthy and anomalous soft tissues have been described. Some experimental results, particularly the frequency characteristics of bioimpedance, have been shown. The presented results of measurement show that bioimpedance can be a valuable source of information about the tissues, so measurement of bioimpedance can be a useful supplement to other medical diagnostic methods. PMID:27151250

  14. Arts of electrical impedance tomographic sensing

    PubMed Central

    Wang, Mi; Wang, Qiang; Karki, Bishal

    2016-01-01

    This paper reviews governing theorems in electrical impedance sensing for analysing the relationships of boundary voltages obtained from different sensing strategies. It reports that both the boundary voltage values and the associated sensitivity matrix of an alternative sensing strategy can be derived from a set of full independent measurements and sensitivity matrix obtained from other sensing strategy. A new sensing method for regional imaging with limited measurements is reported. It also proves that the sensitivity coefficient back-projection algorithm does not always work for all sensing strategies, unless the diagonal elements of the transformed matrix, ATA, have significant values and can be approximate to a diagonal matrix. Imaging capabilities of few sensing strategies were verified with static set-ups, which suggest the adjacent electrode pair sensing strategy displays better performance compared with the diametrically opposite protocol, with both the back-projection and multi-step image reconstruction methods. An application of electrical impedance tomography for sensing gas in water two-phase flows is demonstrated. This article is part of the themed issue ‘Supersensing through industrial process tomography’. PMID:27185968

  15. Arts of electrical impedance tomographic sensing.

    PubMed

    Wang, Mi; Wang, Qiang; Karki, Bishal

    2016-06-28

    This paper reviews governing theorems in electrical impedance sensing for analysing the relationships of boundary voltages obtained from different sensing strategies. It reports that both the boundary voltage values and the associated sensitivity matrix of an alternative sensing strategy can be derived from a set of full independent measurements and sensitivity matrix obtained from other sensing strategy. A new sensing method for regional imaging with limited measurements is reported. It also proves that the sensitivity coefficient back-projection algorithm does not always work for all sensing strategies, unless the diagonal elements of the transformed matrix, A(T)A, have significant values and can be approximate to a diagonal matrix. Imaging capabilities of few sensing strategies were verified with static set-ups, which suggest the adjacent electrode pair sensing strategy displays better performance compared with the diametrically opposite protocol, with both the back-projection and multi-step image reconstruction methods. An application of electrical impedance tomography for sensing gas in water two-phase flows is demonstrated. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185968

  16. Electrical impedance tomography: so close to touching the holy grail

    PubMed Central

    2014-01-01

    Electrical impedance tomography is a new technology giving us lung imaging that may allow lung function to be monitored at the bedside. Several applications have been studied to guide mechanical ventilation at the bedside with electrical impedance tomography. Positive end-expiratory pressure trials guided by electrical impedance tomography are relevant in terms of recruited volume or homogeneity of the lung. Tidal impedance variation is a new parameter of electrical impedance tomography that may help physicians with ventilator settings in acute respiratory distress syndrome patients. This parameter is able to identify the onset of overdistention in the nondependent part and recruitment in the dependent part. Electrical impedance tomography presents a big step forward in mechanical ventilation. PMID:25041593

  17. Infrared Scanning For Electrical Maintenance

    NASA Astrophysics Data System (ADS)

    Eisenbath, Steven E.

    1983-03-01

    Given the technological age that we have now entered, the purpose of this paper is to relate how infrared scanning can be used for an electrical preventative maintenance program. An infrared scanner is able to produce an image because objects give off infrared radiation in relationship to their temperature. Most electrical problems will show up as an increase in temperature, thereby making the infrared scanner a useful preventative maintenance tool. Because of the sensitivity of most of the scanners, .1 to .2 of a degree, virtually all electrical problems can be pinpointed long before they become a costly failure. One of the early uses of infrared scanning was to check the power company's electrical distribution system. Most of this was performed via aircraft or truck mounted scanning devices which necessitated its semi-permanent mounting. With the advent of small hand held infrared imagers, along with more portability of the larger systems, infrared scanning has gained more popularity in checking electrical distribution systems. But the distribution systems are now a scaled down model, mainly the in-plant electrical systems. By in-plant, I mean any distribution of electricity; once it leaves the power company's grid. This can be in a hospital, retail outlet, warehouse or manufacturing facility.

  18. Modified sparse regularization for electrical impedance tomography.

    PubMed

    Fan, Wenru; Wang, Huaxiang; Xue, Qian; Cui, Ziqiang; Sun, Benyuan; Wang, Qi

    2016-03-01

    Electrical impedance tomography (EIT) aims to estimate the electrical properties at the interior of an object from current-voltage measurements on its boundary. It has been widely investigated due to its advantages of low cost, non-radiation, non-invasiveness, and high speed. Image reconstruction of EIT is a nonlinear and ill-posed inverse problem. Therefore, regularization techniques like Tikhonov regularization are used to solve the inverse problem. A sparse regularization based on L1 norm exhibits superiority in preserving boundary information at sharp changes or discontinuous areas in the image. However, the limitation of sparse regularization lies in the time consumption for solving the problem. In order to further improve the calculation speed of sparse regularization, a modified method based on separable approximation algorithm is proposed by using adaptive step-size and preconditioning technique. Both simulation and experimental results show the effectiveness of the proposed method in improving the image quality and real-time performance in the presence of different noise intensities and conductivity contrasts. PMID:27036798

  19. Protein Aggregation Measurement through Electrical Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Affanni, A.; Corazza, A.; Esposito, G.; Fogolari, F.; Polano, M.

    2013-09-01

    The paper presents a novel methodology to measure the fibril formation in protein solutions. We designed a bench consisting of a sensor having interdigitated electrodes, a PDMS hermetic reservoir and an impedance meter automatically driven by calculator. The impedance data are interpolated with a lumped elements model and their change over time can provide information on the aggregation process. Encouraging results have been obtained by testing the methodology on K-casein, a protein of milk, with and without the addition of a drug inhibiting the aggregation. The amount of sample needed to perform this measurement is by far lower than the amount needed by fluorescence analysis.

  20. Diagnostic criteria for mass lesions differentiating in electrical impedance mammography

    NASA Astrophysics Data System (ADS)

    A, Karpov; M, Korotkova

    2013-04-01

    The purpose of this research was to determine the diagnostic criteria for differentiating volumetric lesions in the mammary gland in electrical impedance mammography. The research was carried out utilizing the electrical impedance computer mammograph llMEIK v.5.6gg®, which enables to acquire images of 3-D conductivity distribution layers within mamma's tissues up to 5 cm depth. The weighted reciprocal projection method was employed to reconstruct the 3-D electric conductivity distribution of the examined organ. The results of 3,710 electrical impedance examinations were analyzed. The analysis of a volumetric lesion included assessment of its shape, contour, internal electrical structure and changes of the surrounding tissues. Moreover, mammary gland status was evaluated with the help of comparative and age-related electrical conductivity curves. The diagnostic chart is provided. Each criterion is measured in points. Using the numerical score for evaluation of mass and non-volumetric lesions within the mammary gland in electrical impedance mammography allowed comparing this information to BI-RADS categories developed by American College of Radiology experts. The article is illustrated with electrical impedance mammograms and tables.

  1. Electrical Impedance Tomography Technology (EITT) Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J.

    2014-01-01

    Development of a portable, lightweight device providing two-dimensional tomographic imaging of the human body using impedance mapping. This technology can be developed to evaluate health risks and provide appropriate medical care on the ISS, during space travel and on the ground.

  2. Motion discrimination of throwing a baseball using forearm electrical impedance

    NASA Astrophysics Data System (ADS)

    Nakamura, Takao; Kusuhara, Toshimasa; Yamamoto, Yoshitake

    2013-04-01

    The extroversion or hyperextension of elbow joint cause disorders of elbow joint in throwing a baseball. A method, which is easy handling and to measure motion objectively, can be useful for evaluation of throwing motion. We investigated a possibility of motion discrimination of throwing a baseball using electrical impedance method. The parameters of frequency characteristics (Cole-Cole arc) of forearm electrical impedance were measured during four types of throwing a baseball. Multiple discriminant analysis was used and the independent variables were change ratios of 11 parameters of forearm electrical impedance. As results of 120 data with four types of throwing motion in three subjects, hitting ratio was very high and 95.8%. We can expect to discriminate throwing a baseball using multiple discriminant analysis of impedance parameters.

  3. Electric impedance imaging of the mammary gland in the case of mastitis

    NASA Astrophysics Data System (ADS)

    Korotkova, M.; Karpov, A.

    2010-04-01

    The electric impedance mammography technique has been applied for several years. The aim of the research in hand is to reveal the peculiarities of the electric impedance imaging in various stages of the inflammatory process in the mammary gland. We have conducted an examination of twenty six patients: five of them in the stage of arterial hyperemia, eight in the stage of infiltration, three of them in the stage of abscess and ten in the stage of cicatrization. The examination was carried out on the "MEIK" (version 5.6) potencial electric impedance computer mammograph. The weighted reciprocal projection method was used to reconstruct the 3-D electric conductivity distribution of the examined organ. Any inflammatory process is phasic and always attended by the complex vascular alterations with exudation of liquid components of plasma, blood cells outwandering and stromal cells proliferation. Pathophysiological and histopathological peculiarities of each stage of the inflammatory process are well reflected in the electric impedance images. This fact enabled the authors of the research to define the electric impedance imaging as the histofunctional scanning.

  4. Statistical Properties of Antenna Impedance in an Electrically Large Cavity

    SciTech Connect

    WARNE,LARRY K.; LEE,KELVIN S.H.; HUDSON,H. GERALD; JOHNSON,WILLIAM A.; JORGENSON,ROY E.; STRONACH,STEPHEN L.

    2000-12-13

    This paper presents models and measurements of antenna input impedance in resonant cavities at high frequencies.The behavior of input impedance is useful in determining the transmission and reception characteristics of an antenna (as well as the transmission characteristics of certain apertures). Results are presented for both the case where the cavity is undermoded (modes with separate and discrete spectra) as well as the over moded case (modes with overlapping spectra). A modal series is constructed and analyzed to determine the impedance statistical distribution. Both electrically small as well as electrically longer resonant and wall mounted antennas are analyzed. Measurements in a large mode stirred chamber cavity are compared with calculations. Finally a method based on power arguments is given, yielding simple formulas for the impedance distribution.

  5. Impedance analysis of fibroblastic cell layers measured by electric cell-substrate impedance sensing

    NASA Astrophysics Data System (ADS)

    Lo, Chun-Min; Ferrier, Jack

    1998-06-01

    Impedance measurements of cell layers cultured on gold electrode surfaces obtained by electric cell-substrate impedance sensing provide morphological information such as junctional resistance and cell-substrate separation. Previously, a model that assumes that cells have a disklike shape and that electric currents flow radially underneath the ventral cell surface and then through the paracellular space has been used to theoretically calculate the impedance of the cell-covered electrode. In this paper we propose an extended model of impedance analysis for cell layers where cellular shape is rectangular. This is especially appropriate for normal fibroblasts in culture. To verify the model, we analyze impedance data obtained from four different kinds of fibroblasts that display a long rectangular shape. In addition, we measure the average cell-substrate separation of human gingival fibroblasts at different temperatures. At temperatures of 37, 22, and 4 °C, the average separation between ventral cell surface and substratum are 46, 55, and 89 nm, respectively.

  6. Microbial Sulfate Reduction Measured by an Automated Electrical Impedance Technique

    NASA Technical Reports Server (NTRS)

    Oremland, R. S.; Silverman, M. P.

    1979-01-01

    Electrical impedance measurements are used to investigate the rates of sulfate reduction by pure cultures of and sediments containing sulfur-reducing bacteria. Changes in the electrical impedance ratios of pure cultures of Desulfovibrio aestuarii and samples of reduced sediments from San Francisco Bay were measured by a Bactometer 32, and sulfate reduction was followed by measuring the incorporation of (S-35) sulfate into metal sulfides. The growth of the bacteria in pure culture is found to result in an increase of 0.2200 in the impedance ratio within 24 h, accompanied by increases in protein, ATP, sulfide and absorptance at 660 nm, all of which are inhibited by the addition of molybdate. Similar responses were observed in the sediments, although impedance ratio responses were not completely inhibited upon the addition of molybdate, due to the presence of nonsulfate-respiring microorganisms. Experiments conducted with sterile media and autoclaved sediments indicate that the presence of H2S together with iron is responsible for the impedance effect, and sulfate reduction rates ranging between 0.85 and 1.78 mmol/l per day are estimated for the sediments by the impedance technique.

  7. The development of algorithms in electrical impedance computerized tomography.

    PubMed

    Shie, J R; Li, C J; Lin, J T

    2000-01-01

    Electrical Impedance Computerized Tomography (EICT) is an imaging method to reconstruct the impedance distribution inside of domain through the boundary injected current and display the impedance contrast ratio as an image. This paper concentrates on developing two algorithms to enhance the quality of the conductivity image. The two algorithms are "Fine-Mesh Conversion Method" and "Sub-Domain EICT Method". "Fine-Mesh Conversion Method" is a numerical calibration process to find a coarse mesh impedance network that behaves like a fine mesh network in terms of giving similar voltages under the same current excitations. "Sub-Domain EICT" solves a higher resolution EICT with the cost of a lower resolution EICT by combining "Fine-Mesh Conversion Method", and a Fuzzy Logic Inference Systems (FLIS) classifier. PMID:10834231

  8. Electrical impedance imaging of water distribution in the root zone

    NASA Astrophysics Data System (ADS)

    Newill, P.; Karadaglić, D.; Podd, F.; Grieve, B. D.; York, T. A.

    2014-05-01

    The paper describes a technique that is proposed for imaging water transport in and around the root zone of plants using distributed measurements of electrical impedance. The technique has the potential to analyse sub-surface phenotypes, for instance drought tolerance traits in crop breeding programmes. The technical aim is to implement an automated, low cost, instrument for high-throughput screening. Ultimately the technique is targeted at in-field, on-line, measurements. For demonstration purposes the present work considers measurements on laboratory scale rhizotrons housing growing maize plants. Each rhizotron is fitted with 60 electrodes in a rectangular array. To reduce electrochemical effects the capacitively coupled contactless conductivity (C4D) electrodes have an insulating layer on the surface and the resistance of the bulk material is deduced from spectroscopic considerations. Electrical impedance is measured between pairs of electrodes to build up a two-dimensional map. A modified electrical model of such electrodes is proposed which includes the resistive and reactive components of both the insulating layer and the bulk material. Measurements taken on a parallel-plate test cell containing water confirm that the C4D technique is able to measure electrical impedance. The test cell has been used to explore the effects of water content, compaction and temperature on measurements in soil. Results confirm that electrical impedance measurements are very sensitive to moisture content. Impedance fraction changes up to 20% are observed due to compaction up to a pressure of 0.21 kg cm-2 and a temperature fraction sensitivity of about 2%/°C. The effects of compaction and temperature are most significant under dry conditions. Measurements on growing maize reveal the changes in impedance across the rhizotron over a period of several weeks. Results are compared to a control vessel housing only soil.

  9. Electrical impedance tomography of the 1995 OGI gasoline release

    SciTech Connect

    Daily, W.; Ramirez, A.

    1996-10-01

    Electrical impedance tomography (EIT) was used to image the plume resulting from a release of 378 liters (100 gallons) of gasoline into a sandy acquifer. Images were made in 5 planes before and 5 times during the release, to generate a detailed picture of the spatial as well as the temporal development of the plume as it spread at the water table. Information of the electrical impedance (both in phase and out of phase voltages) was used or several different frequencies to produce images. We observed little dispersion in the images either before or after the gasoline entered the acquifer. Likewise, despite some laboratory measurements of impedances, there was no evidence of a change in the reactance in the soil because of the gasoline.

  10. Electrical-Impedance-Based Ice-Thickness Gauges

    NASA Technical Reports Server (NTRS)

    Weinstein, Leonard

    2003-01-01

    Langley Research Center has developed electrical-impedance-based ice-thickness gauges and is seeking partners and collaborators to commercialize them. When used as parts of active monitoring and diagnostic systems, these gauges make it possible to begin deicing or to take other protective measures before ice accretes to dangerous levels. These gauges are inexpensive, small, and simple to produce. They can be adapted to use on a variety of stationary and moving structures that are subject to accumulation of ice. Examples of such structures include aircraft, cars, trucks, ships, buildings, towers, power lines (see figure), power-generating equipment, water pipes, freezer compartments, and cooling coils. A gauge of this type includes a temperature sensor and two or more pairs of electrically insulated conductors embedded in a surface on which ice could accumulate. The electrical impedances of the pairs of conductors vary with the thickness of any ice that may be present. Somewhat more specifically, when the pairs of conductors are spaced appropriately, the ratio between their impedances is indicative of the thickness of the ice. Therefore, the gauge includes embedded electronic circuits that measure the electrical impedances, plus circuits that process the combination of temperature and impedance measurements to determine whether ice is present and, if so, how thick it is. Of course, in the processing of the impedance measurements, the temperature measurements help the circuitry to distinguish between liquid water and ice. The basic design of a gauge of this type can be adapted to local conditions. For example, if there is a need to monitor ice over a wide range of thickness, then the gauge can include more than two sets of conductors having various spacings.

  11. Cervical cancer detection by electrical impedance in a Colombian setting

    NASA Astrophysics Data System (ADS)

    Miranda, David A.; Corzo, Sandra P.; González Correa, C. A.

    2013-04-01

    Electrical properties of normal and neoplastic cervical tissues in a heterogeneous group of 56 Colombian women were studied by electrical impedance spectroscopy and a model based on the Generalized Effective-Medium Theory of Induced Polarization (GEMTIP). Differences between the electrical bioimpedance spectra were correlated with cellular and tissue parameters. The analysis performed by the proposed model suggest that the number of different types of cellular layers that form the biological tissue, the intracellular and extracellular conductivity could be used to explain the differences between electrical bioimpedance spectra in normal and neoplastic tissues.

  12. Clinical implementation of electrical impedance tomography with hyperthermia.

    PubMed

    Moskowitz, M J; Ryan, T P; Paulsen, K D; Mitchell, S E

    1995-01-01

    We describe the use of electrical impedance tomography (EIT) for non-invasive thermal imaging in conjunction with a clinical treatment of a superficial scalp lesion utilizing a spiral microstrip antenna. This is our first reported use of EIT with a clinical hyperthermia treatment and perhaps the first world-wide. The thermal measurements recorded during treatment compare favourably with the images reconstructed from impedance data gathered during heating. A linear relation, measured in phantom material, between the change in temperature with the change in reconstructed impedance was assumed. The average discrepancy between the measured temperature changes with the temperatures reconstructed from the impedance changes was 1.4 degrees C, with the maximum being 8.9 degrees C. These preliminary data suggest that impedance changes can be measured during hyperthermia delivery and temperature estimates based on these observed changes are possible in the clinical setting. These findings also point to the complex, yet critical nature of the impedance versus temperature relationship for tissue in vivo. The reconstructed thermal images may provide complementary information about the overall thermal damage imposed during heating. Based on this initial clinical experience we feel that EIT has great potential as a viable clinical aid in imaging the temperature changes imposed during hyperthermia. PMID:7790730

  13. Damage Diagnosis in Semiconductive Materials Using Electrical Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Ross, Richard W.; Hinton, Yolanda L.

    2008-01-01

    Recent aerospace industry trends have resulted in an increased demand for real-time, effective techniques for in-flight structural health monitoring. A promising technique for damage diagnosis uses electrical impedance measurements of semiconductive materials. By applying a small electrical current into a material specimen and measuring the corresponding voltages at various locations on the specimen, changes in the electrical characteristics due to the presence of damage can be assessed. An artificial neural network uses these changes in electrical properties to provide an inverse solution that estimates the location and magnitude of the damage. The advantage of the electrical impedance method over other damage diagnosis techniques is that it uses the material as the sensor. Simple voltage measurements can be used instead of discrete sensors, resulting in a reduction in weight and system complexity. This research effort extends previous work by employing finite element method models to improve accuracy of complex models with anisotropic conductivities and by enhancing the computational efficiency of the inverse techniques. The paper demonstrates a proof of concept of a damage diagnosis approach using electrical impedance methods and a neural network as an effective tool for in-flight diagnosis of structural damage to aircraft components.

  14. A mathematical model for electrical impedance spectroscopy of zwitterionic hydrogels.

    PubMed

    Feicht, Sarah E; Khair, Aditya S

    2016-08-17

    We report a mathematical model for ion transport and electrical impedance in zwitterionic hydrogels, which possess acidic and basic functional groups that carry a net charge at a pH not equal to the isoelectric point. Such hydrogels can act as an electro-mechanical interface between a relatively hard biosensor and soft tissue in the body. For this application, the electrical impedance of the hydrogel must be characterized to ensure that ion transport to the biosensor is not significantly hindered. The electrical impedance is the ratio of the applied voltage to the measured current. We consider a simple model system, wherein an oscillating voltage is applied across a hydrogel immersed in electrolyte and sandwiched between parallel, blocking electrodes. We employ the Poisson-Nernst-Planck (PNP) equations coupled with acid-base dissociation reactions for the charge on the hydrogel backbone to model the ionic transport across the hydrogel. The electrical impedance is calculated from the numerical solution to the PNP equations and subsequently analyzed via an equivalent circuit model to extract the hydrogel capacitance, resistance, and the capacitance of electrical double layers at the electrode-hydrogel interface. For example, we predict that an increase in pH from the isoelectric point, pH = 6.4 for a model PCBMA hydrogel, to pH = 8 reduces the resistance of the hydrogel by ∼40% and increases the double layer capacitance by ∼250% at an electrolyte concentration of 0.1 mM. The significant impact of charged hydrogel functional groups to the impedance is damped at higher electrolyte concentration. PMID:27464763

  15. Electrical Impedance of Ionic Polymeric Metal Composites

    NASA Technical Reports Server (NTRS)

    Leary, S.; Bar-Cohen, Y.

    1999-01-01

    In recent years the use of ionic polymer metal composites such as Nafion-based platinum ionomers have emerged as electroactive polymer materials with great potential for robotics and other applications. An effective activation of these materials requires understanding of their mechanism of operation. Generally, the material needs to be maintained hydrated to assure its electromechanical activity. To allow the control of the response of the material, a study is underway to investigate the electrical response. Particular emphasis is placed on possible electrochemical reactions and deviations from linear dielectric behavior. Currently, efforts are made to determine the necessary drive characteristics of the source to allow low power operation (< or = 1.0 W) of the material as an actuator.

  16. Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy

    2015-05-01

    Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.

  17. Bladder Cancer Detection Using Electrical Impedance Technique (Tabriz Mark 1)

    PubMed Central

    Keshtkar, Ahmad; Salehnia, Zeinab; Keshtkar, Asghar; Shokouhi, Behrooz

    2012-01-01

    Bladder cancer is the fourth most common malignant neoplasm in men and the eighth in women. Bladder pathology is usually investigated visually by cystoscopy. In this technique, biopsies are obtained from the suspected area and then, after needed procedure, the diagnostic information can be taken. This is a relatively difficult procedure and is associated with discomfort for the patient and morbidity. Therefore, the electrical impedance spectroscopy (EIS), a minimally invasive screening technique, can be used to separate malignant areas from nonmalignant areas in the urinary bladder. The feasibility of adapting this technique to screen for bladder cancer and abnormalities during cystoscopy has been explored and compared with histopathological evaluation of urinary bladder lesions. Ex vivo studies were carried out in this study by using a total of 30 measured points from malignant and 100 measured points from non-malignant areas of patients bladders in terms of their biopsy reports matching to the electrical impedance measurements. In all measurements, the impedivity of malignant area of bladder tissue was significantly higher than the impedivity of non-malignant area this tissue (P < 0.005). PMID:22567538

  18. PREFACE: XV International Conference on Electrical Bio-Impedance (ICEBI) & XIV Conference on Electrical Impedance Tomography (EIT)

    NASA Astrophysics Data System (ADS)

    Pliquett, Uwe

    2013-04-01

    Over recent years advanced measurement methods have facilitated outstanding achievements not only in medical instrumentation but also in biotechnology. Impedance measurement is a simple and innocuous way to characterize materials. For more than 40 years biological materials, most of them based on cells, have been characterized by means of electrical impedance for quality control of agricultural products, monitoring of biotechnological or food processes or in health care. Although the list of possible applications is long, very few applications successfully entered the market before the turn of the century. This was, on the one hand, due to the low specificity of electrical impedance with respect to other material properties because it is influenced by multiple factors. On the other hand, equipment and methods for many potential applications were not available. With the appearance of microcontrollers that could be easily integrated in applications at the beginning of the 1980s, impedance measurement advanced as a valuable tool in process optimization and lab automation. However, established methods and data processing were mostly used in a new environment. This has changed significantly during the last 10 years with a dramatic growth of the market for medical instrumentation and also for biotechnological applications. Today, advanced process monitoring and control require fast and highly parallel electrical characterization which in turn yields incredible data volumes that must be handled in real time. Many newer developments require miniaturized but precise sensing methods which is one of the main parts of Lab-on-Chip technology. Moreover, biosensors increasingly use impedometric transducers, which are not compatible with the large expensive measurement devices that are common in the laboratory environment. Following the achievements in the field of bioimpedance measurement, we will now witness a dramatic development of new electrode structures and electronics

  19. PREFACE: XV International Conference on Electrical Bio-Impedance (ICEBI) & XIV Conference on Electrical Impedance Tomography (EIT)

    NASA Astrophysics Data System (ADS)

    Pliquett, Uwe

    2013-04-01

    Over recent years advanced measurement methods have facilitated outstanding achievements not only in medical instrumentation but also in biotechnology. Impedance measurement is a simple and innocuous way to characterize materials. For more than 40 years biological materials, most of them based on cells, have been characterized by means of electrical impedance for quality control of agricultural products, monitoring of biotechnological or food processes or in health care. Although the list of possible applications is long, very few applications successfully entered the market before the turn of the century. This was, on the one hand, due to the low specificity of electrical impedance with respect to other material properties because it is influenced by multiple factors. On the other hand, equipment and methods for many potential applications were not available. With the appearance of microcontrollers that could be easily integrated in applications at the beginning of the 1980s, impedance measurement advanced as a valuable tool in process optimization and lab automation. However, established methods and data processing were mostly used in a new environment. This has changed significantly during the last 10 years with a dramatic growth of the market for medical instrumentation and also for biotechnological applications. Today, advanced process monitoring and control require fast and highly parallel electrical characterization which in turn yields incredible data volumes that must be handled in real time. Many newer developments require miniaturized but precise sensing methods which is one of the main parts of Lab-on-Chip technology. Moreover, biosensors increasingly use impedometric transducers, which are not compatible with the large expensive measurement devices that are common in the laboratory environment. Following the achievements in the field of bioimpedance measurement, we will now witness a dramatic development of new electrode structures and electronics

  20. Local impedance measurement of an electrode/single-pentacene-grain interface by frequency-modulation scanning impedance microscopy

    NASA Astrophysics Data System (ADS)

    Kimura, Tomoharu; Kobayashi, Kei; Yamada, Hirofumi

    2015-08-01

    The device performances of organic thin film transistors are often limited by the metal-organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance of a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.

  1. Local impedance measurement of an electrode/single-pentacene-grain interface by frequency-modulation scanning impedance microscopy

    SciTech Connect

    Kimura, Tomoharu; Yamada, Hirofumi; Kobayashi, Kei

    2015-08-07

    The device performances of organic thin film transistors are often limited by the metal–organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance of a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.

  2. Some Nonlinear Reconstruction Algorithms for Electrical Impedance Tomography

    SciTech Connect

    Berryman, J G

    2001-03-09

    An impedance camera [Henderson and Webster, 1978; Dines and Lytle, 1981]--or what is now more commonly called electrical impedance tomography--attempts to image the electrical impedance (or just the conductivity) distribution inside a body using electrical measurements on its boundary. The method has been used successfully in both biomedical [Brown, 1983; Barber and Brown, 1986; J. C. Newell, D. G. Gisser, and D. Isaacson, 1988; Webster, 1990] and geophysical applications [Wexler, Fry, and Neurnan, 1985; Daily, Lin, and Buscheck, 1987], but the analysis of optimal reconstruction algorithms is still progressing [Murai and Kagawa, 1985; Wexler, Fry, and Neurnan, 1985; Kohn and Vogelius, 1987; Yorkey and Webster, 1987; Yorkey, Webster, and Tompkins, 1987; Berryman and Kohn, 1990; Kohn and McKenney, 1990; Santosa and Vogelius, 1990; Yorkey, 1990]. The most common application is monitoring the influx or efflux of a highly conducting fluid (such as brine in a porous rock or blood in the human body) through the volume being imaged. For biomedical applications, this met hod does not have the resolution of radiological methods, but it is comparatively safe and inexpensive and therefore provides a valuable alternative when continuous monitoring of a patient or process is desired. The following discussion is intended first t o summarize the physics of electrical impedance tomography, then to provide a few details of the data analysis and forward modeling requirements, and finally to outline some of the reconstruction algorithms that have proven to be most useful in practice. Pointers to the literature are provided throughout this brief narrative and the reader is encouraged to explore the references for more complete discussions of the various issues raised here.

  3. Single cell electric impedance topography: mapping membrane capacitance.

    PubMed

    Dharia, Sameera; Ayliffe, Harold E; Rabbitt, Richard D

    2009-12-01

    Single-cell electric impedance topography (sceTopo), a technique introduced here, maps the spatial distribution of capacitance (i.e. displacement current) associated with the membranes of isolated, living cells. Cells were positioned in the center of a circular recording chamber surrounded by eight electrodes. Electrodes were evenly distributed on the periphery of the recording chamber. Electric impedance measured between adjacent electrode pairs (10 kHz-5 MHz) was used to construct topographical maps of the spatial distribution of membrane capacitance. Xenopus Oocytes were used as a model cell to develop sceTopo because these cells consist of two visually distinguishable hemispheres, each with distinct membrane composition and structure. Results showed significant differences in the imaginary component of the impedance between the two oocyte hemispheres. In addition, the same circumferential array was used to map the size of the extracellular electrical shunt path around the cell, providing a means to estimate the location and shape of the cell in the recording chamber. PMID:19904403

  4. Preliminary Results on Different Impedance Contrast Agents for Pulmonary Perfusion Imaging with Electrical Impedance Tomography

    NASA Astrophysics Data System (ADS)

    Nguyen, D. T.; Kosobrodov, R.; Barry, M. A.; Chik, W.; Pouliopoulos, J.; Oh, T. I.; Thiagalingam, A.; McEwan, A.

    2013-04-01

    Recent studies in animal models suggest that the use of small volume boluses of NaCl as an impedance contrast agent can significantly improve pulmonary perfusion imaging by Electrical Impedance Tomography (EIT). However, these studies used highly concentrated NaCl solution (20%) which may have adverse effects on the patients. In a pilot experiment, we address this problem by comparing a number of different Impedance Contrast Boluses (ICBs). Conductivity changes in the lungs of a sheep after the injection of four different ICBs were compared, including three NaCl-based ICBs and one glucose-based ICB. The following procedure was followed for each ICB. Firstly, ventilation was turned off to provide an apneic window of approximately 40s to image the conductivity changes due to the ICB. Each ICB was then injected through a pig-tail catheter directly into the right atrium. EIT images were acquired throughout the apnea to capture the conductivity change. For each ICB, the experiment was repeated three times. The three NaCl-based ICB exhibited similar behaviour in which following the injection of each of these ICBs, the conductivity of each lung predictably increased. The effect of the ICB of 5% glucose solution was inconclusive. A small decrease in conductivity in the left lung was observed in two out of three cases and none was discernible in the right lung.

  5. Electrical impedance tomography with an optimized calculable square sensor.

    PubMed

    Cao, Zhang; Wang, Huaxiang; Xu, Lijun

    2008-10-01

    Electrical impedance tomography is a technique that reconstructs the medium distribution in a region of interest through electrical measurements on its boundary. In this paper, an optimized square sensor was designed for electrical impedance tomography in order to obtain maximum information over the cross section of interest, e.g., circulating fluidized beds, in the sense of Shannon information entropy. An analytical model of the sensor was obtained using the conformal transformation. The model indicates that the square sensor possesses calculable property, which allows the calculation of standard values of the sensor directly from a single dimensional measurement that can be made traceable to the SI unit of length. Based on the model, the sensitivity maps and electrical field lines can be calculated in less than a second. Two model based algorithms for image reconstruction, i.e., back projection algorithm based on electrical field lines and iterative Lavrentiev regularization algorithm based on the sensitivity map, were introduced. Simulated results and experimental results validate the feasibility of the algorithms. PMID:19044722

  6. In Situ Characterization of Ultrathin Films by Scanning Electrochemical Impedance Microscopy.

    PubMed

    Estrada-Vargas, Arturo; Bandarenka, Aliaksandr; Kuznetsov, Volodymyr; Schuhmann, Wolfgang

    2016-03-15

    Control over the properties of ultrathin films plays a crucial role in many fields of science and technology. Although nondestructive optical and electrical methods have multiple advantages for local surface characterization, their applicability is very limited if the surface is in contact with an electrolyte solution. Local electrochemical methods, e.g., scanning electrochemical microscopy (SECM), cannot be used as a robust alternative yet because their methodological aspects are not sufficiently developed with respect to these systems. The recently proposed scanning electrochemical impedance microscopy (SEIM) can efficiently elucidate many key properties of the solid/liquid interface such as charge transfer resistance or interfacial capacitance. However, many fundamental aspects related to SEIM application still remain unclear. In this work, a methodology for the interpretation of SEIM data of "charge blocking systems" has been elaborated with the help of finite element simulations in combination with experimental results. As a proof of concept, the local film thickness has been visualized using model systems at various tip-to-sample separations. Namely, anodized aluminum oxide (Al2O3, 2-20 nm) and self-assembled monolayers based on 11-mercapto-1-undecanol and 16-mercapto-1-hexadecanethiol (2.1 and 2.9 nm, respectively) were used as model systems. PMID:26871004

  7. Embedded silver PDMS electrodes for single cell electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Wei, Yuan; Xu, Zhensong; Cachia, Mark A.; Nguyen, John; Zheng, Yi; Wang, Chen; Sun, Yu

    2016-09-01

    This paper presents a microfluidic device with wide channels and embedded AgPDMS electrodes for measuring the electrical properties of single cells. The work demonstrates the feasibility of using a large channel design and embedded electrodes for impedance spectroscopy to circumvent issues such as channel clogging and limited device re-usability. AgPDMS electrodes were formed on channel sidewalls for impedance detection and cell electrical properties measurement. Equivalent circuit models were used to interpret multi-frequency impedance data to quantify each cell’s cytoplasm conductivity and specific membrane capacitance. T24 cells were tested to validate the microfluidic system and modeling results. Comparisons were then made by measuring two leukemia cell lines (AML-2 and HL-60) which were found to have different cytoplasm conductivity values (0.29  ±  0.15 S m‑1 versus 0.47  ±  0.20 S m‑1) and specific membrane capacitance values (41  ±  25 mF m‑2 versus 55  ±  26 mF m‑2) when the cells were flown through the wide channel and measured by the AgPDMS electrodes.

  8. Optimal multisine excitation design for broadband electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Sanchez, B.; Vandersteen, G.; Bragos, R.; Schoukens, J.

    2011-11-01

    Electrical impedance spectroscopy (EIS) can be used to characterize biological materials in applications ranging from cell culture to body composition, including tissue and organ state. The emergence of cell therapy and tissue engineering opens up a new and promising field of application. While in most cases classical measurement techniques based on a frequency sweep can be used, EIS based on broadband excitations enables dynamic biological systems to be characterized when the measuring time and injected energy are a constraint. Myocardial regeneration, cell characterization in micro-fluidic systems and dynamic electrical impedance tomography are all examples of such applications. The weakness of such types of fast EIS measuring techniques resides in their intrinsic loss of accuracy. However, since most of the practical applications have no restriction over the excitation used, the input power spectrum can be appropriately designed to maximize the accuracy obtained from the measurements. This paper deals with the problem of designing the optimal multisine excitation for electrical bioimpedance measurements. The optimal multisine is obtained by the minimization of the Cramer-Rao lower bound, or what is the same, by maximizing the accuracy obtained from the measurements. Furthermore, because no analytical solution exists for global optimization involving time and frequency domains jointly, this paper presents the multisine optimization approach partially in both domains and then combines the results. As regards the frequency domain approach, a novel contribution is made for the multisine amplitude power spectrum. In the time domain, multisine is optimized by reducing its crest factor. Moreover, the impact on the information and accuracy of the impedance spectrum obtained from using different multisine amplitude power spectra is discussed, as well as the number of frequencies and frequency distributions. The theory is supported by a set of validation measurements when

  9. Imaging and characterizing root systems using electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Kemna, A.; Weigand, M.; Kelter, M.; Pfeifer, J.; Zimmermann, E.; Walter, A.

    2011-12-01

    Root architecture, growth, and activity play an essential role regarding the nutrient uptake of roots in soils. While in recent years advances could be achieved concerning the modeling of root systems, measurement methods capable of imaging, characterizing, and monitoring root structure and dynamics in a non-destructive manner are still lacking, in particular at the field scale. We here propose electrical impedance tomography (EIT) for the imaging of root systems. The approach takes advantage of the low-frequency capacitive electrical properties of the soil-root interface and the root tissue. These properties are based on the induced migration of ions in an externally applied electric field and give rise to characteristic impedance spectra which can be measured by means of electrical impedance spectroscopy. The latter technique was already successfully applied in the 10 Hz to 1 MHz range by Ozier-Lafontaine and Bajazet (2005) to monitor root growth of tomato. We here apply the method in the 1 mHz to 45 kHz range, requiring four-electrode measurements, and demonstrate its implementation and potential in an imaging framework. Images of real and imaginary components of complex electrical conductivity are computed using a finite-element based inversion algorithm with smoothness-constraint regularization. Results from laboratory measurements on rhizotrons with different root systems (barley, rape) show that images of imaginary conductivity delineate the spatial extent of the root system under investigation, while images of real conductivity show a less clear response. As confirmed by numerical simulations, the latter could be explained by the partly compensating electrical conduction properties of epidermis (resistive) and inner root cells (conductive), indicating the limitations of conventional electrical resistivity tomography. The captured spectral behavior exhibits two distinct relaxation processes with Cole-Cole type signatures, which we interpret as the responses

  10. [A Digital System for Bioimpedance and Electrical Impedance Tomography Measurement System].

    PubMed

    Chen, Xiaoyan; Gao, Nana; Huang, Huafang

    2015-06-01

    A digital system for bioimpedance and electrical impedance tomography (EIT) measurement controlled by an ATmega16 microcontroller was constructed in our laboratory. There are eight digital electrodes using AD5933 to measure the impedance of the targets, and the data is transmitted to the computer wirelessly through nRF24L01. The structure of the system, circuit design, system testing, vitro measurements of animals' tissues and electrical impedance tomography are introduced specifically in this paper. The experimental results showed that the system relative error was 0.42%, and the signal noise ratio was 76.3 dB. The system not only can be used to measure the impedance by any two electrodes within the frequency of 1-100 kHz in a sweep scanning, but also can reconstruct the images of EIT. The animal experiments showed that the data was valid and plots were fitting with Cole-Cole theory. The testing verified the feasibility and effectiveness of the system. The images reconstructed of a salt-water tank are satisfactory and match with the actual distribution of the tank. The system improves the effectiveness of the front-end measuring signal and the stability of the system greatly. PMID:26485981

  11. Using electrical impedance tomography to map subsurface hydraulic conductivity

    DOEpatents

    Berryman, James G.; Daily, William D.; Ramirez, Abelardo L.; Roberts, Jeffery J.

    2000-01-01

    The use of Electrical Impedance Tomography (EIT) to map subsurface hydraulic conductivity. EIT can be used to map hydraulic conductivity in the subsurface where measurements of both amplitude and phase are made. Hydraulic conductivity depends on at least two parameters: porosity and a length scale parameter. Electrical Resistance Tomography (ERT) measures and maps electrical conductivity (which can be related to porosity) in three dimensions. By introducing phase measurements along with amplitude, the desired additional measurement of a pertinent length scale can be achieved. Hydraulic conductivity controls the ability to flush unwanted fluid contaminants from the surface. Thus inexpensive maps of hydraulic conductivity would improve planning strategies for subsequent remediation efforts. Fluid permeability is also of importance for oil field exploitation and thus detailed knowledge of fluid permeability distribution in three-dimension (3-D) would be a great boon to petroleum reservoir analysts.

  12. Electrical impedance tomography and the fast multipole method

    NASA Astrophysics Data System (ADS)

    Bikowski, Jutta; Mueller, Jennifer L.

    2004-10-01

    A 3-D linearization-based reconstruction algorithm for Electrical Impedance Tomography suitable for breast cancer detection using data collected on a rectangular array was introduced by Mueller et al. [IEEE Biomed. Eng., 46(11), 1999]. By considering the scenario as an electrostatic problem, it is possible to model the electrodes with various charges, facilitating the use of the Fast Multipole Method (FMM) for calculating particle interactions and also supporting the use of different electrode models. In this paper the use of FMM is explained and results in form of reconstructed images from experimental data show that this method is an improvement.

  13. A new method for measuring osteoclast formation by electrical impedance.

    PubMed

    Emori, Haruka; Iwai, Shinichi; Ryu, Kakei; Amano, Hitoshi; Sambe, Takehiko; Kobayashi, Takahiro; Oguchi, Tatsunori; Ohura, Kiyoshi; Oguchi, Katsuji

    2015-06-01

    Osteoclasts are important target cells for osteoporosis treatment. Recently, a real-time cell analysis (RTCA) system was developed to observe cell morphology and adhesion; however, the use of RTCA to study osteoclastogenesis has not been reported. Here, we investigated whether osteoclast formation could be monitored in real-time using RTCA. The cell index determined via electrical impedance using RTCA, and the number of osteoclasts exhibited a significant positive correlation. RTCA was useful for determining the effect of (-)-epigallocatechin-3-gallate on the inhibition of bone resorption. We established a new method of measuring osteoclast formation in real-time using RTCA. PMID:26032840

  14. Electrical Impedance Spectroscopy as Electrical Biopsy for Monitoring Radiation Sequelae of Intestine in Rats

    PubMed Central

    Chao, Pei-Ju; Huang, Eng-Yen; Cheng, Kuo-Sheng; Huang, Yu-Jie

    2013-01-01

    Electrical impedance is one of the most frequently used parameters for characterizing material properties. The resistive and capacitive characteristics of tissue may be revealed by electrical impedance spectroscopy (EIS) as electrical biopsy. This technique could be used to monitor the sequelae after irradiation. In this study, rat intestinal tissues after irradiation were assessed by EIS system based on commercially available integrated circuits. The EIS results were fitted to a resistor-capacitor circuit model to determine the electrical properties of the tissue. The variations in the electrical characteristics of the tissue were compared to radiation injury score (RIS) by morphological and histological findings. The electrical properties, based on receiver operation curve (ROC) analysis, strongly reflected the histological changes with excellent diagnosis performance. The results of this study suggest that electrical biopsy reflects histological changes after irradiation. This approach may significantly augment the evaluation of tissue after irradiation. It could provide rapid results for decision making in monitoring radiation sequelae prospectively. PMID:24093111

  15. Active electrode IC for EEG and electrical impedance tomography with continuous monitoring of contact impedance.

    PubMed

    Guermandi, Marco; Cardu, Roberto; Franchi Scarselli, Eleonora; Guerrieri, Roberto

    2015-02-01

    The IC presented integrates the front-end for EEG and Electrical Impedance Tomography (EIT) acquisition on the electrode, together with electrode-skin contact impedance monitoring and EIT current generation, so as to improve signal quality and integration of the two techniques for brain imaging applications. The electrode size is less than 2 cm(2) and only 4 wires connect the electrode to the back-end. The readout circuit is based on a Differential Difference Amplifier and performs single-ended amplification and frequency division multiplexing of the three signals that are sent to the back-end on a single wire which also provides power supply. Since the system's CMRR is a function of each electrode's gain accuracy, an analysis is performed on how this is influenced by mismatches in passive and active components. The circuit is fabricated in 0.35 μm CMOS process and occupies 4 mm(2), the readout circuit consumes 360 μW, the input referred noise for bipolar EEG signal acquisition is 0.56 μVRMS between 0.5 and 100 Hz and almost halves if only EEG signal is acquired. PMID:24860040

  16. Body Fat Measurement: Weighing the Pros and Cons of Electrical Impedance.

    ERIC Educational Resources Information Center

    Nash, Heyward L.

    1985-01-01

    Research technologists have developed electrical impedance units in response to demand for a convenient and reliable method of measuring body fat. Accuracy of impedance measures versus calipers and underwater weighing are discussed. (MT)

  17. Microfluidic Impedance Flow Cytometry Enabling High-Throughput Single-Cell Electrical Property Characterization

    PubMed Central

    Chen, Jian; Xue, Chengcheng; Zhao, Yang; Chen, Deyong; Wu, Min-Hsien; Wang, Junbo

    2015-01-01

    This article reviews recent developments in microfluidic impedance flow cytometry for high-throughput electrical property characterization of single cells. Four major perspectives of microfluidic impedance flow cytometry for single-cell characterization are included in this review: (1) early developments of microfluidic impedance flow cytometry for single-cell electrical property characterization; (2) microfluidic impedance flow cytometry with enhanced sensitivity; (3) microfluidic impedance and optical flow cytometry for single-cell analysis and (4) integrated point of care system based on microfluidic impedance flow cytometry. We examine the advantages and limitations of each technique and discuss future research opportunities from the perspectives of both technical innovation and clinical applications. PMID:25938973

  18. Fully Parallel Electrical Impedance Tomography Using Code Division Multiplexing.

    PubMed

    Tsoeu, M S; Inggs, M R

    2016-06-01

    Electrical Impedance Tomography (EIT) has been dominated by the use of Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM) as methods of achieving orthogonal injection of excitation signals. Code Division Multiplexing (CDM), presented in this paper is an alternative that eliminates temporal data inconsistencies of TDM for fast changing systems. Furthermore, this approach eliminates data inconsistencies that arise in FDM when frequency bands of current injecting electrodes are chosen over frequencies that have large changes in the imaged object's impedance. To the authors knowledge no fully functional wideband system or simulation platform using simultaneous injection of Gold codes currents has been reported. In this paper, we formulate, simulate and develop a fully functional pseudo-random (Gold) code driven EIT system with 15 excitation currents and 16 separate voltage measurement electrodes. In the work we verify the use of CDM as a multiplexing modality in simultaneous injection EIT, using a prototype system with an overall bandwidth of 15 kHz, and attainable speed of 462 frames/s using codes with a period of 31 chips. Simulations and experiments are performed using the Electrical Impedance and Diffuse Optics Reconstruction Software (EIDORS). We also propose the use of image processing on reconstructed images to establish their quality quantitatively without access to raw reconstruction data. The results of this study show that CDM can be successfully used in EIT, and gives results of similar visual quality to TDM and FDM. Achieved performance shows average position error of 3.5% and size error of 6.2%. PMID:26731774

  19. Inversion without Explicit Jacobian Calculations in Electrical Impedance Tomography

    NASA Astrophysics Data System (ADS)

    Fouchard, A.; Bonnet, S.; Hervé, L.; David, O.

    2014-10-01

    Electrical impedance tomography (EIT) is the inverse problem of finding the internal conductivity distribution of a medium given boundary electrical measurements performed via an electrode array onto its surface. Conventional inversion schemes adopt Tikhonov regularized Newton-type methods. Following a transport back-transport approach, we develop in this work an adjoint approach which allows reducing computational burden in enabling inversion without explicit Jacobian calculation. Forward and back-projection operators are defined from potential gradients, along with their efficient implementation. These derivations allow the transparent use of inversion algorithms. We first check the implementation of operators. We then evaluate how reconstructions perform on simulated noisy data using a preconditioned conjugate gradient. We eventually practice our inversion framework on experimental data acquired in vitro from a saline phantom.

  20. Field Evaluation of Broadband Electrical Impedance Tomography Measurements

    NASA Astrophysics Data System (ADS)

    Kelter, M.; Huisman, J. A.; Zimmermann, E.; Treichel, A.; Kemna, A.; Vereecken, H.

    2014-12-01

    Laboratory measurements of the complex electrical conductivity in a broad frequency range (i.e. mHz to kHz) using spectral induced polarization (SIP) measurements have shown great promise to characterize important hydrological properties (e.g. hydraulic conductivity) and biogeochemical processes. However, translating these findings to field applications remains challenging, and significant improvements in spectral electrical impedance tomography (EIT) are still required to obtain images of the complex electrical conductivity with sufficient accuracy in the field. The aim of this study is to present recent improvements in the inversion and processing of broadband field EIT measurements, and to evaluate the accuracy and spectral consistency of the obtained images of the real and imaginary part of the electrical conductivity. In a first case study, time-lapse surface EIT measurements were performed during an infiltration experiment to investigate the spectral complex electrical conductivity as a function of water content. State-of-the-art data processing and inversion approaches were used to obtain images of the complex electrical conductivity in a frequency range of 100 mHz to 1 kHz, and integral parameters were obtained using Debye decomposition. Results showed consistent spectral and spatial variation of the phase of the complex electrical conductivity in a broad frequency range, and a complex dependence on water saturation that was reasonably consistent with laboratory EIT measurements. In a second case study, borehole EIT measurements were made in a well-characterized aquifer. These measurements were inverted to obtain broadband images of the complex conductivity after correction for inductive and capacitive coupling using recently developed procedures. The results showed good correspondence with reference laboratory SIP measurements in a broad frequency bandwidth up to 1 kHz only after application of the correction procedures.

  1. Fractional calculus model of electrical impedance applied to human skin.

    PubMed

    Vosika, Zoran B; Lazovic, Goran M; Misevic, Gradimir N; Simic-Krstic, Jovana B

    2013-01-01

    Fractional calculus is a mathematical approach dealing with derivatives and integrals of arbitrary and complex orders. Therefore, it adds a new dimension to understand and describe basic nature and behavior of complex systems in an improved way. Here we use the fractional calculus for modeling electrical properties of biological systems. We derived a new class of generalized models for electrical impedance and applied them to human skin by experimental data fitting. The primary model introduces new generalizations of: 1) Weyl fractional derivative operator, 2) Cole equation, and 3) Constant Phase Element (CPE). These generalizations were described by the novel equation which presented parameter [Formula: see text] related to remnant memory and corrected four essential parameters [Formula: see text] We further generalized single generalized element by introducing specific partial sum of Maclaurin series determined by parameters [Formula: see text] We defined individual primary model elements and their serial combination models by the appropriate equations and electrical schemes. Cole equation is a special case of our generalized class of models for[Formula: see text] Previous bioimpedance data analyses of living systems using basic Cole and serial Cole models show significant imprecisions. Our new class of models considerably improves the quality of fitting, evaluated by mean square errors, for bioimpedance data obtained from human skin. Our models with new parameters presented in specific partial sum of Maclaurin series also extend representation, understanding and description of complex systems electrical properties in terms of remnant memory effects. PMID:23577065

  2. Fractional Calculus Model of Electrical Impedance Applied to Human Skin

    PubMed Central

    Vosika, Zoran B.; Lazovic, Goran M.; Misevic, Gradimir N.; Simic-Krstic, Jovana B.

    2013-01-01

    Fractional calculus is a mathematical approach dealing with derivatives and integrals of arbitrary and complex orders. Therefore, it adds a new dimension to understand and describe basic nature and behavior of complex systems in an improved way. Here we use the fractional calculus for modeling electrical properties of biological systems. We derived a new class of generalized models for electrical impedance and applied them to human skin by experimental data fitting. The primary model introduces new generalizations of: 1) Weyl fractional derivative operator, 2) Cole equation, and 3) Constant Phase Element (CPE). These generalizations were described by the novel equation which presented parameter related to remnant memory and corrected four essential parameters We further generalized single generalized element by introducing specific partial sum of Maclaurin series determined by parameters We defined individual primary model elements and their serial combination models by the appropriate equations and electrical schemes. Cole equation is a special case of our generalized class of models for Previous bioimpedance data analyses of living systems using basic Cole and serial Cole models show significant imprecisions. Our new class of models considerably improves the quality of fitting, evaluated by mean square errors, for bioimpedance data obtained from human skin. Our models with new parameters presented in specific partial sum of Maclaurin series also extend representation, understanding and description of complex systems electrical properties in terms of remnant memory effects. PMID:23577065

  3. Effect of borehole design on electrical impedance tomography measurements

    NASA Astrophysics Data System (ADS)

    Mozaffari, Amirpasha; Huisman, Johan Alexander; Treichel, Andrea; Zimmermann, Egon; Kelter, Matthias; Vereecken, Harry

    2015-04-01

    Electrical Impedance Tomography (EIT) is a sophisticated non-invasive tool to investigate the subsurface in engineering and environmental studies. To increase the depth of investigation, EIT measurements can be made in boreholes. However, the presence of the borehole may affect EIT measurements. Here, we aim to investigate the effect of different borehole components on EIT measurements using 2,5-D and 3D finite element modeling and unstructured meshes. To investigate the effect of different borehole components on EIT measurements, a variety of scenarios were designed. In particular, the effect of the water-filled borehole, the PVC casing, and the gravel filter were investigated relative to complex resistivity simulations for a homogenous medium with chain and electrode modules. It was found that the results of the complex resistivity simulations were best understood using the sensitivity distribution of the electrode configuration under consideration. In all simulations, the sensitivity in the vicinity of the borehole was predominantly negative. Therefore, the introduction of the water-filled borehole caused an increase in the real part of the impedance, and a decrease (more negative) in the imaginary part of the simulated impedance. The PVC casing mostly enhanced the effect of the water-filled borehole described above, although this effect was less clear for some electrode configuration. The effect of the gravel filter mostly reduced the effect of the water-filled borehole with PVC casing. For EIT measurements in a single borehole, the highest simulated phase error was 12% for a Wenner configuration with electrode spacing of 0.33 m. This error decreased with increasing electrode spacing. In the case of cross-well configurations, the error in the phase shit was as high as 6%. Here, it was found that the highest errors occur when both current electrodes are located in the same borehole. These results indicated that cross-well measurements are less affected by the

  4. Using electrical impedance spectroscopy to detect water in planetary regoliths.

    PubMed

    Seshadri, Suresh; Chin, Keith B; Buehler, Martin G; Anderson, Robert C

    2008-08-01

    We present data in examination of the utility of electrical impedance spectroscopy measurements for in situ surveys to determine the water content, distribution, and phase in unconsolidated planetary regolith. We conducted calibration experiments under conditions relevant to Mars: the concentration of electrolytes in solution was varied up to 1 M to simulate the effects of unsaturated dissolved minerals and brines. We also varied the water content of heterogeneous water/sand mixtures, made with these electrolytic solutions from 0.01 wt% to 10 wt%. Tests were performed at temperatures from +25 degrees C to -65 degrees C. Conductivity and dielectric permittivity calculated from the impedance measurements indicate an expected dependence on electrolyte concentration and relative independence from electrolyte type for both liquid water and water ice. Conductivity and calculated dielectric relaxation times for these aqueous solutions agree with existing data in the literature. The relative permittivity for heterogeneous water/sand mixtures is dominated by polarization effects for the electrode configuration used. However, the characteristic orientational relaxation of ice is still visible. The conductivity retains the strong dependence on electrolyte concentration, and the permittivity is still not affected by electrolyte type. A "universal" curve between conductivity and water content establishes detectability limits of <0.01 wt% and approximately 0.3 wt% for water/sand mixtures containing liquid water and ice, respectively. PMID:18752458

  5. Determinants of pulmonary perfusion measured by electrical impedance tomography.

    PubMed

    Smit, Henk J; Vonk Noordegraaf, Anton; Marcus, J Tim; Boonstra, Anco; de Vries, Peter M; Postmus, Pieter E

    2004-06-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technique for detecting blood volume changes that can visualize pulmonary perfusion. The two studies reported here tested the hypothesis that the size of the pulmonary microvascular bed, rather than stroke volume (SV), determines the EIT signal. In the first study, the impedance changes relating to the maximal pulmonary pulsatile blood volume during systole (Delta Z(sys)) were measured in ten healthy subjects, ten patients diagnosed with chronic obstructive pulmonary disease, who were considered to have a reduced pulmonary vascular bed, and ten heart failure patients with an assumed low cardiac output but with a normal lung parenchyma. Mean Delta Z(sys) (SD) in these groups was 261 (34)x10(-5), 196 (39)x10(-5) ( P<0.001) and 233 (61)x10(-5) arbitrary units (AU) (P=NS), respectively. In the second study, including seven healthy volunteers, Delta Z(sys) was measured at rest and during exercise on a recumbent bicycle while SV was measured by means of magnetic resonance imaging. The Delta Z(sys) at rest was 352 (53)x10(-5 ) and 345 (112)x10(-5 )AU during exercise (P=NS), whereas SV increased from 83 (21) to 105 (34) ml (P<0.05). The EIT signal likely reflects the size of the pulmonary microvascular bed, since neither a low cardiac output nor a change in SV of the heart appear to influence EIT. PMID:14985995

  6. Recent progress on the factorization method for electrical impedance tomography.

    PubMed

    Harrach, Bastian

    2013-01-01

    The Factorization Method is a noniterative method to detect the shape and position of conductivity anomalies inside an object. The method was introduced by Kirsch for inverse scattering problems and extended to electrical impedance tomography (EIT) by Brühl and Hanke. Since these pioneering works, substantial progress has been made on the theoretical foundations of the method. The necessary assumptions have been weakened, and the proofs have been considerably simplified. In this work, we aim to summarize this progress and present a state-of-the-art formulation of the Factorization Method for EIT with continuous data. In particular, we formulate the method for general piecewise analytic conductivities and give short and self-contained proofs. PMID:24069064

  7. Electrical impedance tomography of the 1995 OGI perchloroethelyne release

    SciTech Connect

    Dailey, W.; Ramirez, A.

    1996-10-01

    Goal is to determine if electrical impedance tomography (EIT) might be useful to map free product DNAPL (dense nonaqueous phase liquids) contamination. EIT was used to image the plume resulting from a release of 189 liters (50 gallons) of perchloroethylene (PCE) into a saturated aquifer constructed of sand with two layers of bentonite. Images were made in 4 planes, before, during, and after the release, to generate a detailed picture of the spatial and temporal development of the plume. Information of the EI (both in phase and out of phase voltages) was used at several different frequencies to produce images. Some frequency dispersion was observed in the images before and after the PCE release. Laboratory measurements of organic contamination in soil indicate detectable dispersion. A search for this effect in EIT images reveals weak evidence, the signal appearing just above the measurement uncertainty, of a change in the reactance in the soil because of the PCE.

  8. Automated robust test framework for electrical impedance tomography.

    PubMed

    Gaggero, Pascal O; Adler, Andy; Waldmann, Andreas D; Mamatjan, Yasin; Justiz, Jörn; Koch, Volker M

    2015-06-01

    An automated test system and procedure is proposed, designed to enable systematic testing of electrical impedance tomography (EIT) devices. The system is designed to calculate reliable, repeatable and accurate performance figures of merit of an EIT system using a saline phantom and an industrial robot arm. Applications of the test system are to compare EIT devices against requirements, or to help optimize a device for its operating parameters. A test methodology and sample test results are presented to illustrate its use. The system is used to compare image quality and contrast detection for a range of stimulation and measurement patterns, and results show the best images when the pair of current injection electrodes is spaced between 45 and 170 degrees on a tank. Finally, we propose a classification of the object detection errors, which can facilitate comparison of EIT instrument specifications. PMID:26009262

  9. Toward Microendoscopic Electrical Impedance Tomography for Intraoperative Surgical Margin Assessment

    PubMed Central

    Halter, Ryan J.; Kim, Young-Joong

    2015-01-01

    No clinical protocols are routinely used to intraoperatively assess surgical margin status during prostate surgery. Instead, margins are evaluated through pathological assessment of the prostate following radical prostatectomy, when it is too late to provide additional surgical intervention. An intraoperative device potentially capable of assessing surgical margin status based on the electrical property contrast between benign and malignant prostate tissue has been developed. Specifically, a microendoscopic electrical impedance tomography (EIT) probe has been constructed to sense and image, at near millimeter resolution, the conductivity contrast within heterogeneous biological tissues with the goal of providing surgeons with real-time assessment of margin pathologies. This device consists of a ring of eight 0.6-mm diameter electrodes embedded in a 5-mm diameter probe tip to enable access through a 12-mm laparoscopic port. Experiments were performed to evaluate the volume of tissue sensed by the probe. The probe was also tested with inclusions in gelatin, as well as on a sample of porcine tissue with clearly defined regions of adipose and muscle. The probe's area of sensitivity consists of a circular area of 9.1 mm2 and the maximum depth of sensitivity is approximately 1.5 mm. The probe is able to distinguish between high contrast muscle and adipose tissue on a sub-mm scale (~500 μm). These preliminary results suggest that EIT is possible in a probe designed to fit within a 12-mm laparoscopic access port. PMID:24951675

  10. Transthoracic Electrical Impedance in Cases of High-altitude Hypoxia

    PubMed Central

    Roy, Sujoy B.; Balasubramanian, V.; Khan, M. R.; Kaushik, V. S.; Manchanda, S. C.; Guha, S. K.

    1974-01-01

    Changes in transthoracic electrical impedance (T.E.I.) due to high-altitude hypoxia (3,658 m) have been measured in 20 young, healthy Indian soldiers. They were first studied at sea level (198 m) and then rapidly transported by air to 3,658 m, where they were studied daily from day 1 to day 5 and then on days 8 and 10. The mean (±S.D.) T.E.I. at sea level (34·6±0·6Ω) fell sharply to 29·6±0·8Ω, 30·3±0·9Ω, and 30·5±1·1Ω on days 1, 2, and 3 (P <0·001) and levelled off at 31·5±0·7Ω on day 10, which was comparable to the mean value obtained in 13 persons permanently resident at high altitude (32·2±0·7Ω). Five sea-level residents who had acute mountain sickness (A.M.S.) or high-altitude pulmonary oedema (H.A.P.O.) had a still lower mean value (22·5±1·1Ω). One normal healthy subject who at sea level had a T.E.I. of 34·7Ω developed H.A.P.O. when the T.E.I. fell to 21·1Ω. Ninety minutes after the administration of 80 mg of intravenous frusemide the value increased to 35·5Ω. In another subject with A.M.S. who received 40 mg of frusemide intravenously the T.E.I. rose from 21·9 to 33·2Ω. Since the study was non-invasive the changes in impedance could not be correlated objectively with alterations in either pulmonary blood volume or pulmonary extravascular water space. In the subject, however, with x-ray evidence of H.A.P.O. and a low T.E.I. intravenous frusemide produced a marked rise in T.E.I. together with clearing of the chest x-ray picture within 24 hours, indicating an inverse relationship between impedance and thoracic fluid volume. It is suggested that with further objective verification in man the measurement of T.E.I. may be a potentially promising technique for the early detection of increased pulmonary fluid volume. ImagesFIG. 3FIG. 4 PMID:4416705

  11. Acousto-electric impedance of ferroelectric phononic superlattice

    NASA Astrophysics Data System (ADS)

    Nusierat, Ola Hassan

    The acousto-electric impedance Z(ƒ) of a ferroelectric phononic superlattice (FPS) is investigated. The analytical derivation of Z(ƒ) and its phase reveal that both are functions of physical parameters such as the electromechanical coupling coefficient, the mechanical quality factor, the domain length and the phase velocity of the plate acoustic waves (PAW). Mathematica code is produced that allows for modeling Z(ƒ) in a two dimensional FPS. It is observed that Z(ƒ) depends on the number of domains in the FPS structure. Fewer domains in the structure might minimize Z(ƒ) or make it approach zero at certain conditions. A series of experiments is performed to investigate the impedance and its phase shift for a ZX-cut periodically poled lithium niobate in the frequency range 3-4 MHz. The experimental results of studying Z(ƒ) and its phase shift are in a good agreement with the developed theory. Experiments reveal the stopband, when an acoustic wavelength is close to a double-length of ferroelectric domain within the inversely poled structure, in which Z(ƒ) has minima close to it. Furthermore, these experiments show that the displacement components of the acoustic mode are decoupled in the transition zone, a small frequency range that extends a few kilohertz from the boundary of the stopband, and the amplitude of those decoupled components goes to zero in that zone. The equations obtained, the computation codes developed, and the experimental investigations can be applied to the ultrasonic transducers and the field of energy harvesting.

  12. Using impedance measurements for detecting pathogens trapped in an electric field

    DOEpatents

    Miles, Robin R.

    2004-07-20

    Impedance measurements between the electrodes in an electric field is utilized to detect the presence of pathogens trapped in the electric field. Since particles trapped in a field using the dielectiphoretic force changes the impedance between the electrodes by changing the dielectric material between the electrodes, the degree of particle trapping can be determined by measuring the impedance. This measurement is used to determine if sufficient pathogen have been collected to analyze further or potentially to identify the pathogen.

  13. Comparison of total variation algorithms for electrical impedance tomography.

    PubMed

    Zhou, Zhou; Sato dos Santos, Gustavo; Dowrick, Thomas; Avery, James; Sun, Zhaolin; Xu, Hui; Holder, David S

    2015-06-01

    The applications of total variation (TV) algorithms for electrical impedance tomography (EIT) have been investigated. The use of the TV regularisation technique helps to preserve discontinuities in reconstruction, such as the boundaries of perturbations and sharp changes in conductivity, which are unintentionally smoothed by traditional l2 norm regularisation. However, the non-differentiability of TV regularisation has led to the use of different algorithms. Recent advances in TV algorithms such as the primal dual interior point method (PDIPM), the linearised alternating direction method of multipliers (LADMM) and the spilt Bregman (SB) method have all been demonstrated successful EIT applications, but no direct comparison of the techniques has been made. Their noise performance, spatial resolution and convergence rate applied to time difference EIT were studied in simulations on 2D cylindrical meshes with different noise levels, 2D cylindrical tank and 3D anatomically head-shaped phantoms containing vegetable material with complex conductivity. LADMM had the fastest calculation speed but worst resolution due to the exclusion of the second-derivative; PDIPM reconstructed the sharpest change in conductivity but with lower contrast than SB; SB had a faster convergence rate than PDIPM and the lowest image errors. PMID:26008768

  14. Frequency-difference electrical impedance tomography: Phantom imaging experiments

    NASA Astrophysics Data System (ADS)

    Ahn, Sujin; Jun, Sung Chan; Seo, Jin Keun; Lee, Jeehyun; Woo, Eung Je; Holder, David

    2010-04-01

    Frequency-difference electrical impedance tomography (fdEIT) using a weighted voltage difference has been proposed as a means to provide images of admittivity changes at different frequencies. This weighted difference method is an effective way to extract anomaly information while eliminating background effects by unknown boundary geometry, uncertainty in electrode positions and other systematic measurement artefacts. It also properly handles the interplay between conductivity and permittivity in measured boundary voltage data. Though the proposed fdEIT algorithm is promising for applications such as detection of hemorrhagic stroke and breast cancer, more validation studies are needed. In this paper, we performed two-and three-dimensional numerical simulations and phantom experiments. Backgrounds of imaging objects were either saline or carrot pieces suspended in saline. We used carrot pieces to simulate a more realistic frequency-dependent admittivity distribution. Test objects were banana, potato or conductive gel with known admittivity spectra. When the background was saline, both simple and weighted difference approaches produced reasonably accurate images. The weighted difference method yielded better images from two-dimensional imaging objects with background of carrot pieces. For the three-dimensional head-shaped phantom, the advantage of the weighted frequency difference method over the simple difference method is not as obvious as in the case of the two-dimensional phantom. It is unclear if this is due to measurement errors or limitations in the linear algorithm. Further refinement and validation of the frequency difference image reconstructions are currently in progress.

  15. Influence of volume and flow change on the electrical impedance signal (in vitro)

    NASA Astrophysics Data System (ADS)

    Bodo, M.; Garcia, A.; Pearce, F.; Van Albert, S.; Armonda, R.

    2010-04-01

    On the basis of preliminary results, rheoencephalography (REG) shows promise as a practical, noninvasive and continuous monitoring modality of brain injuries. However, REG literature reflects uncertainty about whether the signal reflects flow or volume. Presented here are results of in vitro studies manipulating flow/volume to model clinical conditions (such as brain ischemia and vasospasm) while recording the electrical impedance signal. A loop was created using tubing filled with 0.9 % NaCl. This loop was comprised of a Doppler in-line flow probe connected to an ultrasound flow meter, a peristaltic pump, a pressure transducer and home-made electrical impedance measuring cell, incorporating a balloon catheter. Bipolar impedance amplifiers were used for measuring impedance pulse waves. Data were stored on a PC and processed off-line. This in vitro study confirmed that 1) Doubling flow rate influenced the pulse amplitude and mean flow of the Doppler signal; 2) Doubling flow rate had no influence on the amplitudes of the pressure or electrical impedance signals; 3) An increase in amplitude was observed in the pressure and electrical impedance signals when the first derivative was taken. 4) Balloon inflation decreased electrical impedance and Doppler flow pulse amplitudes; 5) With balloon inflation, Doppler and electrical impedance signals showed an identical relationship to decreased flow (R2=0.966).

  16. Electric fields in Scanning Electron Microscopy simulations

    NASA Astrophysics Data System (ADS)

    Arat, K. T.; Bolten, J.; Klimpel, T.; Unal, N.

    2016-03-01

    The electric field distribution and charging effects in Scanning Electron Microscopy (SEM) were studied by extending a Monte-Carlo based SEM simulator by a fast and accurate multigrid (MG) based 3D electric field solver. The main focus is on enabling short simulation times with maintaining sufficient accuracy, so that SEM simulation can be used in practical applications. The implementation demonstrates a gain in computation speed, when compared to a Gauss-Seidel based reference solver is roughly factor of 40, with negligible differences in the result (~10-6 𝑉). In addition, the simulations were compared with experimental SEM measurements using also complex 3D sample, showing that i) the modelling of e-fields improves the simulation accuracy, and ii) multigrid method provide a significant benefit in terms of simulation time.

  17. Calibrated complex impedance of CHO cells and E. coli bacteria at GHz frequencies using scanning microwave microscopy

    NASA Astrophysics Data System (ADS)

    Tuca, Silviu-Sorin; Badino, Giorgio; Gramse, Georg; Brinciotti, Enrico; Kasper, Manuel; Oh, Yoo Jin; Zhu, Rong; Rankl, Christian; Hinterdorfer, Peter; Kienberger, Ferry

    2016-04-01

    The application of scanning microwave microscopy (SMM) to extract calibrated electrical properties of cells and bacteria in air is presented. From the S 11 images, after calibration, complex impedance and admittance images of Chinese hamster ovary cells and E. coli bacteria deposited on a silicon substrate have been obtained. The broadband capabilities of SMM have been used to characterize the bio-samples between 2 GHz and 20 GHz. The resulting calibrated cell and bacteria admittance at 19 GHz were Y cell = 185 μS + j285 μS and Y bacteria = 3 μS + j20 μS, respectively. A combined circuitry-3D finite element method EMPro model has been developed and used to investigate the frequency response of the complex impedance and admittance of the SMM setup. Based on a proposed parallel resistance-capacitance model, the equivalent conductance and parallel capacitance of the cells and bacteria were obtained from the SMM images. The influence of humidity and frequency on the cell conductance was experimentally studied. To compare the cell conductance with bulk water properties, we measured the imaginary part of the bulk water loss with a dielectric probe kit in the same frequency range resulting in a high level of agreement.

  18. Calibrated complex impedance of CHO cells and E. coli bacteria at GHz frequencies using scanning microwave microscopy.

    PubMed

    Tuca, Silviu-Sorin; Badino, Giorgio; Gramse, Georg; Brinciotti, Enrico; Kasper, Manuel; Oh, Yoo Jin; Zhu, Rong; Rankl, Christian; Hinterdorfer, Peter; Kienberger, Ferry

    2016-04-01

    The application of scanning microwave microscopy (SMM) to extract calibrated electrical properties of cells and bacteria in air is presented. From the S 11 images, after calibration, complex impedance and admittance images of Chinese hamster ovary cells and E. coli bacteria deposited on a silicon substrate have been obtained. The broadband capabilities of SMM have been used to characterize the bio-samples between 2 GHz and 20 GHz. The resulting calibrated cell and bacteria admittance at 19 GHz were Y cell = 185 μS + j285 μS and Y bacteria = 3 μS + j20 μS, respectively. A combined circuitry-3D finite element method EMPro model has been developed and used to investigate the frequency response of the complex impedance and admittance of the SMM setup. Based on a proposed parallel resistance-capacitance model, the equivalent conductance and parallel capacitance of the cells and bacteria were obtained from the SMM images. The influence of humidity and frequency on the cell conductance was experimentally studied. To compare the cell conductance with bulk water properties, we measured the imaginary part of the bulk water loss with a dielectric probe kit in the same frequency range resulting in a high level of agreement. PMID:26895571

  19. Electrical impedance measurements: rapid method for detecting and monitoring microorganisms.

    PubMed Central

    Cady, P; Dufour, S W; Shaw, J; Kraeger, S J

    1978-01-01

    A conceptually simple and east-to-use technique is described that uses continuous impedance measurements for automated monitoring of microbial growth and metabolism. The method has been applied to a wide range of microorganisms. Optical clarity is not required. The sensitivity and reproducibility of the method are demonstrated. The mechanism whereby microbial growth alters the impedance of the medium is discussed, as well as potential applications of the method to clinical microbiology. Images PMID:348718

  20. Investigation of electrical properties of Mn doped tin oxide nanoparticles using impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Azam, Ameer; Ahmed, Arham S.; Chaman, M.; Naqvi, A. H.

    2010-11-01

    Manganese doped tin oxide nanoparticles with manganese content varying from 0 to 15 mol % were synthesized using sol-gel method. The structural and compositional analysis was carried out using x-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive x-ray analysis (EDAX). Dielectric and impedance spectroscopy was carried out at room temperature to explore the electrical properties of Mn doped SnO2. XRD analysis indicated the formation of single phase rutile type tetragonal structure of all the samples. The crystallite size was observed to vary from 16.2 to 7.1 nm as the Mn content was increased. The XRD, SEM, and EDAX results corroborated the successful doping of Mn in the SnO2 matrix. Complex impedance analysis was used to distinguish the grain and grain boundary contributions to the system, suggesting the dominance of grain boundary resistance in the doped samples. The dielectric constant ɛ', dielectric loss tan δ and ac conductivity σac were studied as a function of frequency and composition and the behavior has been explained on the basis of Maxwell-Wagner interfacial model. All the dielectric parameters were found to decrease with the increase in doping concentration. Moreover, it has been observed that the dielectric loss approaches to zero in case of high dopant concentration (9%, 15%) at high frequencies.

  1. Electrical Impedance of Acupuncture Meridians: The Relevance of Subcutaneous Collagenous Bands

    PubMed Central

    Ahn, Andrew C.; Park, Min; Shaw, Jessica R.; McManus, Claire A.; Kaptchuk, Ted J.; Langevin, Helene M.

    2010-01-01

    Background The scientific basis for acupuncture meridians is unknown. Past studies have suggested that acupuncture meridians are physiologically characterized by low electrical impedance and anatomically associated with connective tissue planes. We are interested in seeing whether acupuncture meridians are associated with lower electrical impedance and whether ultrasound-derived measures – specifically echogenic collagenous bands - can account for these impedance differences. Methods/Results In 28 healthy subjects, we assessed electrical impedance of skin and underlying subcutaneous connective tissue using a four needle-electrode approach. The impedances were obtained at 10 kHz and 100 kHz frequencies and at three body sites - upper arm (Large Intestine meridian), thigh (Liver), and lower leg (Bladder). Meridian locations were determined by acupuncturists. Ultrasound images were obtained to characterize the anatomical features at each measured site. We found significantly reduced electrical impedance at the Large Intestine meridian compared to adjacent control for both frequencies. No significant decrease in impedance was found at the Liver or Bladder meridian. Greater subcutaneous echogenic densities were significantly associated with reduced impedances in both within-site (meridian vs. adjacent control) and between-site (arm vs. thigh vs. lower leg) analyses. This relationship remained significant in multivariable analyses which also accounted for gender, needle penetration depth, subcutaneous layer thickness, and other ultrasound-derived measures. Conclusion/Significance Collagenous bands, represented by increased ultrasound echogenicity, are significantly associated with lower electrical impedance and may account for reduced impedances previously reported at acupuncture meridians. This finding may provide important insights into the nature of acupuncture meridians and the relevance of collagen in bioelectrical measurements. PMID:20689594

  2. A new application of electrical impedance spectroscopy for measuring glucose metabolism: a phantom study

    NASA Astrophysics Data System (ADS)

    Dhurjaty, Sreeram; Qiu, Yuchen; Tan, Maxine; Liu, Hong; Zheng, Bin

    2015-03-01

    Glucose metabolism relates to biochemical processes in living organisms and plays an important role in diabetes and cancer-metastasis. Although many methods are available for measuring glucose metabolism-activities, from simple blood tests to positron emission tomography, currently there is no robust and affordable device that enables monitoring of glucose levels in real-time. In this study we tested feasibility of applying a unique resonance-frequency based electronic impedance spectroscopy (REIS) device that has been, recently developed to measure and monitor glucose metabolism levels using a phantom study. In this new testing model, a multi-frequency electrical signal sequence is applied and scanned through the subject. When the positive reactance of an inductor inside the device cancels out the negative reactance of the capacitance of the subject, the electrical impedance reaches a minimum value and this frequency is defined as the resonance frequency. The REIS system has a 24-bit analog-to-digital signal convertor and a frequency-resolution of 100Hz. In the experiment, two probes are placed inside a 100cc container initially filled with distilled water. As we gradually added liquid-glucose in increments of 1cc (250mg), we measured resonance frequencies and minimum electrical signal values (where A/D was normalized to a full scale of 1V). The results showed that resonance frequencies monotonously decreased from 243kHz to 178kHz, while the minimum voltages increased from 405mV to 793mV as the added amount of glucose increased from 0 to 5cc. The study demonstrated the feasibility of applying this new REIS technology to measure and/or monitor glucose levels in real-time in future.

  3. Rapid detection of bacterial growth in blood samples by a continuous-monitoring electrical impedance apparatus.

    PubMed Central

    Specter, S; Throm, R; Strauss, R; Friedman, H

    1977-01-01

    A growth detection method utilizing an automated apparatus capable of rapidly detecting bacterial growth by measuring changes of electrical impedance in bacteriological medium was utilized with "mock" blood cultures containing various gram-negative and gram-positive bacteria. Measurement of changes of electrical impedance was found to ba as accurate and comparable for time of growth detection as the radiometric method for detection of the same bacteria using mock blood cultures. In a limited clinical trial the use of the electrical impedance apparatus detected in 1 positive specimen from 40 clinical blood specimens as rapidly as by radiometric measurement. Both methods were considerably faster for detecting bacterial growth as compared with conventional culture methods. The selected species of gram-positive and -negative organisms tested were all detected by the electrical impedance method, including aerobes and anerobes. However, addition of 5% CO2 to the incubation atmosphere enhanced detection of gram-positive organisms. PMID:336642

  4. Electrical stimulation causes rapid changes in electrode impedance of cell-covered electrodes

    PubMed Central

    Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Seligman, Peter; Cowan, Robert; Shepherd, Robert

    2011-01-01

    Animal and clinical observations of a reduction in electrode impedance following electrical stimulation encouraged the development of an in vitro model of the electrode-tissue interface. This model was used previously to show an increase in impedance with cell and protein cover over electrodes. In this paper, the model was used to assess the changes in electrode impedance and cell cover following application of a charge-balanced biphasic current pulse train. Following stimulation, a large and rapid drop in total impedance (Zt) and access resistance (Ra) occurred. The magnitude of this impedance change was dependent on the current amplitude used, with a linear relationship determined between Ra and the resulting cell cover over the electrodes. The changes in impedance due to stimulation were shown to be transitory, with impedance returning to pre-stimulation levels several hours after cessation of stimulation. A loss of cells over the electrode surface was observed immediately after stimulation suggesting that the level of stimulation applied was creating localised changes to cell adhesion. Similar changes in electrode impedance were observed for in vivo and in vitro work, thus helping to verify the in vitro model, although the underlying mechanisms may differ. A change in the porosity of the cellular layer was proposed to explain the alterations in electrode impedance in vitro. These in vitro studies provide insight into the possible mechanisms occurring at the electrode-tissue interface in association with electrical stimulation. PMID:21572219

  5. Electrical impedance tomography may optimize ventilation in a postpartum woman with respiratory failure.

    PubMed

    Karsten, J; Bohlmann, M K; Sedemund-Adib, B; Wnent, J; Paarmann, H; Iblher, P; Meier, T; Heinze, H

    2013-01-01

    Amniotic fluid embolism is a rare peripartum complication with the sudden onset of haemodynamic instability, respiratory failure and coagulopathy during labour or soon after delivery. A 31-year-old woman with amniotic fluid embolism was treated with vasopressors, inotropes, intravenous fluid, tranexamic acid and ventilatory support. Assessment of respiratory impairment was made using conventional chest X-ray, computed tomography and electrical impedance tomography. The potential for electrical impedance tomography to improve monitoring and guide respiratory therapy is explored. PMID:23122281

  6. Nonlinear electrical impedance spectroscopy of viruses using very high electric fields created by nanogap electrodes

    PubMed Central

    Hatsuki, Ryuji; Honda, Ayae; Kajitani, Masayuki; Yamamoto, Takatoki

    2015-01-01

    Our living sphere is constantly exposed to a wide range of pathogenic viruses, which can be either known, or of novel origin. Currently, there is no methodology for continuously monitoring the environment for viruses in general, much less a methodology that allows the rapid and sensitive identification of a wide variety of viruses responsible for communicable diseases. Traditional approaches, based on PCR and immunodetection systems, only detect known or specifically targeted viruses. We here describe a simple device that can potentially detect any virus between nanogap electrodes using nonlinear impedance spectroscopy. Three test viruses, differing in shape and size, were used to demonstrate the general applicability of this approach: baculovirus, tobacco mosaic virus (TMV), and influenza virus. We show that each of the virus types responded differently in the nanogap to changes in the electric field strength, and the impedance of the virus solutions differed depending both on virus type and virus concentration. These preliminary results show that the three virus types can be distinguished and their approximate concentrations determined. Although further studies are required, the proposed nonlinear impedance spectroscopy method may achieve a sensitivity comparable to that of more traditional, but less versatile, virus detection systems. PMID:26441875

  7. Imaging fast electrical activity in the brain with electrical impedance tomography

    PubMed Central

    Aristovich, Kirill Y.; Packham, Brett C.; Koo, Hwan; Santos, Gustavo Sato dos; McEvoy, Andy; Holder, David S.

    2016-01-01

    Imaging of neuronal depolarization in the brain is a major goal in neuroscience, but no technique currently exists that could image neural activity over milliseconds throughout the whole brain. Electrical impedance tomography (EIT) is an emerging medical imaging technique which can produce tomographic images of impedance changes with non-invasive surface electrodes. We report EIT imaging of impedance changes in rat somatosensory cerebral cortex with a resolution of 2 ms and < 200 μm during evoked potentials using epicortical arrays with 30 electrodes. Images were validated with local field potential recordings and current source-sink density analysis. Our results demonstrate that EIT can image neural activity in a volume 7 × 5 × 2 mm in somatosensory cerebral cortex with reduced invasiveness, greater resolution and imaging volume than other methods. Modeling indicates similar resolutions are feasible throughout the entire brain so this technique, uniquely, has the potential to image functional connectivity of cortical and subcortical structures. PMID:26348559

  8. Electrical impedance tomography spectroscopy method for characterising particles in solid-liquid phase

    NASA Astrophysics Data System (ADS)

    Zhao, Yanlin; Wang, Mi; Yao, Jun

    2014-04-01

    Electrical impedance tomography (EIT) is one of the process tomography techniques to provide an on-line non-invasive imaging for multiphase flow measurement. With EIT measurements, the images of impedance real part, impedance imaginary part, phase angle, and magnitude can be obtained. However, most of the applications of EIT in the process industries rely on the conductivity difference between two phases in fluids to obtain the concentration profiles. It is not common to use the imaginary part or phase angle due to the dominant change in conductivity or complication in the use of other impedance information. In a solid-liquid two phases system involving nano- or submicro-particles, characterisation of particles (e.g. particle size and concentration) have to rely on the measurement of impedance phase angle or imaginary part. Particles in a solution usually have an electrical double layer associated with their surfaces and can form an induced electrical dipole moment due to the polarization of the electrical double layer under the influence of an alternating electric field. Similar to EIT, electrical impedance spectroscopy (EIS) measurement can record the electrical impedance data, including impedance real part, imaginary part and phase angle (θ), which are caused by the polarization of the electrical double layer. These impedance data are related to the particle characteristics e.g. particle size, particle and ionic concentrations in the aqueous medium, therefore EIS method provides a capability for characterising the particles in suspensions. Electrical impedance tomography based on EIS measurement or namely, electrical impedance tomography spectroscopy (EITS) could image the spatial distribution of particle characteristics. In this paper, a new method, including test set-up and data analysis, for characterisation of particles in suspensions are developed through the experimental approach. The experimental results on tomographic imaging of colloidal particles

  9. Electrical impedance tomography spectroscopy method for characterising particles in solid-liquid phase

    SciTech Connect

    Zhao, Yanlin; Wang, Mi; Yao, Jun

    2014-04-11

    Electrical impedance tomography (EIT) is one of the process tomography techniques to provide an on-line non-invasive imaging for multiphase flow measurement. With EIT measurements, the images of impedance real part, impedance imaginary part, phase angle, and magnitude can be obtained. However, most of the applications of EIT in the process industries rely on the conductivity difference between two phases in fluids to obtain the concentration profiles. It is not common to use the imaginary part or phase angle due to the dominant change in conductivity or complication in the use of other impedance information. In a solid-liquid two phases system involving nano- or submicro-particles, characterisation of particles (e.g. particle size and concentration) have to rely on the measurement of impedance phase angle or imaginary part. Particles in a solution usually have an electrical double layer associated with their surfaces and can form an induced electrical dipole moment due to the polarization of the electrical double layer under the influence of an alternating electric field. Similar to EIT, electrical impedance spectroscopy (EIS) measurement can record the electrical impedance data, including impedance real part, imaginary part and phase angle (θ), which are caused by the polarization of the electrical double layer. These impedance data are related to the particle characteristics e.g. particle size, particle and ionic concentrations in the aqueous medium, therefore EIS method provides a capability for characterising the particles in suspensions. Electrical impedance tomography based on EIS measurement or namely, electrical impedance tomography spectroscopy (EITS) could image the spatial distribution of particle characteristics. In this paper, a new method, including test set-up and data analysis, for characterisation of particles in suspensions are developed through the experimental approach. The experimental results on tomographic imaging of colloidal particles

  10. Surveillance of deep vein thrombosis in asymptomatic total hip replacement patients. Impedance phlebography and fibrinogen scanning versus roentgenographic phlebography

    SciTech Connect

    Paiement, G.; Wessinger, S.J.; Waltman, A.C.; Harris, W.H.

    1988-03-01

    Nine hundred thirty-seven limbs in 537 patients over the age of 39 years who underwent total hip replacement were studied by roentgenographic phlebography, cuff-impedance phlebography, and iodine-125 fibrinogen scanning. Cuff-impedance phlebography had a sensitivity of only 12.3 percent for thigh thrombi. Fibrinogen scanning had a sensitivity of only 59.1 percent for calf thrombi and 13.7 percent for thigh thrombi. The combined use of the two methods resulted in only a 23.2 percent sensitivity for thigh thrombi and an overall sensitivity of 47.4 percent. We have concluded that in asymptomatic patients, in contrast with symptomatic patients, the combination of cuff-impedance phlebography and fibrinogen scanning is not an effective screening method.

  11. Noninvasive electrical impedance sensor for in vivo tissue discrimination at radio frequencies.

    PubMed

    Dai, Yu; Du, Jun; Yang, Qing; Zhang, Jianxun

    2014-09-01

    Compared to traditional open surgery, minimally invasive surgery (MIS) allows for a more rapid and less painful recovery. However, the lack of significant haptic feedback in MIS can make tissue discrimination difficult. This paper tests a noninvasive electrical impedance sensor for in vivo discrimination of tissue types in MIS. The sensor consists of two stainless steel spherical electrodes used to measure the impedance spectra over the frequency range of 200 kHz to 5 MHz. The sensor helps ensure free movement on an organ surface and prevents soft tissues from being injured during impedance measurement. Since the recorded electrical impedance is correlated with the force pressed on the electrode and the mechanical property of the tissue, the electrode-tissue contact impedance is calculated theoretically. We show that the standard deviation of the impedance ratio at each frequency point is sufficient to distinguish different tissue types. Both in vitro experiment in a pig kidney and in vivo experiment in rabbit organs were performed to demonstrate the feasibility of the electrical impedance sensor. The experimental results indicated that the sensor, used with the proposed data-processing method, provides accurate and reliable biological tissue discrimination. PMID:24764269

  12. Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators

    PubMed Central

    Kim, Pil-Jong; Kim, Hong-Gee

    2015-01-01

    Objectives The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). Materials and Methods The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC. PMID:25984472

  13. Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics

    PubMed Central

    Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun

    2014-01-01

    When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493

  14. Estimation of electrical conductivity of a layered spherical head model using electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Fernández-Corazza, M.; von-Ellenrieder, N.; Muravchik, C. H.

    2011-12-01

    Electrical Impedance Tomography (EIT) is a non-invasive method that aims to create an electrical conductivity map of a volume. In particular, it can be applied to study the human head. The method consists on the injection of an unperceptive and known current through two electrodes attached to the scalp, and the measurement of the resulting electric potential distribution at an array of sensors also placed on the scalp. In this work, we propose a parametric estimation of the brain, scalp and skull conductivities using EIT over an spherical model of the head. The forward problem involves the computation of the electric potential on the surface, for given the conductivities and the injection electrode positions, while the inverse problem consists on estimating the conductivities given the sensor measurements. In this study, the analytical solution to the forward problem based on a three layer spherical model is first described. Then, some measurements are simulated adding white noise to the solutions and the inverse problem is solved in order to estimate the brain, skull and scalp conductivity relations. This is done with a least squares approach and the Nelder-Mead multidimensional unconstrained nonlinear minimization method.

  15. Electrical Impedance Spectroscopy-Based Defect Sensing Technique in Estimating Cracks

    PubMed Central

    Zhang, Tingting; Zhou, Liangdong; Ammari, Habib; Seo, Jin Keun

    2015-01-01

    A defect sensing method based on electrical impedance spectroscopy is proposed to image cracks and reinforcing bars in concrete structures. The method utilizes the frequency-dependent behavior of thin insulating cracks: low-frequency electrical currents are blocked by insulating cracks, whereas high-frequency currents can pass through thin cracks to probe the conducting bars. From various frequency-dependent electrical impedance tomography (EIT) images, we can show its advantage in terms of detecting both thin cracks with their thickness and bars. We perform numerical simulations and phantom experiments to support the feasibility of the proposed method. PMID:26007713

  16. ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON DURING ACTIVITY.

    PubMed

    Cole, K S; Curtis, H J

    1939-05-20

    Alternating current impedance measurements have been made over a wide frequency range on the giant axon from the stellar nerve of the squid, Loligo pealii, during the passage of a nerve impulse. The transverse impedance was measured between narrow electrodes on either side of the axon with a Wheatstone bridge having an amplifier and cathode ray oscillograph for detector. When the bridge was balanced, the resting axon gave a narrow line on the oscillograph screen as a sweep circuit moved the spot across. As an impulse passed between impedance electrodes after the axon had been stimulated at one end, the oscillograph line first broadened into a band, indicating a bridge unbalance, and then narrowed down to balance during recovery. From measurements made during the passage of the impulse and appropriate analysis, it was found that the membrane phase angle was unchanged, the membrane capacity decreased about 2 per cent, while the membrane conductance fell from a resting value of 1000 ohm cm.(2) to an average of 25 ohm cm.(2) The onset of the resistance change occurs somewhat after the start of the monophasic action potential, but coincides quite closely with the point of inflection on the rising phase, where the membrane current reverses in direction, corresponding to a decrease in the membrane electromotive force. This E.M.F. and the conductance are closely associated properties of the membrane, and their sudden changes constitute, or are due to, the activity which is responsible for the all-or-none law and the initiation and propagation of the nerve impulse. These results correspond to those previously found for Nitella and lead us to expect similar phenomena in other nerve fibers. PMID:19873125

  17. Electrical transport properties of manganese containing pyrochlore type semiconducting oxides using impedance analyses

    SciTech Connect

    Sumi, S.; Prabhakar Rao, P.; Mahesh, S.K.; Koshy, Peter

    2012-12-15

    Graphical abstract: DC conductivity variation of CaCe{sub 1−x}Mn{sub x}SnNbO{sub 7−δ} (x = 0, 0.2, 0.4 and 0.6) with inverse of temperature. Variation of conductivity with Mn concentration at 600 °C is shown in the inset. Display Omitted Highlights: ► We have observed that the structural ordering as well as grain size increase with Mn substitution. ► Impedance analysis proved that a correlated barrier hopping type conduction mechanism is involved in the materials. ► Activation energy as well as electrical conductivity increases with increase in Mn substitution. ► Localization of electrons associated with Mn{sup 2+} and structural ordering are the key factors for the increased activation energy with Mn substitution. ► All the materials showed good NTC thermistor properties. -- Abstract: A new series of manganese containing pyrochlore type semiconducting oxides CaCe{sub 1−x}Mn{sub x}SnNbO{sub 7−δ} (x = 0, 0.2, 0.4 and 0.6) have been synthesized to study the effect of Mn substitution on the structure, microstructure and electrical properties of these samples. X-ray diffraction and scanning electron microscopy studies revealed an increase of structural ordering and grain size respectively with increase of Mn substitution. Rietveld analysis and Raman spectroscopy were also employed to corroborate the XRD results. The bulk resistance measurements with temperature exhibit negative temperature coefficient behavior. The impedance analysis of the samples revealed a non-Debye type relaxation existed in the materials. The ac conductivity variation with temperature and frequency indicates a correlated barrier hopping type conduction mechanism in these materials. The barrier height and the intersite separation for hopping influence the electrical conductivity of these samples and are found to be a function of localization of electrons associated with the Mn{sup 2+} ions and the unit cell volume respectively. The Mn substitution increases both electrical

  18. The use of electrical impedance spectroscopy for monitoring the hydration products of Portland cement mortars with high percentage of pozzolans

    SciTech Connect

    Cruz, J.M.; Fita, I.C.; Soriano, L.; Payá, J.; Borrachero, M.V.

    2013-08-15

    In this paper, mortars and pastes containing large replacement of pozzolan were studied by mechanical strength, thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), mercury intrusion porosimetry (MIP) and electrical impedance spectroscopy (EIS). The effect of metakaolin (35%) and fly ash (60%) was evaluated and compared with an inert mineral addition (andalusite). The portlandite content was measured, finding that the pozzolanic reaction produced cementing systems with all portlandite fixed. The EIS measurements were analyzed by the equivalent electrical circuit (EEC) method. An EEC with three branches in parallel was applied. The dc resistance was related to the degree of hydration and allowed us to characterize plain and blended mortars. A constant phase element (CPE) quantified the electrical properties of the hydration products located in the solid–solution interface and was useful to distinguish the role of inert and pozzolanic admixtures present in the cement matrix.

  19. Spatial feature tracking impedence sensor using multiple electric fields

    DOEpatents

    Novak, J.L.

    1998-08-11

    Linear and other features on a workpiece are tracked by measuring the fields generated between electrodes arrayed in pairs. One electrode in each pair operates as a transmitter and the other as a receiver, and both electrodes in a pair are arrayed on a carrier. By combining and subtracting fields between electrodes in one pair and between a transmitting electrode in one pair and a receiving electrode in another pair, information describing the location and orientation of the sensor relative to the workpiece in up to six degrees of freedom may be obtained. Typical applications will measure capacitance, but other impedance components may be measured as well. The sensor is designed to track a linear feature axis or a protrusion or pocket in a workpiece. Seams and ridges can be tracked by this non-contact sensor. The sensor output is useful for robotic applications. 10 figs.

  20. Spatial feature tracking impedence sensor using multiple electric fields

    DOEpatents

    Novak, James L.

    1998-01-01

    Linear and other features on a workpiece are tracked by measuring the fields generated between electrodes arrayed in pairs. One electrode in each pair operates as a transmitter and the other as a receiver, and both electrodes in a pair are arrayed on a carrier. By combining and subtracting fields between electrodes in one pair and between a transmitting electrode in one pair and a receiving electrode in another pair, information describing the location and orientation of the sensor relative to the workpiece in up to six degrees of freedom may be obtained. Typical applications will measure capacitance, but other impedance components may be measured as well. The sensor is designed to track a linear feature axis or a protrusion or pocket in a workpiece. Seams and ridges can be tracked by this non-contact sensor. The sensor output is useful for robotic applications.

  1. An Analysis of Electrical Impedance Measurements Applied for Plant N Status Estimation in Lettuce (Lactuca sativa)

    PubMed Central

    Muñoz-Huerta, Rafael F.; de J. Ortiz-Melendez, Antonio; Guevara-Gonzalez, Ramon G.; Torres-Pacheco, Irineo; Herrera-Ruiz, Gilberto; Contreras-Medina, Luis M.; Prado-Olivarez, Juan; Ocampo-Velazquez, Rosalia V.

    2014-01-01

    Nitrogen plays a key role in crop yields. Hence, farmers may apply excessive N fertilizers to crop fields, inducing environmental pollution. Crop N monitoring methods have been developed to improve N fertilizer management, most of them based on leaf or canopy optical-property measurements. However, sensitivity to environmental interference remains an important drawback. Electrical impedance has been applied to determine the physiological and nutritional status of plant tissue, but no studies related to plant-N contents are reported. The objective of this article is to analyze how the electrical impedance response of plants is affected by their N status. Four sets of lettuce (Lactuca sativa L.) with a different N-source concentrations per set were used. Total nitrogen and electrical impedance spectra (in a 1 to 100 kHz frequency range) were measured five times per set, three times every other day. Minimum phase angles of impedance spectra were detected and analyzed, together with the frequency value in which they occurred, and their magnitude at that frequency. High and positive correlation was observed between plant N content and frequency values at minimum phase angle with no significant variations detected between days of measurement. These results suggest that electrical impedance can be sensitive to plant N status. PMID:25057134

  2. Flow aeroacoustic damping using coupled mechanical-electrical impedance in lined pipeline

    NASA Astrophysics Data System (ADS)

    Chen, Yong; Huang, Yi-Yong; Chen, Xiao-Qian; Bai, Yu-Zhu; Tan, Xiao-Dong

    2015-05-01

    We report a new noise-damping concept which utilizes a coupled mechanical-electrical acoustic impedance to attenuate an aeroacoustic wave propagating in a moving gas confined by a cylindrical pipeline. An electrical damper is incorporated to the mechanical impedance, either through the piezoelectric, electrostatic, or electro-magnetic principles. Our numerical study shows the advantage of the proposed methodology on wave attenuation. With the development of the micro-electro-mechanical system and material engineering, the proposed configuration may be promising for noise reduction. Project supported by the National Natural Science Foundation of China (Grant Nos. 11404405, 91216201, 51205403, and 11302253).

  3. Measuring the multi-frequency electrical impedance of the mouse gastrocnemius muscle using a tetrapolar technique

    NASA Astrophysics Data System (ADS)

    Li, J.; Fogerson, P. M.; Rutkove, S. B.

    2010-04-01

    Electrical impedance methods can be used to evaluate and monitor neuromuscular disease states. Recently, we have applied tetrapolar surface electrical impedance methods to the gastrocnemius muscle of the rat for this purpose and substantial changes in the impedance parameters after sciatic nerve crush can be identified. In order to be able to study additional animal models of nerve and muscle disease, however, it would highly desirable to be able to perform such impedance measurements in the mouse. Yet the small size of the mouse presents a substantial technical challenge. In this study, we evaluate a basic approach for performing such measurements. A series of thin, stainless steel strip electrodes affixed to the gastrocnemius and interfaced via a separate connector to the Imp SFB7® (Impedimed, Inc), provided an effective means for obtaining impedance data in the 20-500 kHz range. After two weeks, test-retest reproducibility was good, with intra-class correlation coefficients as high 0.84 and variability as low as 12.86 ± 6.18% in the 15 mice studied. Using this approach, it may now be possible to study impedance changes in a variety of mouse models of neuromuscular disease, including amyotrophic lateral sclerosis, spinal muscular atrophy, muscular dystrophy and Charcot-Marie-Tooth disease.

  4. Determination of salt content in various depth of pork chop by electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Kaltenecker, P.; Szöllösi, D.; Friedrich, L.; Vozáry, E.

    2013-04-01

    The salt concentration was determined inside of pork chop both by electrical impedance spectroscopy and by a conventional chemical method (according to Mohr). The pork chop in various depths (4 mm, 10 mm, 20 mm and 25 mm) was punctured with two stainless steel electrodes. The length of electrodes was 60 mm, and they were insulated along the length except 1 cm section on the end, so the measurement of impedance was realized in various depths. The magnitude and phase angle of impedance were measured with a HP 4284A and a HP 4285A LCR meters from 30 Hz up to 1 MHz and from 75 kHz up to 30 MHz frequency range, respectively at 1 V voltage. The distance between the electrodes was 1 cm. The impedance magnitude decreased as the salt concentration increased. The magnitude of open-short corrected impedance values at various frequencies (10 kHz, 100 kHz, 125 kHz, 1.1 MHz and 8 MHz) showed a good correlation with salt content determined by chemical procedure. The electrical impedance spectroscopy seems a prospective method for determination the salt concentration inside the meat in various depths during the curing procedure.

  5. Using of electrical impedance tomography for diagnostics of the cervix uteri diseases

    NASA Astrophysics Data System (ADS)

    Trokhanova, O. V.; Chijova, Y. A.; Okhapkin, M. B.; Korjenevsky, A. V.; Tuykin, T. S.

    2010-04-01

    The report presents results of investigation of the neck of the womb (cervix) of 64 women aged from 19 to 70, that formed 4 clinical groups (1st group: 15 women without any pathology of the cervix, 2nd group: 27 women with the erosion, 3rd group: 11 women with dysplasia, 4th group: 11 women with cancer of the cervix). The aim of this research is to assess the capabilities of electrical impedance tomography in the diagnostics of the cervix diseases. The methods of the research were: visual examination with the speculum, colposcopy, and biopsy of the cervix. Also the new method of visualization of the cervix was used - electrical impedance tomography with the help of gynecological impedance tomograph (GIT). The following results were obtained. The electrical conductivity of the cervix in norm and in different pathology has different indices, which allow differential diagnostics of benign and malignant diseases. Summary: the method of electrical impedance tomography allows not only visually estimate portio vaginalis, but receive indices of electrical conductivity of the cervix on the depth up to 0.8 cm and thereby reveal pathological changes in epithelium without invasive and operative intervention.

  6. New equivalent-electrical circuit model and a practical measurement method for human body impedance.

    PubMed

    Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako

    2015-01-01

    Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance. PMID:26406074

  7. Effect of Electrode Belt and Body Positions on Regional Pulmonary Ventilation- and Perfusion-Related Impedance Changes Measured by Electric Impedance Tomography

    PubMed Central

    Ericsson, Elin; Tesselaar, Erik; Sjöberg, Folke

    2016-01-01

    Ventilator-induced or ventilator-associated lung injury (VILI/VALI) is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT) can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion. PMID:27253433

  8. Effect of Electrode Belt and Body Positions on Regional Pulmonary Ventilation- and Perfusion-Related Impedance Changes Measured by Electric Impedance Tomography.

    PubMed

    Ericsson, Elin; Tesselaar, Erik; Sjöberg, Folke

    2016-01-01

    Ventilator-induced or ventilator-associated lung injury (VILI/VALI) is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT) can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion. PMID:27253433

  9. A Review of Electrical Impedance Spectrometry Methods for Parametric Estimation of Physiologic Fluid Volumes

    NASA Technical Reports Server (NTRS)

    Dewberry, B.

    2000-01-01

    Electrical impedance spectrometry involves measurement of the complex resistance of a load at multiple frequencies. With this information in the form of impedance magnitude and phase, or resistance and reactance, basic structure or function of the load can be estimated. The "load" targeted for measurement and estimation in this study consisted of the water-bearing tissues of the human calf. It was proposed and verified that by measuring the electrical impedance of the human calf and fitting this data to a model of fluid compartments, the lumped-model volume of intracellular and extracellular spaces could be estimated, By performing this estimation over time, the volume dynamics during application of stimuli which affect the direction of gravity can be viewed. The resulting data can form a basis for further modeling and verification of cardiovascular and compartmental modeling of fluid reactions to microgravity as well as countermeasures to the headward shift of fluid during head-down tilt or spaceflight.

  10. On-line monitoring of the crystallization process: relationship between crystal size and electrical impedance spectra

    NASA Astrophysics Data System (ADS)

    Zhao, Yanlin; Yao, Jun; Wang, Mi

    2016-07-01

    On-line monitoring of crystal size in the crystallization process is crucial to many pharmaceutical and fine-chemical industrial applications. In this paper, a novel method is proposed for the on-line monitoring of the cooling crystallization process of L-glutamic acid (LGA) using electrical impedance spectroscopy (EIS). The EIS method can be used to monitor the growth of crystal particles relying on the presence of an electrical double layer on the charged particle surface and the polarization of double layer under the excitation of alternating electrical field. The electrical impedance spectra and crystal size were measured on-line simultaneously by an impedance analyzer and focused beam reflectance measurement (FBRM), respectively. The impedance spectra were analyzed using the equivalent circuit model and the equivalent circuit elements in the model can be obtained by fitting the experimental data. Two equivalent circuit elements, including capacitance (C 2) and resistance (R 2) from the dielectric polarization of the LGA solution and crystal particle/solution interface, are in relation with the crystal size. The mathematical relationship between the crystal size and the equivalent circuit elements can be obtained by a non-linear fitting method. The function can be used to predict the change of crystal size during the crystallization process.

  11. Interpulse multifrequency electrical impedance measurements during electroporation of adherent differentiated myotubes.

    PubMed

    García-Sánchez, Tomás; Azan, Antoine; Leray, Isabelle; Rosell-Ferrer, Javier; Bragós, Ramon; Mir, Lluis M

    2015-10-01

    In this study, electrical impedance spectroscopy measurements are performed during electroporation of monolayers of differentiated myotubes. The time resolution of the system (1 spectrum/ms) enable 860 full spectra (21 frequencies from 5 kHz to 1.3 MHz) to be acquired during the time gap between consecutive pulses (interpulse) of a classical electroporation treatment (8 pulses, 100 μs, 1 Hz). Additionally, the characteristics of the custom microelectrode assembly used allow the experiments to be performed directly in situ in standard 24 multi-well plates. The impedance response dynamics are studied for three different electric field intensities (400, 800 and 1200 V/cm). The multifrequency information, analysed with the Cole model, reveals a short-term impedance recovery after each pulse in accordance with the fast resealing of the cell membrane, and a long-term impedance decay over the complete treatment in accordance with an accumulated effect pulse after pulse. The analysis shows differences between the lowest electric field condition and the other two, suggesting that different mechanisms that may be related with the reversibility of the process are activated. As a result of the multifrequency information, the system is able to measure simultaneously the conductivity variations due to ion diffusion during electroporation. Finally, in order to reinforce the physical interpretation of the results, a complementary electrical equivalent model is used. PMID:26123676

  12. Development of an Anatomically Realistic Forward Solver for Thoracic Electrical Impedance Tomography

    PubMed Central

    Yang, Fei; Zhang, Jie; Patterson, Robert

    2013-01-01

    Electrical impedance tomography (EIT) has the potential to provide a low cost and safe imaging modality for clinically monitoring patients being treated with mechanical ventilation. Variations in reconstruction algorithms at different clinical settings, however, make interpretation of regional ventilation across institutions difficult, presenting the need for a unified algorithm for thoracic EIT reconstruction. Development of such a consensual reconstruction algorithm necessitates a forward model capable of predicting surface impedance measurements as well as electric fields in the interior of the modeled thoracic volume. In this paper, we present an anatomically realistic forward solver for thoracic EIT that was built based on high resolution MR image data of a representative adult. Accuracy assessment of the developed forward solver in predicting surface impedance measurements by comparing the predicted and observed impedance measurements shows that the relative error is within the order of 5%, demonstrating the ability of the presented forward solver in generating high-fidelity surface thoracic impedance data for thoracic EIT algorithm development and evaluation. PMID:27006927

  13. Relationship between moisture content and electrical impedance of carrot slices during drying

    NASA Astrophysics Data System (ADS)

    Kertész, Ákos; Hlaváčová, Zuzana; Vozáry, Eszter; Staroňová, Lenka

    2015-01-01

    Electrical properties of food materials can give information about the inner structure and physiological state of biological tissues. Generally, the process of drying of fruits and vegetables is followed by weight loss. The aim of this study was to measure the impedance spectra of carrot slices during drying and to correlate impedance parameters to moisture content in different drying periods. Cylindrical slices were cut out from the carrot root along the axis. The slices were dried in a Venticell 111 air oven at 50°C. The weight of the slices was measured with a Denver SI-603 electronic analytical and precision balance. The weighing of the samples was performed every 30 min at the beginning of drying and every 60 min after the process. The moisture content of the samples was calculated on wet basis. The magnitude and phase angle of electrical impedance of the slices were measured with HP 4284A and 4285A precision LCR meters in the frequency range from 30 Hz to 1 MHz and from 75 kHz to 30 MHz, respectively, at voltage 1 V. The impedance measurement was performed after weighting. The change in the magnitude of impedance during drying showed a good correlation with the change in the moisture content.

  14. Skin impedance is not a factor in transcutaneous electrical nerve stimulation effectiveness

    PubMed Central

    Vance, Carol GT; Rakel, Barbara A; Dailey, Dana L; Sluka, Kathleen A

    2015-01-01

    Objective Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological intervention used to manage pain using skin surface electrodes. Optimal electrode placement is unclear. We hypothesized that better analgesia would occur if electrodes were placed over sites with lower skin impedance. Optimal site selection (OSS) and sham site selection (SSS) electrode sites on the forearm were identified using a standard clinical technique. Methods Experiment 1 measured skin impedance in the forearm at OSS and SSS. Experiment 2 was a crossover design double-blind randomized controlled trial comparing OSS-TENS, SSS-TENS, and placebo TENS (P-TENS) to confirm differences in skin impedance between OSS and SSS, and measure change in pressure pain threshold (PPT) following a 30-minute TENS treatment. Healthy volunteers were recruited (ten for Experiment 1 [five male, five female] and 24 for Experiment 2 [12 male, 12 female]). TENS was applied for 30 minutes at 100 Hz frequency, 100 µs pulse duration, and “strong but nonpainful” amplitude. Results Experiment 1 results demonstrate significantly higher impedance at SSS (17.69±1.24 Ω) compared to OSS (13.53±0.57 Ω) (P=0.007). For Experiment 2, electrode site impedance was significantly higher over SSS, with both the impedance meter (P=0.001) and the TENS unit (P=0.012) compared to OSS. PPT change was significantly greater for both OSS-TENS (P=0.024) and SSS-TENS (P=0.025) when compared to P-TENS. PPT did not differ between the two active TENS treatments (P=0.81). Conclusion Skin impedance is lower at sites characterized as optimal using the described technique of electrode site selection. When TENS is applied at adequate intensities, skin impedance is not a factor in attainment of hypoalgesia of the forearm in healthy subjects. Further investigation should include testing in patients presenting with painful conditions. PMID:26316808

  15. Electrical impedance imaging in two-phase, gas-liquid flows: 1. Initial investigation

    NASA Technical Reports Server (NTRS)

    Lin, J. T.; Ovacik, L.; Jones, O. C.

    1991-01-01

    The determination of interfacial area density in two-phase, gas-liquid flows is one of the major elements impeding significant development of predictive tools based on the two-fluid model. Currently, these models require coupling of liquid and vapor at interfaces using constitutive equations which do not exist in any but the most rudimentary form. Work described herein represents the first step towards the development of Electrical Impedance Computed Tomography (EICT) for nonintrusive determination of interfacial structure and evolution in such flows.

  16. Study the effects of moisture content on the electrical properties of technical textiles by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lusis, A.; Pentjuss, E.; Bajars, G.; Gabrusenoks, J.; Janeliukštis, R.; Zandersons, J.

    2012-08-01

    Application of metal coatings for the functionalization of technical fibres and fabrics faced with influence of moisture on functional properties, e.g., the impedance of the metal coated K-glass fabrics have strong dependence of content absorbed water or moisture. The paper devoted to develop methodology for characterisation functional materials based on fabrics and model for interpretation of the electrical impedance spectra to obtained functional characteristics of technical textile fabrics. Model based on analyses of 3D plot of imaginary part of complex modulus spectra versus sample mass. Methodology helps to control content of adsorbed water in fabric and influence of moisture on the functional characteristics.

  17. Dynamic Impedance Model of the Skin-Electrode Interface for Transcutaneous Electrical Stimulation

    PubMed Central

    Vargas Luna, José Luis; Krenn, Matthias; Cortés Ramírez, Jorge Armando; Mayr, Winfried

    2015-01-01

    Transcutaneous electrical stimulation can depolarize nerve or muscle cells applying impulses through electrodes attached on the skin. For these applications, the electrode-skin impedance is an important factor which influences effectiveness. Various models describe the interface using constant or current-depending resistive-capacitive equivalent circuit. Here, we develop a dynamic impedance model valid for a wide range stimulation intensities. The model considers electroporation and charge-dependent effects to describe the impedance variation, which allows to describe high-charge pulses. The parameters were adjusted based on rectangular, biphasic stimulation pulses generated by a stimulator, providing optionally current or voltage-controlled impulses, and applied through electrodes of different sizes. Both control methods deliver a different electrical field to the tissue, which is constant throughout the impulse duration for current-controlled mode or have a very current peak for voltage-controlled. The results show a predominant dependence in the current intensity in the case of both stimulation techniques that allows to keep a simple model. A verification simulation using the proposed dynamic model shows coefficient of determination of around 0.99 in both stimulation types. The presented method for fitting electrode-skin impedance can be simple extended to other stimulation waveforms and electrode configuration. Therefore, it can be embedded in optimization algorithms for designing electrical stimulation applications even for pulses with high charges and high current spikes. PMID:25942010

  18. Lorentz force electrical impedance tomography using magnetic field measurements

    NASA Astrophysics Data System (ADS)

    Zengin, Reyhan; Güneri Gençer, Nevzat

    2016-08-01

    In this study, magnetic field measurement technique is investigated to image the electrical conductivity properties of biological tissues using Lorentz forces. This technique is based on electrical current induction using ultrasound together with an applied static magnetic field. The magnetic field intensity generated due to induced currents is measured using two coil configurations, namely, a rectangular loop coil and a novel xy coil pair. A time-varying voltage is picked-up and recorded while the acoustic wave propagates along its path. The forward problem of this imaging modality is defined as calculation of the pick-up voltages due to a given acoustic excitation and known body properties. Firstly, the feasibility of the proposed technique is investigated analytically. The basic field equations governing the behaviour of time-varying electromagnetic fields are presented. Secondly, the general formulation of the partial differential equations for the scalar and magnetic vector potentials are derived. To investigate the feasibility of this technique, numerical studies are conducted using a finite element method based software. To sense the pick-up voltages a novel coil configuration (xy coil pairs) is proposed. Two-dimensional numerical geometry with a 16-element linear phased array (LPA) ultrasonic transducer (1 MHz) and a conductive body (breast fat) with five tumorous tissues is modeled. The static magnetic field is assumed to be 4 Tesla. To understand the performance of the imaging system, the sensitivity matrix is analyzed. The sensitivity matrix is obtained for two different locations of LPA transducer with eleven steering angles from -{{25}\\circ} to {{25}\\circ} at intervals of {{5}\\circ} . The characteristics of the imaging system are shown with the singular value decomposition (SVD) of the sensitivity matrix. The images are reconstructed with the truncated SVD algorithm. The signal-to-noise ratio in measurements is assumed 80 dB. Simulation studies

  19. Lorentz force electrical impedance tomography using magnetic field measurements.

    PubMed

    Zengin, Reyhan; Gençer, Nevzat Güneri

    2016-08-21

    In this study, magnetic field measurement technique is investigated to image the electrical conductivity properties of biological tissues using Lorentz forces. This technique is based on electrical current induction using ultrasound together with an applied static magnetic field. The magnetic field intensity generated due to induced currents is measured using two coil configurations, namely, a rectangular loop coil and a novel xy coil pair. A time-varying voltage is picked-up and recorded while the acoustic wave propagates along its path. The forward problem of this imaging modality is defined as calculation of the pick-up voltages due to a given acoustic excitation and known body properties. Firstly, the feasibility of the proposed technique is investigated analytically. The basic field equations governing the behaviour of time-varying electromagnetic fields are presented. Secondly, the general formulation of the partial differential equations for the scalar and magnetic vector potentials are derived. To investigate the feasibility of this technique, numerical studies are conducted using a finite element method based software. To sense the pick-up voltages a novel coil configuration (xy coil pairs) is proposed. Two-dimensional numerical geometry with a 16-element linear phased array (LPA) ultrasonic transducer (1 MHz) and a conductive body (breast fat) with five tumorous tissues is modeled. The static magnetic field is assumed to be 4 Tesla. To understand the performance of the imaging system, the sensitivity matrix is analyzed. The sensitivity matrix is obtained for two different locations of LPA transducer with eleven steering angles from [Formula: see text] to [Formula: see text] at intervals of [Formula: see text]. The characteristics of the imaging system are shown with the singular value decomposition (SVD) of the sensitivity matrix. The images are reconstructed with the truncated SVD algorithm. The signal-to-noise ratio in measurements is assumed 80 d

  20. A shape decomposition technique in electrical impedance tomography

    SciTech Connect

    Han, D.K.; Prosperetti, A.

    1999-10-10

    Consider a two-dimensional domain containing a medium with unit electrical conductivity and one or more non-conducting objects. The problem considered here is that of identifying shape and position of the objects on the sole basis of measurements on the external boundary of the domain. An iterative technique is presented in which a sequence of solutions of the direct problem is generated by a boundary element method on the basis of assumed positions and shapes of the objects. The key new aspect of the approach is that the boundary of each object is represented in terms of Fourier coefficients rather than a point-wise discretization. These Fourier coefficients generate the fundamental shapes mentioned in the title in terms of which the object shape is decomposed. The iterative procedure consists in the successive updating of the Fourier coefficients at every step by means of the Levenberg-Marquardt algorithm. It is shown that the Fourier decomposition--which, essentially, amounts to a form of image compression--enables the algorithm to image the embedded objects with unprecedented accuracy and clarity. In a separate paper, the method has also been extended to three dimensions with equally good results.

  1. Use of low-frequency electrical impedance measurements to determine phospholipid content in amniotic fluid

    NASA Astrophysics Data System (ADS)

    DeLuca, F.; Cametti, C.; Zimatore, G.; Maraviglia, B.; Pachi', A.

    1996-09-01

    In this report we propose a new method for an in vitro test of the foetal lung maturity based on the measurement of the electrical conductivity of the overall amniotic fluid obtained from transabdominal amniocentesis, since this quantity can be linked to a first approximation in a very simple way to the phospholipid content. We have carried out measurements of 85 different samples of amniotic fluid as a function of gestation weeks and we have observed a pronounced change of the electrical conductivity that reflects the increase in the phospholipid concentration occurring at the end of normal pregnancies. The method could be further developed to obtain similar information on in vivo experiments by means of bioelectric impedance tomography, taking advantage of the frequency dependence of the tissue electrical impedance.

  2. Noninvasive Imaging of Head-Brain Conductivity Profiles Using Magnetic Resonance Electrical Impedance Imaging

    PubMed Central

    Zhang, Xiaotong; Yan, Dandan; Zhu, Shanan; He, Bin

    2008-01-01

    Magnetic resonance electrical impedance tomography (MREIT) is a recently introduced non-invasive conductivity imaging modality, which combines the magnetic resonance current density imaging (CDI) and the traditional electrical impedance tomography (EIT) techniques. MREIT is aimed at providing high spatial resolution images of electrical conductivity, by avoiding solving the well-known ill-posed problem in the traditional EIT. In this paper, we review our research activities in MREIT imaging of head-brain tissue conductivity profiles. We have developed several imaging algorithms and conducted a series of computer simulations for MREIT imaging of the head and brain tissues. Our work suggests MREIT brain imaging may become a useful tool in imaging conductivity distributions of the brain and head. PMID:18799394

  3. Electrically scanning microwave radiometer for Nimbus E

    NASA Technical Reports Server (NTRS)

    1973-01-01

    An electronically scanning microwave radiometer system has been designed, developed, and tested for measurement of meteorological, geomorphological and oceanographic parameters from NASA/GSFC's Nimbus E satellite. The system is a completely integrated radiometer designed to measure the microwave brightness temperature of the earth and its atmosphere at a microwave frequency of 19.35 GHz. Calibration and environmental testing of the system have successfully demonstrated its ability to perform accurate measurements in a satellite environment. The successful launch and data acquisition of the Nimbus 5 (formerly Nimbus E) gives further demonstration to its achievement.

  4. Feasibility studies of electrical impedance spectroscopy for monitoring tissue response to photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Wilson, Brian C.; Osterman, Kendra S.; Hoopes, P. Jack; Lilge, Lothar D.; Paulsen, Keith D.

    1998-05-01

    Electrical impedance spectroscopy (EIS) has been evaluated as a non- or minimally-invasive technique to monitor the acute tissue response to photodynamic therapy (PDT). In this study the EIS spectra of normal muscle tissue in the rat hind leg were monitored immediately before and at time intervals up to 96 hours post-PDT treatment with different photosensitizers (Photofrin, ALA-induced PpIX, BenzoPorphyrin Derivative), at varying photosensitizer and light doses. EIS measurements were made using a pair of solid matrix Ag-AgCl electrodes placed parallel to one another on either side of the muscle mass and interfaced to a precision LCR impedance meter scanning the frequency range 1 - 1000 KHz. Independent histological grading of tissue injury was performed on tissue sections from treated and untreated legs at the 96 hour end point. Significant and PDT dose-dependent changes in the EIS spectra following treatment were observed, including increases in conductivity which correlated with the immediate post-PDT edematous response with Photofrin and ALA and which resolved or partially-resolved over the measurement time course. Photofrin treatments exhibited a clear drug dose response at 96 hours that was evident in both the EIS spectra and the histological sections. These changes included significant tissue necrosis as well as edema, inflammation and early fibroplasia. The BPD data were less clear, but potentially quite interesting. Most striking were below unity ratios of treated-to-untreated muscle spectra components at 24 hours which reversed to above unity by 96 hours in the through skin measurements. This phenomenon is indicative of a tissue response distinctly different than that observed with Photofrin or ALA. These data also suggest that EIS measured changes are sensitive enough to detect differences in PDT-initiated tissue damage that may be photosensitize-specific. While the data are derived from a small number of animals, the findings are quite encouraging in

  5. Application of stochastic Galerkin FEM to the complete electrode model of electrical impedance tomography

    SciTech Connect

    Leinonen, Matti Hakula, Harri Hyvönen, Nuutti

    2014-07-15

    The aim of electrical impedance tomography is to determine the internal conductivity distribution of some physical body from boundary measurements of current and voltage. The most accurate forward model for impedance tomography is the complete electrode model, which consists of the conductivity equation coupled with boundary conditions that take into account the electrode shapes and the contact resistances at the corresponding interfaces. If the reconstruction task of impedance tomography is recast as a Bayesian inference problem, it is essential to be able to solve the complete electrode model forward problem with the conductivity and the contact resistances treated as a random field and random variables, respectively. In this work, we apply a stochastic Galerkin finite element method to the ensuing elliptic stochastic boundary value problem and compare the results with Monte Carlo simulations.

  6. Physics of a novel magnetic resonance and electrical impedance combination for breast cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Kallergi, Maria; Heine, John J.; Wollin, Ernest

    2015-03-01

    A new technique is proposed and experimentally validated for breast cancer detection and diagnosis. The technique combines magnetic resonance with electrical impedance measurements and has the potential to increase the specificity of magnetic resonance mammography (MRM) thereby reducing false positive biopsy rates. The new magnetic resonance electrical impedance mammography (MREIM) adds a time varying electric field during a supplementary sequence to a standard MRM examination with an apparatus that is "invisible" to the patient. The applied electric field produces a current that creates an additional magnetic field with a component aligned with the bore magnetic field that can alter the native signal in areas of higher electrical conductivity. The justification for adding the electric field is that the electrical conductivity of cancerous breast tissue is approximately 3-40 times higher than normal breast tissue and, hence, conductivity of malignant tissue represents a known clinical disease biomarker. In a pilot study with custom-made phantoms and experimental protocols, it was demonstrated that MREIM can produce, as theoretically predicted, a detectable differential signal in areas of higher electrical conductivity (tumor surrogate regions); the evidence indicates that the differential signal is produced by the confluence of two different effects at full image resolution without gadolinium chelate contrast agent injection, without extraneous reconstruction techniques, and without cumbersome multi-positioned patient electrode configurations. This paper describes the theoretical model that predicts and explains the observed experimental results that were also confirmed by simulation studies.

  7. An in vitro model for investigating impedance changes with cell growth and electrical stimulation: implications for cochlear implants

    NASA Astrophysics Data System (ADS)

    Newbold, Carrie; Richardson, Rachael; Huang, Christie Q.; Milojevic, Dusan; Cowan, Robert; Shepherd, Robert

    2004-12-01

    The impedance of stimulating electrodes used in cochlear implants and other neural prostheses often increases post-implantation, and is thought to be due to fibrous tissue encapsulation of the electrode array. Increased impedance results in higher power requirements to stimulate target neurons at set charge densities. We developed an in vitro model to investigate the electrode-tissue interface in a highly controlled environment. This model was tested using three cell types, with and without charge-balanced biphasic electrical stimulation. Under standard tissue culture conditions, a monolayer of cells was grown over the electrode surface. Electrode impedance increased in proportion to the extent of cell coverage of the electrode. Cell type was a significant factor in the amount of impedance increase, with kidney epithelial cells (MDCK) creating the greatest impedance, followed by dissociated rat skin fibroblasts and then macrophages (J774). The application of electrical stimulation to cell-covered electrodes caused impedance fluctuations similar to that seen in vivo, with a lowering of impedance immediately following stimulation, and a recovery to pre-stimulation levels during inactive periods. Examination of these electrodes suggests that the stimulation-induced impedance changes were due to the amount of cell cover over the electrodes. This in vitro technique accurately models the changes in impedance observed with neural prostheses in vivo, and shows the close relationship between impedance and tissue coverage adjacent to the electrode surface. We believe that this in vitro approach holds great promise to further our knowledge of the mechanisms contributing to electrode impedance.

  8. Regional lung function determined by electrical impedance tomography during bronchodilator reversibility testing in patients with asthma.

    PubMed

    Frerichs, I; Zhao, Z; Becher, T; Zabel, P; Weiler, N; Vogt, B

    2016-06-01

    The measurement of rapid regional lung volume changes by electrical impedance tomography (EIT) could determine regional lung function in patients with obstructive lung diseases during pulmonary function testing (PFT). EIT examinations carried out before and after bronchodilator reversibility testing could detect the presence of spatial and temporal ventilation heterogeneities and analyse their changes in response to inhaled bronchodilator on the regional level. We examined seven patients suffering from chronic asthma (49  ±  19 years, mean age  ±  SD) using EIT at a scan rate of 33 images s(-1) during tidal breathing and PFT with forced full expiration. The patients were studied before and 5, 10 and 20 min after bronchodilator inhalation. Seven age- and sex-matched human subjects with no lung disease history served as a control study group. The spatial heterogeneity of lung function measures was quantified by the global inhomogeneity indices calculated from the pixel values of tidal volume, forced expiratory volume in one second (FEV1), forced vital capacity (FVC), peak flow and forced expiratory flow between 25% and 75% of FVC as well as histograms of pixel FEV1/FVC values. Temporal heterogeneity was assessed using the pixel values of expiration times needed to exhale 75% and 90% of pixel FVC. Regional lung function was more homogeneous in the healthy subjects than in the patients with asthma. Spatial and temporal ventilation distribution improved in the patients with asthma after the bronchodilator administration as evidenced mainly by the histograms of pixel FEV1/FVC values and pixel expiration times. The examination of regional lung function using EIT enables the assessment of spatial and temporal heterogeneity of ventilation distribution during bronchodilator reversibility testing. EIT may become a new tool in PFT, allowing the estimation of the natural disease progression and therapy effects on the regional and not only global level. PMID

  9. The peculiar electrical response of liquid crystal-carbon nanotube systems as seen by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    García-García, A.; Vergaz, R.; Algorri, J. F.; Geday, M. A.; Otón, J. M.

    2015-09-01

    Conductive nanoparticles, especially elongated ones such as carbon nanotubes, dramatically modify the electrical behavior of liquid crystal cells. These nanoparticles are known to reorient with liquid crystals in electric fields, causing significant variations of conductivity at minute concentrations of tens or hundreds ppm. The above notwithstanding, impedance spectroscopy of doped cells in the frequency range customarily employed by liquid crystal devices, 100 Hz-10 kHz, shows a relatively simple resistor/capacitor response where the components of the cell can be univocally assigned to single components of the electrical equivalent circuit. However, widening the frequency range up to 1 MHz or beyond reveals a complex behavior that cannot be explained with the same simple EEC. Moreover, the system impedance varies with the application of electric fields, their effect remaining after removing the field. Carbon nanotubes are reoriented together with liquid crystal reorientation when applying voltage, but barely reoriented back upon liquid crystal relaxation once the voltage is removed. Results demonstrate a remarkable variation in the impedance of the dielectric blend formed by liquid crystal and carbon nanotubes, the irreversible orientation of the carbon nanotubes and possible permanent contacts between electrodes.

  10. Magnetic resonance electrical impedance tomography (MREIT): conductivity and current density imaging

    NASA Astrophysics Data System (ADS)

    Seo, Jin Keun; Kwon, Ohin; Woo, Eung Je

    2005-01-01

    This paper reviews the latest impedance imaging technique called Magnetic Resonance Electrical Impedance Tomography (MREIT) providing information on electrical conductivity and current density distributions inside an electrically conducting domain such as the human body. The motivation for this research is explained by discussing conductivity changes related with physiological and pathological events, electromagnetic source imaging and electromagnetic stimulations. We briefly summarize the related technique of Electrical Impedance Tomography (EIT) that deals with cross-sectional image reconstructions of conductivity distributions from boundary measurements of current-voltage data. Noting that EIT suffers from the ill-posed nature of the corresponding inverse problem, we introduce MREIT as a new conductivity imaging modality providing images with better spatial resolution and accuracy. MREIT utilizes internal information on the induced magnetic field in addition to the boundary current-voltage measurements to produce three-dimensional images of conductivity and current density distributions. Mathematical theory, algorithms, and experimental methods of current MREIT research are described. With numerous potential applications in mind, future research directions in MREIT are proposed.

  11. A Chicken Tissue Phantom for Studying an Electrical Impedance Tomography (EIT) System Suitable for Clinical Imaging

    NASA Astrophysics Data System (ADS)

    Bera, Tushar Kanti; Nagaraju, J.

    2011-12-01

    The study of practical phantoms is essential for assessing the reconstruction algorithms and instrumentation used in Electrical Impedance Tomography (EIT). Responses of saline phantoms with insulator inhomogeneities differ from the real tissue phantoms in several aspects. Also, it is difficult to reconstruct the actual resistivity of the insulator inhomogeneity in a saline background because of their large resistivity difference. A practical biological phantom consisting of two different materials with low resistivity difference is more suitable for impedance imaging studies. In order to demonstrate this, a chicken tissue phantom was developed to study the resistivity imaging in EIT. A 16-electrode array was placed inside the phantom tank filled with chicken muscle tissue paste and chicken tissue. A 1 mA, 50 kHz sinusoidal current was injected at the phantom boundary and the boundary potentials are measured using opposite current injection protocol. Resistivity images were reconstructed from the boundary data using Electrical Impedance and Diffuse Optical Reconstruction Software (EIDORS) and the reconstruction was evaluated by calculating the contrast parameters of the images. Results show that the resistivity of the chicken fat is successfully reconstructed with a proper background resistivity. Impedance spectroscopic studies show that the chicken tissue phantom can be suitably used to evaluate a multifrequency EIT system.

  12. Traveling-wave electrokinetic micropumps: velocity, electrical current, and impedance measurements.

    PubMed

    García-Sánchez, P; Ramos, A; Green, N G; Morgan, H

    2008-09-01

    An array of microelectrodes covered in an electrolyte and energized by a traveling-wave potential produces net movement of the fluid. Arrays of platinum microelectrodes of two different characteristic sizes have been studied. For both sizes of arrays, at low voltages (<2 V pp) the electrolyte flow is in qualitative agreement with the linear theory of ac electroosmosis. At voltages above a threshold, the direction of fluid flow is reversed. The electrical impedance of the electrode-electrolyte system was measured after the experiments, and changes in the electrical properties of the electrolyte were observed. Measurements of the electrical current during pumping of the electrolyte are also reported. Transient behaviors in both electrical current and fluid velocity were observed. The Faradaic currents probably generate conductivity gradients in the liquid bulk, which in turn give rise to electrical forces. These effects are discussed in relation to the fluid flow observations. PMID:18672919

  13. The Amplitude Phase Decomposition for the Magnetotelluric Impedance Tensor and Galvanic Electric Distortion

    NASA Astrophysics Data System (ADS)

    Neukirch, Maik; Rudolf, Daniel; Garcia, Xavier

    2016-04-01

    The introduction of the phase tensor marked a major breakthrough in understanding of, analysing of and dealing with galvanic distortion of the electric field in the Magnetotelluric method. The phase tensor itself can be used for (distortion free) dimensionality analysis, if applicable distortion analysis and even to invert for subsurface models. However, impedance amplitude information is not stored in the phase tensor, therefore the impedance corrected by distortion analysis (or alternative remedies) may yield better results. We formulate an impedance tensor decomposition into the known phase tensor and an amplitude tensor that is shown to be complementary and independent of the phase tensor. The rotational invariant amplitude tensor contains galvanic and inductive amplitudes of which the latter are physically related to the inductive phase information present in the phase tensor. We show, that for the special cases of 1D and 2D subsurfaces, the geometric amplitude tensor parameter (strike and skew) converge to phase tensor parameter and the singular values are the amplitudes of the impedance in TE and TM mode. Further, the physical similarity between inductive phase and amplitude is used to approximate the galvanic amplitude for the general subsurface, which leads to the qualitative interpretation of 3D galvanic distortion: (i) the (purely) galvanic part of the subsurface (as sensed at a given period) may have a changing impact on the impedance (over a period range) and (ii) only the purely galvanic response of the lowest available period should be termed galvanic distortion. The approximation of the galvanic amplitude (and therewith galvanic distortion), though not accurate, offers a new perspective on galvanic distortion, which breaks with the general belief of the need to assume 1D or 2D regional structure for the impedance. The amplitude tensor itself is complementary to the phase tensor containing integrated (galvanic and inductive) subsurface information

  14. Carbon nanotube composites multi-sensing characteristics based on electrical impedance properties.

    PubMed

    Kang, Inpil; Schulz, Mark J; Choi, Yeon-Sun; Hwang, Sung-Ho

    2009-12-01

    CNT composites demonstrate sensory materials properties such as piezoresistivity, chemical and bio selectivity and they can detect structural deterioration, chemical contamination and bio signal by means of their impedance measurement (resistance and capacitance). In this study, electrical impedance characteristics of CNT composite electrodes are studied to simultaneously detect mechanical and chemical symptoms in engineering applications. We measured variations of electrical resistance and capacitance values of CNT composite electrodes under static load for mechanical sensing behavior and under the change of buffer solution amount for chemical sensing behavior. At the mechanical sensing behavior test, the resistance values changed quite linearly under bending and compression loads while the capacitance value varied within small range with invalid relationship to the loads. At the chemical sensing behavior investigation, the electrode's capacitance showed drastic change while the resistance value only changed within few percent range. The independently changing pattern of electrical impedance parameters according to mechanical strain and chemical effect can provide new opportunities to design a novel multifunctional sensor that can simultaneously monitor mechanical and chemical behaviors of a target system. PMID:19908789

  15. A dynamic oppositional biogeography-based optimization approach for time-varying electrical impedance tomography.

    PubMed

    Rashid, A; Kim, S; Liu, D; Kim, K Y

    2016-06-01

    Dynamic electrical impedance tomography-based image reconstruction using conventional algorithms such as the extended Kalman filter often exhibits inferior performance due to the presence of measurement noise, the inherent ill-posed nature of the problem and its critical dependence on the selection of the initial guess as well as the state evolution model. Moreover, many of these conventional algorithms require the calculation of a Jacobian matrix. This paper proposes a dynamic oppositional biogeography-based optimization (OBBO) technique to estimate the shape, size and location of the non-stationary region boundaries, expressed as coefficients of truncated Fourier series, inside an object domain using electrical impedance tomography. The conductivity of the object domain is assumed to be known a priori. Dynamic OBBO is a novel addition to the family of dynamic evolutionary algorithms. Moreover, it is the first such study on the application of dynamic evolutionary algorithms for dynamic electrical impedance tomography-based image reconstruction. The performance of the algorithm is tested through numerical simulations and experimental study and is compared with state-of-the-art gradient-based extended Kalman filter. The dynamic OBBO is shown to be far superior compared to the extended Kalman filter. It is found to be robust to measurement noise as well as the initial guess, and does not rely on a priori knowledge of the state evolution model. PMID:27203482

  16. Effects of mass layer imperfect bonding on the electrical impedance of a quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Chen, YangYang; Wang, Ji; Du, JianKe; Yang, JiaShi

    2013-11-01

    We study electrically forced vibrations of a crystal plate of AT-cut quartz carrying a thin mass layer operating as a quartz crystal microbalance for mass sensing. The mass layer is imperfectly bonded to the crystal plate with their interface described by the so-called interface-slip model which allows a discontinuity of the tangential interface displacement. Mindlin's equations for piezoelectric plates are used. An analytical solution is obtained. The electrical impedance is calculated. The effects of an elastic interface and a viscoelastic interface are examined.

  17. Mechanical and electrical impedance matching in a piezoelectric beam for Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Koszewnik, A.; Grześ, P.; Walendziuk, W.

    2015-11-01

    A piezoelectric beam is one of transducers for energy harvesting. It provides easy implementation and good performance in changing mechanical stress into electric voltage. In order to maximize output power, it is important to provide mechanical and electrical impedance matching. In the paper the authors proposed a methodology which allows to find values of lumped elements in an electromechanical model after completing appropriate measurements. Due to linear equations, it is possible to model a beam in both mechanical and electrical ways, and match the best load depending of frequency. The proposed model of a piezoelectric cantilever shows a potential use of these devices in micro scale as a cantilever which is a part of a silicon structure. Moreover, in the paper, the authors discuss mechanical aspects of using a weight as the way to tune the piezoelectric beam to a specific frequency. The electrical aspect of matching the source impedance with load, which is based on an electrical model of a piezoelectric transducer, is also presented. In the paper a mathematical model was verified by an experiment in which a laboratory stand equipped with a vibration generator, a piezoelectric energy harvester and acceleration sensors was used.

  18. Electrical transport properties of Mn-Ni-Zn ferrite using complex impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Azizar Rahman, M.; Hossain, A. K. M. Akther

    2014-02-01

    Polycrystalline Mn0.45Ni0.05Zn0.50Fe2O4 was prepared by a standard solid state reaction technique. We report the electrical properties of this ferrite using ac impedance spectroscopy as a function of frequency (20 Hz-10 MHz) at different temperatures (50-350 °C). X-ray diffraction patterns reveal the formation of cubic spinel structure. Complex impedance analysis has been used to separate the grain and grain boundary resistance of this ferrite. The variation of grain and grain boundary conductivities with temperature confirms semiconducting behavior. The dielectric permittivity shows dielectric dispersion at lower frequency and reveals that it has almost the same value on the high-frequency side. The non-coincidence of peaks corresponding to modulus and impedance indicates deviation from Debye-type relaxation. A similar value of activation energy is obtained from impedance and modulus spectra, indicating that charge carriers overcome the same energy barrier during relaxation. Electron hopping is responsible for ac conduction in this ferrite. The electron hopping shifts toward higher frequency with increasing temperature, below which the conductivity is frequency independent. The frequency-independent ac conductivity has been observed at and above 300 °C in the frequency range 20 Hz-1 MHz. This frequency-independent ac conductivity is due to the long-range movement of the mobile charge carriers.

  19. Impedance Alterations in Healthy and Diseased Mice During Electrically Induced Muscle Contraction.

    PubMed

    Sanchez, Benjamin; Li, Jia; Geisbush, Tom; Bardia, Ramon Bragos; Rutkove, Seward B

    2016-08-01

    Alterations in the health of muscles can be evaluated through the use of electrical impedance myography (EIM). To date, however, nearly all work in this field has relied upon the measurement of muscle at rest. To provide an insight into the contractile mechanisms of healthy and disease muscle, we evaluated the alterations in the spectroscopic impedance behavior of muscle during the active process of muscle contraction. The gastrocnemii from a total of 13 mice were studied (five wild type, four muscular dystrophy animals, and four amyotrophic lateral sclerosis animals). Muscle contraction was induced via monophasic current pulse stimulation of the sciatic nerve. Simultaneously, multisine EIM (1 kHz to 1 MHz) and force measurements of the muscle were performed. Stimulation was applied at three different rates to produce mild, moderate, and strong contractions. We identified changes in both single and multifrequency data, as assessed by the Cole impedance model parameters. The processes of contraction and relaxation were clearly identified in the impedance spectra and quantified via derivative plots. Reductions in the center frequency fc were observed during the contraction consistent with the increasing muscle fiber diameter. Different EIM stimulation rate-dependencies were also detected across the three groups of animals. PMID:24800834

  20. High-power CMOS current driver with accurate transconductance for electrical impedance tomography.

    PubMed

    Constantinou, Loucas; Triantis, Iasonas F; Bayford, Richard; Demosthenous, Andreas

    2014-08-01

    Current drivers are fundamental circuits in bioimpedance measurements including electrical impedance tomography (EIT). In the case of EIT, the current driver is required to have a large output impedance to guarantee high current accuracy over a wide range of load impedance values. This paper presents an integrated current driver which meets these requirements and is capable of delivering large sinusoidal currents to the load. The current driver employs a differential architecture and negative feedback, the latter allowing the output current to be accurately set by the ratio of the input voltage to a resistor value. The circuit was fabricated in a 0.6- μm high-voltage CMOS process technology and its core occupies a silicon area of 0.64 mm (2) . It operates from a ± 9 V power supply and can deliver output currents up to 5 mA p-p. The accuracy of the maximum output current is within 0.41% up to 500 kHz, reducing to 0.47% at 1 MHz with a total harmonic distortion of 0.69%. The output impedance is 665 k Ω at 100 kHz and 372 k Ω at 500 kHz. PMID:25073130

  1. Clinical application of Electrical Impedance Tomography in the Present Health Scenario of India

    NASA Astrophysics Data System (ADS)

    Chakraborti, K. L., Dr; Selvamurthy, W., Dr

    2010-04-01

    Early detection of Breast Cancer is currently emerging as a big clinical entity requiring a non invasive, radiation less, harmless, cost effective diagnostic technique. Survival is improved if detected early. Breast Cancer is the second most common cancer in India. Health corporate system of India is urgently requiring a cost effective, noninvasive novel technique like "Electrical Impedance Tomography (EIT)" for screening large poor rural population of India for early diagnosis of Breast Cancer. EIT is the technique to visualize spatial distribution of Electro-impedance (or conductivity) inside the object, such as human body. A medical device which allows imaging of the distribution of conductivity in 3D in regions below the skin surface has been developed and tested. Its purpose is to enable early detection and preliminary diagnosis of breast tumors. The system uses a planar array consisting of 256 electrodes and enables obtaining images of the three-dimensional conductivity distribution in regions below the skin's surface up to several centimeters deep. The developed measuring system and image reconstruction algorithm can be used for breast tissue imaging and diagnostic, in particular for malignant tumor detection. Initially ten patients as control and ten patients with breast lesions have been studied with this new technique. It was found that electrical impedance mammograms from different groups has clear visual distinctions and statistically significant difference in breast glands conductivity. The results are quiet encouraging. EIT may emerge as the first line noninvasive imaging method of choice for screening large population for early detection of breast cancer.

  2. Development of an electrical impedance computed tomographic two-phase flows analyzer. Annual technical report for program renewal

    SciTech Connect

    Jones, O.C.

    1993-05-01

    This progress report details the theoretical development, numerical results, experimental design (mechanical), experimental design (electronic), and experimental results for the research program for the development of an electrical impedance computed tomographic two-phase flow analyzer.

  3. Influence of torso and arm positions on chest examinations by electrical impedance tomography.

    PubMed

    Vogt, B; Mendes, L; Chouvarda, I; Perantoni, E; Kaimakamis, E; Becher, T; Weiler, N; Tsara, V; Paiva, R P; Maglaveras, N; Frerichs, I

    2016-06-01

    Electrical impedance tomography (EIT) is increasingly used in patients suffering from respiratory disorders during pulmonary function testing (PFT). The EIT chest examinations often take place simultaneously to conventional PFT during which the patients involuntarily move in order to facilitate their breathing. Since the influence of torso and arm movements on EIT chest examinations is unknown, we studied this effect in 13 healthy subjects (37  ±  4 years, mean age  ±  SD) and 15 patients with obstructive lung diseases (72  ±  8 years) during stable tidal breathing. We carried out the examinations in an upright sitting position with both arms adducted, in a leaning forward position and in an upright sitting position with consecutive right and left arm elevations. We analysed the differences in EIT-derived regional end-expiratory impedance values, tidal impedance variations and their spatial distributions during all successive study phases. Both the torso and the arm movements had a highly significant influence on the end-expiratory impedance values in the healthy subjects (p  =  0.0054 and p  <  0.0001, respectively) and the patients (p  <  0.0001 in both cases). The global tidal impedance variation was affected by the torso, but not the arm movements in both study groups (p  =  0.0447 and p  =  0.0418, respectively). The spatial heterogeneity of the tidal ventilation distribution was slightly influenced by the alteration of the torso position only in the patients (p  =  0.0391). The arm movements did not impact the ventilation distribution in either study group. In summary, the forward torso movement and the arms' abduction exert significant effects on the EIT waveforms during tidal breathing. We recommend strict adherence to the upright sitting position during PFT when EIT is used. PMID:27200486

  4. Body fat estimations by electrical impedance and infra-red interactance.

    PubMed

    Brodie, D A; Eston, R G

    1992-05-01

    The purpose of this study was to examine body fat estimation using three methods of electrical impedance (the BIA-103 Body Composition Analyser--RJL Systems, Detroit; the BMR 2000 Body Composition Analyzer--Berkeley Medical Research, San Leandro; the BC300 Body Composition Analyzer--Spacelabs, Dallas) and an infra-red interactance method (Futrex 5000 Analyzer--Futrex Inc. Gaithersburg) as an alternative to hydrodensitometry. Five different groups were examined using at least one of the electrical systems and in all cases utilising hydrodensitometry as the criterion method. The results produced highly significant correlations between all methods, but caution is recommended due to the limited common variance in some cases. The individual electrical methods differed from hydrodensitometry by a maximum of 1.1% in obese women, by 21.6% in athletic adults, by 6.2% in the slightly obese group, by 8.1% in normal women and by 56.0% in normal children. Significant mean differences between one of the impedance methods and hydrodensitometry were only noted in two of the groups tested. This suggests, allowing for the limitations of hydrodensitometry itself, that the other three electrical methods appear to be reasonably valid alternatives to underwater weighing, especially for field work of an epidemiological nature. PMID:1521946

  5. Effects of polydeoxyribonucleotides (PDRN) on wound healing: Electric cell-substrate impedance sensing (ECIS).

    PubMed

    Koo, Youngmi; Yun, Yeoheung

    2016-12-01

    Polydeoxyribonucleotides (PDRN) have been explored as an effective treatment for tissue repair in peripheral artery occlusive disease, diabetic foot ulcers, and eye lotion. We report on the effect of polydeoxyribonucleotides (PDRN) on wound healing by using the electric cell-substrate impedance sensing (ECIS) system and viability testing. Human osteoblasts (U2OS) and primary human dermal fibroblasts (HDF) were used to study the effect of PDRN on migration and proliferation. ECIS allowed the creation of a wound by applying high current, and then monitoring the healing process by measuring impedance in real time. The traditional culture-insert gap-closure migration assay was performed and compared with the ECIS wound assay. PDRN-treated U2OS and HDF cells affected cell motilities to wounding site. Viability test results show that HDF and U2OS proliferation depended on PDRN concentration. Based on the results, a PDRN compound can be useful in wound healing associated with bone and skin. PMID:27612747

  6. Electric field imaging of a high impedance surface for GNSS array decoupling application

    NASA Astrophysics Data System (ADS)

    Prost, Daniel; Issac, François; Martel, Cédric; Capet, Nicolas; Sokoloff, Jérôme; Pascal, Olivier

    2015-10-01

    An original method of characterization of high impedance surfaces (HIS) is presented to exhibit electric field patterns. The electric field frames are obtained through a resistive film located in the near field domain of the HIS. The film heating is recorded using an infrared camera and gives after post-processing electric field magnitude profiles. We applied this technique to a HIS specially tuned for reducing mutual coupling in a global navigation satellite systems (GNSS) array designed for the E5 Galileo band. The mushroom-like HIS, designed and realized with the help of simulation, is located near the ground plane of a micro-strip line which allows S parameter characterization. Present measurement enables near field characterization and field structure analysis, and is therefore a complement to usual analysis. Moreover, the technique shows the very special field structure, including sub-lambda details, created by the HIS and more generally by metamaterial structures.

  7. Considerations on electrical impedance measurements of electrolyte solutions in a four-electrode cell

    NASA Astrophysics Data System (ADS)

    Chaparro, C. V.; Herrera, L. V.; Meléndez, A. M.; Miranda, D. A.

    2016-02-01

    A tetrapolar probe to measure the electrical properties of electrolyte solutions was implemented with gold electrodes according to the van der Pauw method. Electrical impedance spectroscopy (EIS) measurements of different concentrations of phosphate buffer saline (PBS) solution and an oral mucosal tissue sample dispersed in PBS were performed in the galvanostatic mode using a four-electrode cell (tetrapolar probe). Taking advantage of using a potentiostat/galvanostat for carrying out the electrical measurements, a simple and rapid method using a three-electrode electrochemical cell is described for: a) cleaning of electrodes, b) verification of surface chemical state of electrode material and c) choice of current supplied to electrodes for EIS measurements. Results of this research shown a depolarization effect due to the addition of oral mucosa tissue cells into the PBS solution.

  8. A new experimental device to evaluate eye ulcers using a multispectral electrical impedance technique

    NASA Astrophysics Data System (ADS)

    Bellotti, Mariela I.; Bast, Walter; Berra, Alejandro; Bonetto, Fabián J.

    2011-07-01

    We present a novel experimental technique to determine eye ulcers in animals using a spectral electrical impedance technique. We expect that this technique will be useful in dry eye syndrome. We used a sensor that is basically a platinum (Pt) microelectrode electrically insulated by glass from a cylindrical stainless steel counter-electrode. This sensor was applied to the naked eye of New Zealand rabbits (2.0-3.5 kg in weight). Whereas half of the eyes were normal (control), we applied to the remainder a few drops of 20% (v/v) alcohol to produce an ulcer in the eye. Using a multispectral electrical impedance system we measured ulcerated and control eyes and observed significant difference between normal and pathological samples. We also investigated the effects of different applied pressures and natural degradation of initially normal eyes as a function of time. We believe that this technique could be sufficiently sensitive and repetitive to help diagnose ocular surface diseases such as dry eye syndrome.

  9. Use of electrical impedance spectroscopy to detect malignant and potentially malignant oral lesions

    PubMed Central

    Murdoch, Craig; Brown, Brian H; Hearnden, Vanessa; Speight, Paul M; D’Apice, Katy; Hegarty, Anne M; Tidy, John A; Healey, T Jamie; Highfield, Peter E; Thornhill, Martin H

    2014-01-01

    The electrical properties of tissues depend on their architecture and cellular composition. We have previously shown that changes in electrical impedance can be used to differentiate between different degrees of cervical dysplasia and cancer of the cervix. In this proof-of-concept study, we aimed to determine whether electrical impedance spectroscopy (EIS) could distinguish between normal oral mucosa; benign, potentially malignant lesions (PML); and oral cancer. EIS data were collected from oral cancer (n=10), PML (n=27), and benign (n=10) lesions. EIS from lesions was compared with the EIS reading from the normal mucosa on the contralateral side of the mouth or with reference spectra from mucosal sites of control subjects (n=51). Healthy controls displayed significant differences in the EIS obtained from different oral sites. In addition, there were significant differences in the EIS of cancer and high-risk PML versus low-risk PML and controls. There was no significant difference between benign lesions and normal controls. Study subjects also deemed the EIS procedure considerably less painful and more convenient than the scalpel biopsy procedure. EIS shows promise at distinguishing among malignant, PML, and normal oral mucosa and has the potential to be developed into a clinical diagnostic tool. PMID:25285005

  10. [Estimation of normal body volumes in children by the measurement of total electrical impedance (author's transl)].

    PubMed

    Peyramond, D; Tholly, F; Bertoye, A

    1980-03-01

    The theoretical fluid volume of 41 normal children (mean age 8 years 9 months) was estimated from anthropometric data: height, weight, wrist circumference, and body surface. The correlation between this method and the conventional methods of determining total body water using tritiated water or of extracellular fluid volume using stable bromide or bromide 82 is very good. The real fluid volumes have been measured using total body electrical impedance at low frequency (Z5 kHz) and high frequency (Z1 MHz). The correlation of these results with those obtained by anthropometry is very satisfactory (r = 0.89; p < 0,001). PMID:7469697

  11. A Wide Bandwidth Model for the Electrical Impedance of Magnetic BearingS

    NASA Technical Reports Server (NTRS)

    Meeker, David C.; Maslen, Eric H.; Noh, Myounggyu D.

    1996-01-01

    Magnetic bearings are often designed using magnetic circuit theory. When these bearings are built, however, effects not included in the usual circuit theory formulation have a significant influence on bearing performance. Two significant sources of error in the circuit theory approach are the neglect of leakage and fringing effects and the neglect of eddy current effects. This work formulates an augmented circuit model in which eddy current and flux leakage and fringing effects are included. Through the use of this model, eddy current power losses and actuator bandwidth can be derived. Electrical impedance predictions from the model are found to be in good agreement with experimental data from a typical magnetic bearing.

  12. The in-situ characterization of a transesterification reaction using electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Cho, Sungjin

    Impedance Spectroscopy has been used in the in-situ monitoring of a transesterfication reaction of soybean biodiesel. This paper describes the application of Electrical Impedance Spectroscopy (EIS) to observe and characterize the transesterfication reaction and its interfacial behavior phenomena electrically. In particular, the dielectric properties of soybean biodiesel were measured at broad range frequencies from 10-2 to 106 Hz at different temperatures, methanol molar ratio to biodiesel, concentration of catalyst and reaction time. Measurement of dielectric property have provided an important approach to understanding the structure of matter. Measurements of the dielectric properties are a reliable and efficient method for evaluating the biodiesel production to determine their quality and yield for reducing the production cost. The dielectric constant (epsilon') and loss (epsilon") are the most convenient indicators for quality control in commercial biodiesel manufacturing. Dielectric properties were correlated with chemically measured changes in soybean oil such as free fatty acids, amount of catalyst and alcohols at different temperatures as well as reaction times. It was observed that there is a good correlation between the dielectric constant (epsilon') and loss (epsilon") in soybean biodiesel. The result indicated that the dielectric properties increased with the (1) increasing temperature (2) increasing methanol; (3) increasing catalyst; (4) increasing reaction time. Dielectric properties was a useful index for the rapid quality evaluation of soybean biodiesel. Dielectric properties were compared to conventional methods of analysis (Infrared Spectroscopy) for evaluating the quality of soybean biodiesel. The results indicated that dielectric constant and dielectric loss are essential measurement for predicting the best biodiesel yield. Moreover, the electrical impedance parameters such as bulk resistance (Rb), bulk capacitance (Cb) and time constant(tau b

  13. Measurement of lung function using Electrical Impedance Tomography (EIT) during mechanical ventilation

    NASA Astrophysics Data System (ADS)

    Nebuya, Satoru; Koike, Tomotaka; Imai, Hiroshi; Noshiro, Makoto; Brown, Brian H.; Soma, Kazui

    2010-04-01

    The consistency of regional lung density measurements as estimated by Electrical Impedance Tomography (EIT), in eleven patients supported by a mechanical ventilator, was validated to verify the feasibility of its use in intensive care medicine. There were significant differences in regional lung densities between the normal lung and diseased lungs associated with pneumonia, atelectasis and pleural effusion (Steel-Dwass test, p < 0.05). Temporal changes in regional lung density of patients with atelectasis were observed to be in good agreement with the results of clinical diagnosis. These results indicate that it is feasible to obtain a quantitative value for regional lung density using EIT.

  14. Electrical impedance measurements in the arm and the leg during a thirty day bed rest study

    NASA Technical Reports Server (NTRS)

    Cardus, David; Jaweed, Mazher; McTaggart, Wesley

    1995-01-01

    The need to detect, follow, and understand the effects of gravity on body fluid distribution is a constant stimulus to the quest for new techniques in this area of research. One of these techniques is electrical bioimpedance spectroscopy (BIS). Although not new, this is a technique whose applications to biomedical research are fairly recent. What is new is the development of instrumentation that has made practical the use of impedance spectroscopy in the biomedical setting, particularly in studies involving human subjects. The purpose of this paper is to report impedance spectroscopy observations made on a subject who was submitted to bed rest for a period of thirty days. These observations were made as part of a study on muscle atrophy during a thirty day head down bed rest. Since bed rest studies are very costly in human and financial terms, and technically difficult to realize, we felt that even though the present study deals only with a single case it was worthy of reporting because it illustrates kinds of questions impedance spectroscopy may help to answer in microgravity research.

  15. Recognition of Fibrotic Infarct Density by the Pattern of Local Systolic-Diastolic Myocardial Electrical Impedance

    PubMed Central

    Amorós-Figueras, Gerard; Jorge, Esther; García-Sánchez, Tomás; Bragós, Ramón; Rosell-Ferrer, Javier; Cinca, Juan

    2016-01-01

    Myocardial electrical impedance is a biophysical property of the heart that is influenced by the intrinsic structural characteristics of the tissue. Therefore, the structural derangements elicited in a chronic myocardial infarction should cause specific changes in the local systolic-diastolic myocardial impedance, but this is not known. This study aimed to characterize the local changes of systolic-diastolic myocardial impedance in a healed myocardial infarction model. Six pigs were successfully submitted to 150 min of left anterior descending (LAD) coronary artery occlusion followed by reperfusion. 4 weeks later, myocardial impedance spectroscopy (1–1000 kHz) was measured at different infarction sites. The electrocardiogram, left ventricular (LV) pressure, LV dP/dt, and aortic blood flow (ABF) were also recorded. A total of 59 LV tissue samples were obtained and histopathological studies were performed to quantify the percentage of fibrosis. Samples were categorized as normal myocardium (<10% fibrosis), heterogeneous scar (10–50%) and dense scar (>50%). Resistivity of normal myocardium depicted phasic changes during the cardiac cycle and its amplitude markedly decreased in dense scar (18 ± 2 Ω·cm vs. 10 ± 1 Ω·cm, at 41 kHz; P < 0.001, respectively). The mean phasic resistivity decreased progressively from normal to heterogeneous and dense scar regions (285 ± 10 Ω·cm, 225 ± 25 Ω·cm, and 162 ± 6 Ω·cm, at 41 kHz; P < 0.001 respectively). Moreover, myocardial resistivity and phase angle correlated significantly with the degree of local fibrosis (resistivity: r = 0.86 at 1 kHz, P < 0.001; phase angle: r = 0.84 at 41 kHz, P < 0.001). Myocardial infarcted regions with greater fibrotic content show lower mean impedance values and more depressed systolic-diastolic dynamic impedance changes. In conclusion, this study reveals that differences in the degree of myocardial fibrosis can be detected in vivo by local measurement of phasic systolic

  16. Electric-controlled scanning Luneburg lens based on metamaterials

    NASA Astrophysics Data System (ADS)

    Wang, Min; Huang, Cheng; Pu, Ming-Bo; Hu, Cheng-Gang; Pan, Wen-Bo; Zhao, Ze-Yu; Luo, Xian-Gang

    2013-05-01

    The feasibility of 360∘ scanning Luneburg lens based on electric-controlled metamaterial is analyzed. When the line source is fixed in the center of the lens, the direction of radiated beam can be tuned by adjusting the bias voltages distribution applied to the varactors in each unit cell. By introducing an artificial reflective plane, the gain of the antenna can be further enhanced. The minimal step of scanning angle obtained in simulation is only 7∘, which can be further decreased by increasing the dimension and the number of unit cell used in Luneburg lens.

  17. Wideband Fully-Programmable Dual-Mode CMOS Analogue Front-End for Electrical Impedance Spectroscopy.

    PubMed

    Valente, Virgilio; Demosthenous, Andreas

    2016-01-01

    This paper presents a multi-channel dual-mode CMOS analogue front-end (AFE) for electrochemical and bioimpedance analysis. Current-mode and voltage-mode readouts, integrated on the same chip, can provide an adaptable platform to correlate single-cell biosensor studies with large-scale tissue or organ analysis for real-time cancer detection, imaging and characterization. The chip, implemented in a 180-nm CMOS technology, combines two current-readout (CR) channels and four voltage-readout (VR) channels suitable for both bipolar and tetrapolar electrical impedance spectroscopy (EIS) analysis. Each VR channel occupies an area of 0.48 mm 2 , is capable of an operational bandwidth of 8 MHz and a linear gain in the range between -6 dB and 42 dB. The gain of the CR channel can be set to 10 kΩ, 50 kΩ or 100 kΩ and is capable of 80-dB dynamic range, with a very linear response for input currents between 10 nA and 100 μ A. Each CR channel occupies an area of 0.21 mm 2 . The chip consumes between 530 μ A and 690 μ A per channel and operates from a 1.8-V supply. The chip was used to measure the impedance of capacitive interdigitated electrodes in saline solution. Measurements show close matching with results obtained using a commercial impedance analyser. The chip will be part of a fully flexible and configurable fully-integrated dual-mode EIS system for impedance sensors and bioimpedance analysis. PMID:27463721

  18. Detection of small bleeds in the brain with electrical impedance tomography.

    PubMed

    Boverman, Gregory; Kao, Tzu-Jen; Wang, Xin; Ashe, Jeffrey M; Davenport, David M; Amm, Bruce C

    2016-06-01

    In this paper, we describe and assess feasibility of instrumentation and algorithms for detecting bleeding due to hemorrhagic strokes and traumatic brain injury using electrical impedance tomography, a novel biomedical diagnostic modality in which the body is probed noninvasively with generally imperceptible alternating currents applied in patterns to a set of electrodes placed in contact with the skin. We focus on the GENESIS instrument developed by GE Global Research and on the achievability of our goal to detect a bleed in the center of the head with a volume of several ml. Our main topic is compensation for the large changes in voltages that tend to occur when the electrodes are in contact with biological media, specifically either human subjects or with vegetable matter proxies which seem to exhibit the same 'drift' phenomenon. We show that these changes in voltages can be modeled by assuming that each electrode is attached to the body via a discrete complex impedance whose value is time-varying and describe how this discrete component value can be estimated and largely compensated-for. We compare this discrete model with changes in contact impedances estimated using the complete electrode model showing that the two models are roughly comparable in their ability to explain the data from a single human subject experiment with electrodes attached to the head. In a simulation study, we demonstrate that it is possible to detect a small bleed in the center of the head even in the case of large changes in electrode impedances, which can be treated as nuisance parameters. PMID:27203851

  19. Pre-contraction dynamic electrical impedance myography of the forearm finger flexors.

    PubMed

    Shiffman, C A

    2016-02-01

    Electrical activity in the sensory-motor and supplementary motor areas of the cerebral cortex is known to occur during a 'readiness interval', extending up to 2 s before the relevant muscle actually contracts. This paper presents evidence that there are also changes in the properties of the muscle itself during a similar preparatory period, as revealed by dynamic electrical impedance myography. 11 healthy subjects aged 23.5 ± 2.5 years were asked to perform a series of isometric gripping exercises during which the force, resistance and reactance of the forearm finger flexor muscles were monitored. A change in reactance, ΔX, or resistance, ΔR, which occurred before the generation of force, ΔF, was dubbed a 'PIC', shorthand for precontraction impedance change (subject to criteria to rule out the possibility of simple 'noise'), of which 1206 qualified in the entire subject cohort. Such PIC's are statistically well correlated when expressed in terms of differences between PIC and force onset times (r ≈ 0.9, p ≈ 0). This is demonstrated using a variation on the 'computer of average transients' method. Precontraction impedance changes (PICs) occurring as much as 2 s before the onset of force generation were found, in qualitative agreement with precontraction EEG activity reported in the literature. Also, a subset of PIC's was found in which the scaled and time-shifted ΔX(t) was virtually identical to ΔF(t). Since the occurrence and timing of all the PICs depend on oral commands, it is clear that the auditory cortex is likely involved, but the detailed mechanism coupling brain activity with PICs is not known. PMID:26814557

  20. Design and simulation of superconducting Lorentz Force Electrical Impedance Tomography (LFEIT)

    NASA Astrophysics Data System (ADS)

    Shen, Boyang; Fu, Lin; Geng, Jianzhao; Zhang, Xiuchang; Zhang, Heng; Dong, Qihuan; Li, Chao; Li, Jing; Coombs, T. A.

    2016-05-01

    Lorentz Force Electrical Impedance Tomography (LFEIT) is a hybrid diagnostic scanner with strong capability for biological imaging, particularly in cancer and haemorrhages detection. This paper presents the design and simulation of a novel combination: a superconducting magnet together with LFEIT system. Superconducting magnets can generate magnetic field with high intensity and homogeneity, which could significantly enhance the imaging performance. The modelling of superconducting magnets was carried out using Finite Element Method (FEM) package, COMSOL Multiphysics, which was based on Partial Differential Equation (PDE) model with H-formulation coupling B-dependent critical current density and bulk approximation. The mathematical model for LFEIT system was built based on the theory of magneto-acoustic effect. The magnetic field properties from magnet design were imported into the LFEIT model. The basic imaging of electrical signal was developed using MATLAB codes. The LFEIT model simulated two samples located in three different magnetic fields with varying magnetic strength and homogeneity.

  1. Measurement of Two-Phase Flow Fields by Application of Dynamic Electrical Impedance Imaging

    SciTech Connect

    Kim, KyungYoun; Kang, Sook In; Kim, Ho Chan; Kim, Sin; Lee, Yoon Joon; Kim, Min Chan; Anghaie, Samim

    2002-07-01

    This study presents a visualization technique for the phase distribution in a two-phase flow field with an electrical impedance imaging technique, which reconstructs the resistivity distribution with electrical responses that are determined by corresponding excitations. Special emphasis is placed on the development of dynamic imaging technique for two-phase system undergoing a rapid transient, which could not be visualized with conventional static imaging techniques. The proposed algorithm treats the image reconstruction problem as a nonlinear state estimation problem and the unknown state (resistivity distribution, i.e. phase distribution) is estimated with the aid of a Kalman filter in a minimum mean square error sense. Several illustrative examples with computer simulations are successfully provided to verify the reconstruction performance of the proposed algorithm. (authors)

  2. Influence of neutron flux, frequency and temperature to electrical impedance of nano silica particles

    SciTech Connect

    Huseynov, Elchin E-mail: hus.elchin@gmail.com; Garibov, Adil; Mehdiyeva, Ravan; Andreja, Eršte; Rustamov, Anar

    2014-11-15

    We studied electric impedance of SiO{sub 2} nanomaterial at its initial state and after being exposed to continuous neutron irradiation for up to 20 hours. In doing so we employed a flux of neutrons of 2x10{sup 13} n⋅cm{sup −2}s{sup −1} while the frequency and temperature ranges amounted to 0,09 – 2.3 MHz and 100 – 400 K correspondingly. Analysis in terms of the Cole-Cole expression revealed that with increasing irradiation period the polarization and relaxation times decrease as a result of combination of nanoparticles. Moreover, it is demonstrated that the electric conductivity of samples, on the other hand, increases with the increasing irradiation period. At low temperatures formations of clusters at three distinct states with different energies were resolved.

  3. Design of an Electrical Impedance Tomography Sensor for Flow Measurement in an Oscillatory Baffled Reactor

    NASA Astrophysics Data System (ADS)

    Vilar, G.; Williams, R. A.; Wang, M.

    2007-06-01

    In this paper, a new application of electrical impedance tomography (EIT) for an advanced on-line measurement is presented. This application involves the design, manufacture and adaptation of an EIT sensor for the measurement in an oscillatory baffled reactor (OBR). The main goal is to develop of a novel measurement and modeling method for control of the OBR. The reactor itself enables the production of water-in-oil/oil-in water emulsions along with the use of chemical reagents for a variety of manufacturing processes. Use of electrical tomography facilitates detailed measurement of the concentration and flow of components in the reactor. The paper reports on design philosophy of the EIT for this application that has not, to our knowledge, been reported previously.

  4. Enhanced health monitoring of fibrous composites with aligned carbon nanotube networks and electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Tallman, T.; Semperlotti, F.; Wang, K. W.

    2012-04-01

    The high strength to weight ratio of fibrous composites such as glass-fiber reinforced polymers (GFRP) makes them prominent structural materials. However, their laminar nature is susceptible to delamination failure the onset of which traditional structural health monitoring (SHM) techniques cannot reliably and accurately detect. Carbon nano-tubes (CNT) have been recently used to tailor the electrical conductivity of polymer based materials that otherwise behave as insulators. The occurrence of damage in the polymer matrix produces localized changes in conductivity which can be tracked using electrical impedance tomography (EIT). This paper explores combining advances in composite manufacturing with EIT to develop a SHM technique that exploits anisotropic conductance monitoring for enhanced delamination and matrix crack detection.

  5. Monitoring of lobectomy in cystic fibrosis with electrical impedance tomography - a new diagnostic tool.

    PubMed

    Lehmann, Sylvia; Tenbrock, Klaus; Schrading, Simone; Pikkemaat, Robert; Antink, Christoph Hoog; Santos, Susana; Spillner, Jan Wilhelm; Wagner, Norbert; Leonhardt, Steffen

    2014-12-01

    Electrical impedance tomography (EIT) is a radiation-free technique generating cross-sectional images of the lung. EIT visualizes global and regional ventilation by illustrating the distribution of electrical bioimpedance. With an electrode belt around the patient's thorax, rotating injection-couples of a harmless alternating current allow voltage measurement of the remaining electrodes. This enables the reconstruction of a tomogram with highly dynamic changes within ventilation. We report on a female six-year-old patient with cystic fibrosis and complete destruction of the upper and middle lobe of the right lung. Lobectomy, a rare therapeutic option in patients with cystic fibrosis that needs to be considered in cases of severe localized destruction, was performed. We show a pre- and postoperative documentation of static (radiology) and dynamic investigation tools (spirometry) in correlation with EIT as a new non-invasive and radiation-free diagnostic tool for this patient group. PMID:25153206

  6. Model-aware Newton-type inversion scheme for electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Winkler, Robert; Rieder, Andreas

    2015-04-01

    Electrical impedance tomography is a non-invasive method for imaging the electrical conductivity of an object from voltage measurements on its surface. This inverse problem suffers in three respects: It is highly nonlinear, severely ill-posed and highly under-determined. To obtain yet reasonable reconstructions, maximal information needs to be gathered from the model and extracted from the data in all stages of the reconstruction procedure. We will present a holistic reconstruction framework which estimates the unknown model-specific parameters, i.e. background conductivity, contact impedance, and noise level, before solving the full nonlinear problem with a Newton-type method. Therein, a novel conductivity transformation decreases nonlinearity while a weighting scheme resolves the under-determinedness by promoting the reconstruction of piecewise constant conductivities. This way we increase robustness, speed, and reconstruction accuracy. Moreover, our method is easy to use and applies to a wide range of settings as it is free of design parameters. Being an absolute imaging method, no measured calibration data is required. We demonstrate the performance of this concept numerically for simulated and measured data.

  7. Bias-dependent model of the electrical impedance of ionic polymer-metal composites.

    PubMed

    Cha, Youngsu; Porfiri, Maurizio

    2013-02-01

    In this paper, we analyze the charge dynamics of ionic polymer-metal composites (IPMCs) in response to voltage inputs composed of a large dc bias and a small superimposed time-varying voltage. The IPMC chemoelectrical behavior is described through the modified Poisson-Nernst-Planck framework, in which steric effects are taken into consideration. The physics of charge build-up and mass transfer in the proximity of the high surface electrodes is modeled by schematizing the IPMC as the stacked sequence of five layers, in which the ionomeric membrane is separated from the metal electrodes by two composite layers. The method of matched asymptotic expansions is used to derive a semianalytical solution for the concentration of mobile counterions and the electric potential in the IPMC, which is, in turn, used to establish an equivalent circuit model for the IPMC electrical response. The circuit model consists of the series connection of a resistor and two complex elements, each constituted by the parallel connection of a capacitor and a Warburg impedance. The resistor is associated with ion transport in the ionomeric membrane and is independent of the dc bias. The capacitors and the Warburg impedance idealize charge build-up and mass transfer in the vicinity of the electrodes and their value is controlled by the dc bias. The proposed approach is validated against experimental results on in-house fabricated IPMCs and the accuracy of the equivalent circuit is assessed through comparison with finite element results. PMID:23496522

  8. A Multilayer MEMS Platform for Single-Cell Electric Impedance Spectroscopy and Electrochemical Analysis

    PubMed Central

    Dittami, Gregory M.; Ayliffe, H. Edward; King, Curtis S.; Rabbitt, Richard D.

    2008-01-01

    The fabrication and characterization of a microchamber electrode array for electrical and electrochemical studies of individual biological cells are presented. The geometry was tailored specifically for measurements from sensory hair cells isolated from the cochlea of the mammalian inner ear. Conventional microelectromechanical system (MEMS) fabrication techniques were combined with a heat-sealing technique and polydimethylsiloxane micromolding to achieve a multilayered microfluidic system that facilitates cell manipulation and selection. The system allowed for electrical stimulation of individual living cells and interrogation of excitable cell membrane dielectric properties as a function of space and time. A three-electrode impedimetric system was incorporated to provide the additional ability to record the time-dependent concentrations of specific biochemicals in microdomain volumes near identified regions of the cell membrane. The design and fabrication of a robust fluidic and electrical interface are also described. The interface provided the flexibility and simplicity of a “cartridge-based” approach in connecting to the MEMS devices. Cytometric measurement capabilities were characterized by using electric impedance spectroscopy (1 kHz–10 MHz) of isolated outer hair cells. Chemical sensing capability within the microchannel recording chamber was characterized by using cyclic voltammetry with varying concentrations of potassium ferricyanide (K3Fe(CN)6). Chronoamperometric recordings of electrically stimulated PC12 cells highlight the ability of the platform to resolve exocytosis events from individual cells. PMID:19756255

  9. In vivo bioimpedance measurement of healthy and ischaemic rat brain: implications for stroke imaging using electrical impedance tomography.

    PubMed

    Dowrick, T; Blochet, C; Holder, D

    2015-06-01

    In order to facilitate the imaging of haemorrhagic and ischaemic stroke using frequency difference electrical impedance tomography (EIT), impedance measurements of normal and ischaemic brain, and clotted blood during haemorrhage, were gathered using a four-terminal technique in an in vivo animal model, a first for ischaemic measurements. Differences of 5-10% in impedance were seen between the frequency spectrums of healthy and ischaemic brain, over the frequency range 0-3 kHz, while the spectrum of blood was predominately uniform. The implications of imaging blood/ischaemia in the brain using electrical impedance tomography are discussed, supporting the notion that it will be possible to differentiate stroke from haemorrhage. PMID:26006171

  10. THE ELECTRICAL IMPEDANCE OF MUSCLE DURING THE ACTION OF NARCOTICS AND OTHER AGENTS.

    PubMed

    Guttman, R

    1939-05-20

    1. The effect of certain inorganic cations upon the electrical impedance of the sartorius muscle of the frog was investigated. While Na, K, and Mg have little effect upon the resistance of muscle, Ba and Ca cause it to fall. The use of physiologically "unbalanced" salt solution does not in itself seem to affect muscle impedance. 2. The time course of the effect upon muscle impedance of the penetration of substances into the intercellular spaces was studied by treating the muscle with sugar solutions. Half of the effect is over in three-quarters of a minute when the sugar solution is permitted to circulate past both sides of the muscle. This sets an upper limit for the time necessary for inorganic cations and organic narcotics to reach the cell surfaces. The action of inorganic cations and organic narcotics upon muscle is slow compared to the time necessary for them to reach the scene of action. The penetration of the sugar solutions into the intercellular spaces of muscle was found to follow the well known diffusion law, the amount diffusing in being proportional to the square root of the time. Average values of 77.7 per cent for rho, the volume concentration of fibers; 231 ohms specific resistance for r(2), the resistance of the interior of the fibers; and 71.0 degrees for theta, the phase angle of the impedance locus, were obtained for the muscle in Ringer's solution. How these values change when the muscle is placed in various concentrations of sugar was also studied. 3. The action of a number of organic narcotics upon muscle was studied. All decrease 1000 cycle resistance if the concentration is sufficiently high. A detailed analysis of the action of the narcotic, iso-amyl carbamate, was made, and it was noted that low concentrations increase resistance while higher concentrations decrease it. By investigating the effect of narcotics upon muscle impedance over a wide frequency range, it was found that during narcosis the resistance of the fiber membranes first

  11. Electron Impedances

    SciTech Connect

    P Cameron

    2011-12-31

    It is only recently, and particularly with the quantum Hall effect and the development of nanoelectronics, that impedances on the scale of molecules, atoms and single electrons have gained attention. In what follows the possibility that characteristic impedances might be defined for the photon and the single free electron is explored is some detail, the premise being that the concepts of electrical and mechanical impedances are relevant to the elementary particle. The scale invariant quantum Hall impedance is pivotal in this exploration, as is the two body problem and Mach's principle.

  12. Distributed network imaging and electrical impedance tomography of minimally invasive surgery.

    PubMed

    Otten, David M; Onik, Gary; Rubinsky, Boris

    2004-04-01

    Minimally invasive surgery has become highly dependent on imaging. For instance, the effectiveness of cryosurgery in treating cancer is dependent on knowledge of freezing extent, and relies on real-time imaging techniques for monitoring. However, medical imaging is often very expensive and therefore not available to most of the world population. Here we propose the concept of distributed network imaging (DNI) which could make medical imaging and minimally invasive surgery available to all who need these advanced medical modalities. We demonstrate the concept through electrical impedance tomography (EIT) of cryosurgery. The central idea is to develop an inexpensive measurend (data collection hardware) at a remote site and then to connect the measurend apparatus to an advanced image reconstruction server, which can serve a large number of distributed measurends at remote sites, using existing communication conduits (Ethernet, telephone, satellite, etc.). These conduits transfer the raw data from the measurend to the server and the reconstructed image from the server to the measurend. Electrical impedance tomography (EIT) is an imaging modality which utilizes tissue impedance variation to construct an image. The EIT measurend which consists of electrodes, a power supply, and means to measure voltage is inexpensive, and therefore suitable for DNI. EIT is also very well-suited to imaging cryosurgery since frozen tissue impedance is much higher than that of unfrozen tissue. In this study, we first develop numerical models to illustrate the theoretical ability of EIT to image cryosurgery. We begin with a simplified two dimensional model, and then extend the study to the more appropriate three dimensional model. Our simulated finite element phantoms and pixel-based Newton-Raphson reconstruction algorithms were able to produce easily identifiable images of frozen regions within tissue. Then, we demonstrate the feasibility of the DNI concept though a case study using EIT to

  13. Electrical impedance tomography-based sensing skin for quantitative imaging of damage in concrete

    NASA Astrophysics Data System (ADS)

    Hallaji, Milad; Seppänen, Aku; Pour-Ghaz, Mohammad

    2014-08-01

    This paper outlines the development of a large-area sensing skin for damage detection in concrete structures. The developed sensing skin consists of a thin layer of electrically conductive copper paint that is applied to the surface of the concrete. Cracking of the concrete substrate results in the rupture of the sensing skin, decreasing its electrical conductivity locally. The decrease in conductivity is detected with electrical impedance tomography (EIT) imaging. In previous works, electrically based sensing skins have provided only qualitative information on the damage on the substrate surface. In this paper, we study whether quantitative imaging of the damage is possible. We utilize application-specific models and computational methods in the image reconstruction, including a total variation (TV) prior model for the damage and an approximate correction of the modeling errors caused by the inhomogeneity of the painted sensing skin. The developed damage detection method is tested experimentally by applying the sensing skin to polymeric substrates and a reinforced concrete beam under four-point bending. In all test cases, the EIT-based sensing skin provides quantitative information on cracks and/or other damages on the substrate surface: featuring a very low conductivity in the damage locations, and a reliable indication of the lengths and shapes of the cracks. The results strongly support the applicability of the painted EIT-based sensing skin for damage detection in reinforced concrete elements and other substrates.

  14. Electrical impedance map (EIM) for margin assessment during robot-assisted laparoscopic prostatectomy (RALP) using a microendoscopic probe

    NASA Astrophysics Data System (ADS)

    Mahara, Aditya; Khan, Shadab; Schned, Alan R.; Hyams, Elias S.; Halter, Ryan J.

    2015-03-01

    Positive surgical margins (PSMs) found following prostate cancer surgery are a significant risk factor for post-operative disease recurrence. Noxious adjuvant radiation and chemical-based therapies are typically offered to men with PSMs. Unfortunately, no real-time intraoperative technology is currently available to guide surgeons to regions of suspicion during the initial prostatectomy where immediate surgical excisions could be used to reduce the chance of PSMs. A microendoscopic electrical impedance sensing probe was developed with the intention of providing real-time feedback regarding margin status to surgeons during robot-assisted laparoscopic prostatectomy (RALP) procedures. A radially configured 17-electrode microendoscopic probe was designed, constructed, and initially evaluated through use of gelatin-based phantoms and an ex vivo human prostate specimen. Impedance measurements are recorded at 10 frequencies (10 kHz - 100 kHz) using a high-speed FPGA-based electrical impedance tomography (EIT) system. Tetrapolar impedances are recorded from a number of different electrode configurations strategically chosen to sense tissue in a pre-defined sector underlying the probe face. A circular electrical impedance map (EIM) with several color-coded pie-shaped sectors is created to represent the impedance values of the probed tissue. Gelatin phantom experiments show an obvious distinction in the impedance maps between high and low impedance regions. Similarly, the EIM generated from the ex vivo prostate case shows distinguishing features between cancerous and benign regions. Based on successful development of this probe and these promising initial results, EIMs of additional prostate specimens are being collected to further evaluate this approach for intraoperative surgical margin assessment during RALP procedures.

  15. Fourier analysis of electrical impedance variations in urinary bladder during changes of intravesical pressure

    NASA Astrophysics Data System (ADS)

    Sivkov, A. V.; Mudraya, I. S.; Revenko, S. V.; Ibragimov, A. R.; Nesterov, A. V.; Gavrilov, I. Yu; Kirpatovsky, V. I.; Stranadko, M. V.

    2010-04-01

    Original hardware and software system was used to record and analyze the variations of electrical impedance of the urinary bladder in narcotized rats (n=7) at rest, during instillation of physiological saline into the bladder resulted in elevation of intravesical pressure, and during subsequent urination accompanied by intravesical pressure release. Fourier analysis of impedance variations revealed three periodic components with the frequencies of heartbeat, respiration, and the Mayer wave (~0.1 Hz). In resting bladder, the amplitude of Mayer and respiratory spectrum peaks were high, and they increased to a different extent during physiological elevation of intravesical pressure, while a small cardiac peak did not changed significantly and tended to decrease at high intravesical pressure. Urination released intravesical pressure and restored all the peaks to the resting level. It is hypothesized that Mayer and respiratory bioimpedance oscillations of urinary bladder are neural in origin, while the cardiac peak is mainly determined by hydrodynamic arterial pulsations. The novel method can assess vesical circulation and its neural control at various phases of bladder activity.

  16. Measurement of Electrical Activation Energy in Black CVD Diamond Using Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ye, Haitao; Williams, Oliver A.; Jackman, Richard B.

    Dc current-voltage (I-V) measurement, Hall measurement, Deep-level transient-spectroscopy (DLTS), and flatband capacitance measurement have been used to investigate electrical activation energies in diamond. However, the deviations still exist in the published activation energies obtained by these methods. In this paper, we report the first measurement of impedance on free-standing diamond films from 0.1Hz to 10MHz up to 300°C. A wide range of CVD materials have been investigated, but here we concentrate on `black' diamond grown by MWPECVD. The Cole-Cole (Z' via Z'') plots are well fitted to a RC parallel circuit model and the equivalent Resistance and Capacitance for the diamond films have been estimated using the Zview curve fitting. The results show only one single semicircle response at each temperature measured. It was found that the resistance decreases from 62 MΩ at room temperature to 4 KΩ at 300°C, with an activation energy around 0.15eV. The equivalent capacitance is maintained at the level of 102 pF up to 300°C suggesting that the diamond grain boundaries are dominating the conduction. At 400°C, the impedance at low frequencies shows a linear tail, which can be explained that the AC polarization of diamond/Au interface occurs.

  17. Microneedle Electrode Array for Electrical Impedance Myography to Characterize Neurogenic Myopathy.

    PubMed

    Li, Zhao; Li, Yi; Liu, Mingsheng; Cui, Liying; Yu, Yude

    2016-05-01

    Electrical impedance myography (EIM) is a noninvasive technique for neuromuscular assessment, wherein a low-intensity alternating current is applied to a muscle, and the consequent surface voltage patterns are evaluated. Commercial wet electrodes are most commonly used for EIM. However, these electrodes are not suitable for use on small muscles, as they do not effectively solve the problem of high electrode-skin contact impedance (ESCI) that negatively influences the quality of recorded biopotentials. To address this problem, we fabricated a novel microneedle electrode array (MEA) that consists of 124-µm-long microneedles. Compared to wet electrodes, the MEA could pierce through the outer skin surface in a painless and micro-invasive manner, and could thus effectively reduce ESCI. The MEA has excellent test-retest reproducibility, with intraclass correlation coefficients exceeding 0.920. When used in combination with EIM, the MEA differentiated the affected muscles from the unaffected muscles in patients with neurogenic myopathy, by using EIM parameters of reactance and phase (p = 0.023 and 0.008, respectively). Thus, the novel MEA is a practical and reusable device for EIM assessment in cases of neurogenic myopathy. However, further refinement of the electrode is needed to enhance the clinical application of the system. PMID:26407702

  18. Guidelines to electrode positioning for human and animal electrical impedance myography research.

    PubMed

    Sanchez, Benjamin; Pacheck, Adam; Rutkove, Seward B

    2016-01-01

    The positioning of electrodes in electrical impedance myography (EIM) is critical for accurately assessing disease progression and effectiveness of treatment. In human and animal trials for neuromuscular disorders, inconsistent electrode positioning adds errors to the muscle impedance. Despite its importance, how the reproducibility of resistance and reactance, the two parameters that define EIM, are affected by changes in electrode positioning remains unknown. In this paper, we present a novel approach founded on biophysical principles to study the reproducibility of resistance and reactance to electrode misplacements. The analytical framework presented allows the user to quantify a priori the effect on the muscle resistance and reactance using only one parameter: the uncertainty placing the electrodes. We also provide quantitative data on the precision needed to position the electrodes and the minimum muscle length needed to achieve a pre-specified EIM reproducibility. The results reported here are confirmed with finite element model simulations and measurements on five healthy subjects. Ultimately, our data can serve as normative values to enhance the reliability of EIM as a biomarker and facilitate comparability of future human and animal studies. PMID:27585740

  19. Visualized Multiprobe Electrical Impedance Measurements with STM Tips Using Shear Force Feedback Control

    PubMed Central

    Botaya, Luis; Coromina, Xavier; Samitier, Josep; Puig-Vidal, Manel; Otero, Jorge

    2016-01-01

    Here we devise a multiprobe electrical measurement system based on quartz tuning forks (QTFs) and metallic tips capable of having full 3D control over the position of the probes. The system is based on the use of bent tungsten tips that are placed in mechanical contact (glue-free solution) with a QTF sensor. Shear forces acting in the probe are measured to control the tip-sample distance in the Z direction. Moreover, the tilting of the tip allows the visualization of the experiment under the optical microscope, allowing the coordination of the probes in X and Y directions. Meanwhile, the metallic tips are connected to a current–voltage amplifier circuit to measure the currents and thus the impedance of the studied samples. We discuss here the different aspects that must be addressed when conducting these multiprobe experiments, such as the amplitude of oscillation, shear force distance control, and wire tilting. Different results obtained in the measurement of calibration samples and microparticles are presented. They demonstrate the feasibility of the system to measure the impedance of the samples with a full 3D control on the position of the nanotips. PMID:27231911

  20. Decomposition method of an electrical bio-impedance signal into cardiac and respiratory components.

    PubMed

    Krivoshei, A; Kukk, V; Min, M

    2008-06-01

    The paper presents a method for adaptive decomposition of an electrical bio-impedance (BI) signal into two components: cardiac and respiratory. The decomposition of a BI signal is not a trivial process because of the non-stationarity of the signal components and overlapping of their harmonic spectra. An application specific orthonormal basis (ASOB) was designed to solve the decomposition task using the Jacobi weighting function in the standard Gram-Schmidt process. The key element of the bio-impedance signal decomposer (BISD) is a model of the cardiac BI signal, which is constructed from the components of the ASOB and is intended for use in the BISD for on-line tracking of the cardiac BI signal. It makes it possible to separate the cardiac and respiratory components of the total BI signal in non-stationary conditions. In combination with the signal-shape locked loop (SSLL), the BISD allows us to decompose the BI signals with partially overlapping spectra. The proposed BISD based method is accomplished as a PC software digital system, but it is oriented towards applications in portable and stationary cardiac devices and in clinical settings. PMID:18544800

  1. Visualized Multiprobe Electrical Impedance Measurements with STM Tips Using Shear Force Feedback Control.

    PubMed

    Botaya, Luis; Coromina, Xavier; Samitier, Josep; Puig-Vidal, Manel; Otero, Jorge

    2016-01-01

    Here we devise a multiprobe electrical measurement system based on quartz tuning forks (QTFs) and metallic tips capable of having full 3D control over the position of the probes. The system is based on the use of bent tungsten tips that are placed in mechanical contact (glue-free solution) with a QTF sensor. Shear forces acting in the probe are measured to control the tip-sample distance in the Z direction. Moreover, the tilting of the tip allows the visualization of the experiment under the optical microscope, allowing the coordination of the probes in X and Y directions. Meanwhile, the metallic tips are connected to a current-voltage amplifier circuit to measure the currents and thus the impedance of the studied samples. We discuss here the different aspects that must be addressed when conducting these multiprobe experiments, such as the amplitude of oscillation, shear force distance control, and wire tilting. Different results obtained in the measurement of calibration samples and microparticles are presented. They demonstrate the feasibility of the system to measure the impedance of the samples with a full 3D control on the position of the nanotips. PMID:27231911

  2. A new resonance-frequency based electrical impedance spectroscopy and its application in biomedical engineering

    NASA Astrophysics Data System (ADS)

    Dhurjaty, Sreeram; Qiu, Yuchen; Tan, Maxine; Zheng, Bin

    2014-03-01

    Electrical Impedance Spectroscopy (EIS) has shown promising results for differentiating between malignant and benign tumors, which exhibit different dielectric properties. However, the performance of current EIS systems has been inadequate and unacceptable in clinical practice. In the last several years, we have been developing and testing a new EIS approach using resonance frequencies for detection and classification of suspicious tumors. From this experience, we identified several limitations of current technologies and designed a new EIS system with a number of new characteristics that include (1) an increased A/D (analog-to-digital) sampling frequency, 24 bits, and a frequency resolution of 100 Hz, to increase detection sensitivity (2) automated calibration to monitor and correct variations in electronic components within the system, (3) temperature sensing and compensation algorithms to minimize impact of environmental change during testing, and (4) multiple inductor-switching to select optimum resonance frequencies. We performed a theoretical simulation to analyze the impact of adding these new functions for improving performance of the system. This system was also tested using phantoms filled with variety of liquids. The theoretical and experimental test results are consistent with each other. The experimental results demonstrated that this new EIS device possesses the improved sensitivity and/or signal detection resolution for detecting small impedance or capacitance variations. This provides the potential of applying this new EIS technology to different cancer detection and diagnosis tasks in the future.

  3. Guidelines to electrode positioning for human and animal electrical impedance myography research

    PubMed Central

    Sanchez, Benjamin; Pacheck, Adam; Rutkove, Seward B.

    2016-01-01

    The positioning of electrodes in electrical impedance myography (EIM) is critical for accurately assessing disease progression and effectiveness of treatment. In human and animal trials for neuromuscular disorders, inconsistent electrode positioning adds errors to the muscle impedance. Despite its importance, how the reproducibility of resistance and reactance, the two parameters that define EIM, are affected by changes in electrode positioning remains unknown. In this paper, we present a novel approach founded on biophysical principles to study the reproducibility of resistance and reactance to electrode misplacements. The analytical framework presented allows the user to quantify a priori the effect on the muscle resistance and reactance using only one parameter: the uncertainty placing the electrodes. We also provide quantitative data on the precision needed to position the electrodes and the minimum muscle length needed to achieve a pre-specified EIM reproducibility. The results reported here are confirmed with finite element model simulations and measurements on five healthy subjects. Ultimately, our data can serve as normative values to enhance the reliability of EIM as a biomarker and facilitate comparability of future human and animal studies. PMID:27585740

  4. A comparison of headnet electrode arrays for electrical impedance tomography of the human head.

    PubMed

    Tidswell, A T; Bagshaw, A P; Holder, D S; Yerworth, R J; Eadie, L; Murray, S; Morgan, L; Bayford, R H

    2003-05-01

    Three types of commercially available headnet electrode arrays, designed for use in EEG, and conventional EEG Ag/AgCl cup electrodes were tested on human subjects, and a realistic, saline-filled head-shaped tank was prepared with vegetable skin to simulate human skin in order to determine the optimum electrode system for electrical impedance tomography (EIT) of the human head. Impedance changes during EIT acquisition were produced in healthy volunteers during a finger-thumb apposition task and in tanks by the insertion of a Perspex rod. Signal-to-baseline noise, measured from raw EIT data, was 2.3 +/- 0.3 and 2.3 +/- 0.2 for the human and tank data, respectively. In both the human and tank experiments, a commercial hydrogel elasticated electrode headnet produced the least amount of baseline noise, and was the only headnet in the human data with noise levels acceptable for EIT imaging. Image quality measured in the tank was similar for most of the headnets tested, except that the EEG electrodes produced a higher positional error and electrodes in a geodesic elasticated net produced images with worse subjective image quality. Overall, the hydrogel elasticated headnet was judged to be the most suitable for human neuroimaging with EIT. PMID:12812436

  5. Optical Breast Shape Capture and Finite Element Mesh Generation for Electrical Impedance Tomography

    PubMed Central

    Forsyth, J.; Borsic, A.; Halter, R.J.; Hartov, A.; Paulsen, K.D.

    2011-01-01

    X-Ray mammography is the standard for breast cancer screening. The development of alternative imaging modalities is desirable because Mammograms expose patients to ionizing radiation. Electrical Impedance Tomography (EIT) may be used to determine tissue conductivity, a property which is an indicator of cancer presence. EIT is also a low-cost imaging solution and does not involve ionizing radiation. In breast EIT, impedance measurements are made using electrodes placed on the surface of the patient’s breast. The complex conductivity of the volume of the breast is estimated by a reconstruction algorithm. EIT reconstruction is a severely ill-posed inverse problem. As a result, noisy instrumentation and incorrect modelling of the electrodes and domain shape produce significant image artefacts. In this paper, we propose a method that has the potential to reduce these errors by accurately modelling the patient breast shape. A 3D hand-held optical scanner is used to acquire the breast geometry and electrode positions. We develop methods for processing the data from the scanner and producing volume meshes accurately matching the breast surface and electrode locations, which can be used for image reconstruction. We demonstrate this method for a plaster breast phantom and a human subject. Using this approach will allow patient-specific finite element meshes to be generated which has the potential to improve the clinical value of EIT for breast cancer diagnosis. PMID:21646711

  6. A Gold Sensors Array for Imaging The Real Tissue Phantom in Electrical Impedance Tomography

    NASA Astrophysics Data System (ADS)

    Kanti Bera, Tushar; Nagaraju, J.

    2015-02-01

    Surface electrodes in Electrical Impedance Tomography (EIT) phantoms usually reduce the SNR of the boundary potential data due to their design and development errors. A novel gold sensors array with high geometric precision is developed for EIT phantoms to improve the resistivity image quality. Gold thin films are deposited on a flexible FR4 sheet using electro-deposition process to make a sixteen electrode array with electrodes of identical geometry. A real tissue gold electrode phantom is developed with chicken tissue paste and the fat cylinders as the inhomogeneity. Boundary data are collected using a USB based high speed data acquisition system in a LabVIEW platform for different inhomogeneity positions. Resistivity images are reconstructed using EIDORS and compared with identical stainless steel electrode systems. Image contrast parameters are calculated from the resistivity matrix and the reconstructed images are evaluated for both the phantoms. Image contrast and image resolution of resistivity images are improved with gold electrode array.

  7. A generic screening platform for inhibitors of virus induced cell fusion using cellular electrical impedance

    PubMed Central

    Watterson, Daniel; Robinson, Jodie; Chappell, Keith J.; Butler, Mark S.; Edwards, David J.; Fry, Scott R.; Bermingham, Imogen M.; Cooper, Matthew A.; Young, Paul R.

    2016-01-01

    Fusion of the viral envelope with host cell membranes is an essential step in the life cycle of all enveloped viruses. Despite such a clear target for antiviral drug development, few anti-fusion drugs have progressed to market. One significant hurdle is the absence of a generic, high-throughput, reproducible fusion assay. Here we report that real time, label-free measurement of cellular electrical impedance can quantify cell-cell fusion mediated by either individually expressed recombinant viral fusion proteins, or native virus infection. We validated this approach for all three classes of viral fusion and demonstrated utility in quantifying fusion inhibition using antibodies and small molecule inhibitors specific for dengue virus and respiratory syncytial virus. PMID:26976324

  8. Electrical impedance spectroscopy device for measurement of moisture gradients in wood

    NASA Astrophysics Data System (ADS)

    Tiitta, M.; Olkkonen, H.

    2002-08-01

    A prototype of the electrical impedance spectroscopy (EIS) device for the measurement of internal moisture gradients in wood was developed. The EIS device consists of a hand-held probe connected to a control unit interfaced with a portable personal computer and a power unit. In the measurement, parallel flat electrodes of the measuring probe are laid against the wood specimen and the sine wave excitation is applied in the frequency range 1-100 kHz. The measured amplitude and phase spectral data were analyzed using the model based on constant phase elements. A spectral analysis software package was designed for measurement of subsurface transverse moisture gradients. The EIS device was tested with many types of uniform, desorption, and absorption gradients in lumber, pulpwood, and log specimens from spruce, pine, and birch. The EIS device can be easily transferred in a small case allowing field measurements.

  9. A generic screening platform for inhibitors of virus induced cell fusion using cellular electrical impedance.

    PubMed

    Watterson, Daniel; Robinson, Jodie; Chappell, Keith J; Butler, Mark S; Edwards, David J; Fry, Scott R; Bermingham, Imogen M; Cooper, Matthew A; Young, Paul R

    2016-01-01

    Fusion of the viral envelope with host cell membranes is an essential step in the life cycle of all enveloped viruses. Despite such a clear target for antiviral drug development, few anti-fusion drugs have progressed to market. One significant hurdle is the absence of a generic, high-throughput, reproducible fusion assay. Here we report that real time, label-free measurement of cellular electrical impedance can quantify cell-cell fusion mediated by either individually expressed recombinant viral fusion proteins, or native virus infection. We validated this approach for all three classes of viral fusion and demonstrated utility in quantifying fusion inhibition using antibodies and small molecule inhibitors specific for dengue virus and respiratory syncytial virus. PMID:26976324

  10. Generating anatomically accurate finite element meshes for electrical impedance tomography of the human head

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Xu, Canhua; Dai, Meng; Fu, Feng; Dong, Xiuzhen

    2013-07-01

    For electrical impedance tomography (EIT) of brain, the use of anatomically accurate and patient-specific finite element (FE) mesh has been shown to confer significant improvements in the quality of image reconstruction. But, given the lack of a rapid method to achieve the accurate anatomic geometry of the head, the generation of patient-specifc mesh is time-comsuming. In this paper, a modified fuzzy c-means algorithm based on non-local means method is performed to implement the segmentation of different layers in the head based on head CT images. This algorithm showed a better effect, especially an accurate recognition of the ventricles and a suitable performance dealing with noise. And the FE mesh established according to the segmentation results is validated in computational simulation. So a rapid practicable method can be provided for the generation of patient-specific FE mesh of the human head that is suitable for brain EIT.

  11. Expectation propagation for nonlinear inverse problems – with an application to electrical impedance tomography

    SciTech Connect

    Gehre, Matthias; Jin, Bangti

    2014-02-15

    In this paper, we study a fast approximate inference method based on expectation propagation for exploring the posterior probability distribution arising from the Bayesian formulation of nonlinear inverse problems. It is capable of efficiently delivering reliable estimates of the posterior mean and covariance, thereby providing an inverse solution together with quantified uncertainties. Some theoretical properties of the iterative algorithm are discussed, and the efficient implementation for an important class of problems of projection type is described. The method is illustrated with one typical nonlinear inverse problem, electrical impedance tomography with complete electrode model, under sparsity constraints. Numerical results for real experimental data are presented, and compared with that by Markov chain Monte Carlo. The results indicate that the method is accurate and computationally very efficient.

  12. Simultaneous recovery of admittivity and body shape in electrical impedance tomography: an experimental evaluation

    NASA Astrophysics Data System (ADS)

    Dardé, Jérémi; Hyvönen, Nuutti; Seppänen, Aku; Staboulis, Stratos

    2013-08-01

    In this paper, the simultaneous retrieval of the exterior boundary shape and the interior admittivity distribution of an examined body in electrical impedance tomography is considered. The reconstruction method is built for the complete electrode model and it is based on the Fréchet derivative of the corresponding current-to-voltage map with respect to the body shape. The reconstruction problem is cast into the Bayesian framework, and maximum a posteriori estimates for the admittivity and the boundary geometry are computed. The feasibility of the approach is evaluated by experimental data from water tank measurements. The results demonstrate that the proposed method has potential for handling an unknown body shape in a practical setting.

  13. The sensor of surface defects based on electrical impedance tomography technique

    NASA Astrophysics Data System (ADS)

    Ryndin, Eugeny A.; Isaeva, Alina S.

    2014-12-01

    This paper describes the application of electrical impedance tomography (EIT) to development of the surface defect sensor that can be used for structural health monitoring (such structural as bridge bearing, airframe, etc.). Thin conductive film with electrodes along its boundaries, as a sensor skin, is applied to structural surface. By using the corresponding boundary potential measurements and the value of applied current the both forward and inverse EIT problem were solved and method of defects detection in thin conductive film was created. This method allows calculating two-dimensional distribution of conductivity in film (conductivity map) and, indirectly, distribution of defects in it. The reconstruction defect efficiency criterion and the method of its calculation were proposed. The influence of initial data disturbance (non-uniform conductivity of the film as its roughness) on reconstruction defect efficiency without using all the combinations of current electrodes was examined.

  14. Nonstationary phase boundary estimation in electrical impedance tomography using unscented Kalman filter

    SciTech Connect

    Ijaz, Umer Zeeshan; Khambampati, Anil Kumar; Lee, Jeong Seong; Kim, Sin; Kim, Kyung Youn

    2008-07-20

    In this paper, an effective nonstationary phase boundary estimation scheme in electrical impedance tomography is presented based on the unscented Kalman filter. The inverse problem is treated as a stochastic nonlinear state estimation problem with the nonstationary phase boundary (state) being estimated online with the aid of unscented Kalman filter. This research targets the industrial applications, such as imaging of stirrer vessel for detection of air distribution or detecting large air bubbles in pipelines. Within the domains, there exist 'voids' having zero conductivity. The design variables for phase boundary estimation are truncated Fourier coefficients. Computer simulations and experimental results are provided to evaluate the performance of unscented Kalman filter in comparison with extended Kalman filter to show a better performance of the unscented Kalman filter approach.

  15. Applications of GRID in clinical neurophysiology and Electrical Impedance Tomography of brain function.

    PubMed

    Fritschy, J; Horesh, L; Holder, D; Bayford, R

    2005-01-01

    The computational requirements in Neurophysiology are increasing with the development of new analysis methods. The resources the GRID has to offer are ideally suited for this complex processing. A practical implementation of the GRID, Condor, has been assessed using a local cluster of 920 PCs. The reduction in processing time was assessed in spike recognition of the Electroencephalogram (EEG) in epilepsy using wavelets and the computationally demanding task of non-linear image reconstruction with Electrical Impedance Tomography (EIT). Processing times were decreased by 25 and 40 times respectively. This represents a substantial improvement in processing time, but is still sub optimal due to factors such as shared access to resources and lack of checkpoints so that interrupted jobs had to be restarted. Future work will be to use these methods in non-linear EIT image reconstruction of brain function and methods for automated EEG analysis, if possible with further optimized GRID middleware. PMID:15923723

  16. Biological impedance cross evaluation and imaging from composite measurements of magnetic and electrical methods.

    PubMed

    Ran, Peng; Xiao, Xiaoming; He, Wei; Li, Zhangyong

    2015-01-01

    Because of the need for rapid detection and location of diseases in clinical applications, this work proposes a composite measurement of magnetic induction tomography (MIT) and electrical impedance tomography (EIT). This paper is composed of the following aspects: portable and integral hardware design, stable dual constant-current sources, the composite detection method, cross-plane data acquirement, 3-dimensional image reconstruction and so on. A qualitative evaluation of conductivity, resolution and relative position error were taken by combining the EIT and MIT methods via the experiment model. The sensitivities of both methods were analyzed to improve the imaging results. The reconstruction results reveal that the system is capable of obtaining better physiological measurements, which is very useful in clinical monitoring, quick medical diagnosing and preliminary screening of community health. PMID:26405936

  17. SU-E-I-52: Validation of Multi-Frequency Electrical Impedance Tomography Using Computed Tomography

    SciTech Connect

    Kohli, K; Liu, F; Krishnan, K

    2014-06-01

    Purpose: Multi-frequency EIT has been reported to be a potential tool in distinguishing a tissue anomaly from background. In this study, we investigate the feasibility of acquiring functional information by comparing multi-frequency EIT images in reference to the structural information from the CT image through fusion. Methods: EIT data was acquired from a slice of winter melon using sixteen electrodes around the phantom, injecting a current of 0.4mA at 100, 66, 24.8 and 9.9 kHz. Differential EIT images were generated by considering different combinations of pair frequencies, one serving as reference data and the other as test data. The experiment was repeated after creating an anomaly in the form of an off-centered cavity of diameter 4.5 cm inside the melon. All EIT images were reconstructed using Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS) package in 2-D differential imaging mode using one-step Gaussian Newton minimization solver. CT image of the melon was obtained using a Phillips CT Scanner. A segmented binary mask image was generated based on the reference electrode position and the CT image to define the regions of interest. The region selected by the user was fused with the CT image through logical indexing. Results: Differential images based on the reference and test signal frequencies were reconstructed from EIT data. Result illustrated distinct structural inhomogeneity in seeded region compared to fruit flesh. The seeded region was seen as a higherimpedance region if the test frequency was lower than the base frequency in the differential EIT reconstruction. When the test frequency was higher than the base frequency, the signal experienced less electrical impedance in the seeded region during the EIT data acquisition. Conclusion: Frequency-based differential EIT imaging can be explored to provide additional functional information along with structural information from CT for identifying different tissues.

  18. Assessing risk of thyroid cancer using resonance-frequency based electrical impedance measurements

    NASA Astrophysics Data System (ADS)

    Zheng, Bin; Tublin, Mitchell E.; Lederman, Dror; Klym, Amy H.; Brown, Erica D.; Gur, David

    2011-03-01

    The incidence of thyroid cancer has risen faster than many malignancies and has nearly doubled in the USA over the past 30 years. Palpable nodules and subclinical nodules detected by imaging are found in a large percentage of the USA population. Most of these (.>95%) are fortunately benign. This vast reservoir of nodules makes the detection and diagnosis of thyroid cancer a diagnostic dilemma. Ultrasound guided Fine Needle Aspiration Biopsy (FNAB) is excellent for triaging patients but up to 25% of FNABs are inconclusive. As a result, definitive diagnosis is often only possible with a diagnostic lobectomy; many thousands of these are performed in the USA annually for ultimately benign disease. It would be extremely beneficial if we could develop a non-invasive procedure that could assist the diagnostician in reliably predicting the likelihood of malignancy of otherwise indeterminate thyroid nodules, thereby reducing the number of these "exploratory/diagnostic" lobectomies performed under general anesthesia. Electrical Impedance Spectroscopy (EIS) was considered as a possible approach to address this problem. However, the diagnostic accuracy of EIS is too low for routine clinical use to date. In our group, we developed a substantially modified technology termed Resonance-frequency Electrical Impedance Spectroscopy (REIS), which yields usable information for classifying risk of having breast abnormalities. We preliminarily applied REIS to measure signals on participants having thyroid nodules aiming to assess whether we can assist in improving diagnosis of indeterminate thyroid nodules. In this study we present a new multi-probe based REIS device specifically designed for the assessment of indeterminate thyroid nodules. Our preliminary assessment presented here demonstrates the feasibility of using this proposed REIS device in a busy tertiary care center.

  19. Electrical Impedance Tomography-guided PEEP Titration in Patients Undergoing Laparoscopic Abdominal Surgery.

    PubMed

    He, Xingying; Jiang, Jingjing; Liu, Yuli; Xu, Haitao; Zhou, Shuangqiong; Yang, Shibo; Shi, Xueyin; Yuan, Hongbin

    2016-04-01

    The aim of the study is to utilize electrical impedance tomography (EIT) to guide positive end-expiratory pressure (PEEP) and to optimize oxygenation in patients undergoing laparoscopic abdominal surgery.Fifty patients were randomly assigned to the control (C) group and the EIT (E) group (n = 25 each). We set the fraction of inspired oxygen (FiO2) at 0.30. The PEEP was titrated and increased in a 2-cm H2O stepwise manner, from 6 to 14 cm H2O. Hemodynamic variables, respiratory mechanics, EIT images, analysis of blood gas, and regional cerebral oxygen saturation were recorded. The postoperative pulmonary complications within the first 5 days were also observed.We chose 10 cm H2O and 8 cm H2O as the "ideal" PEEP for the C and the E groups, respectively. EIT-guided PEEP titration led to a more dorsal shift of ventilation. The PaO2/FiO2 ratio in the E group was superior to that in the C group in the pneumoperitoneum period, though the difference was not significant (330 ± 10 vs 305.56 ± 4 mm Hg; P = 0.09). The C group patients experienced 8.7% postoperative pulmonary complications versus 5.3% among the E group patients (relative risk 1.27, 95% confidence interval 0.31-5.3, P = 0.75).Electrical impedance tomography represents a new promising technique that could enable anesthesiologists to assess regional ventilation of the lungs and optimize global oxygenation for patients undergoing laparoscopic abdominal surgery. PMID:27057904

  20. Sensitivity study of an ultrasound coupled transrectal electrical Impedance Tomography system for prostate imaging

    NASA Astrophysics Data System (ADS)

    Wan, Y.; Halter, R.; Borsic, A.; Manwaring, P.; Hartov, A.; Paulsen, K.

    2010-04-01

    In 2009, prostate cancer ranks as the most common cancer and the second most fatal cancer in men in the United States. Unfortunately, the current clinical diagnostic methods (e.g. prostate-specific antigen (PSA), digital rectal examination, endorectal MRI, transrectal ultrasound, biopsy) used for detecting and staging prostate cancer are limited. It has been shown that cancerous prostate tissue has significantly different electrical properties when compared to benign tissues. Based on these electrical property findings, a TransRectal Electrical Impedance Tomography (TREIT) system is proposed as a novel prostate imaging modality. The TREIT system is comprised of an array of electrodes interfaced with a clinical TransRectal UltraSound (TRUS) probe. We evaluate this imaging system through series of phantom imaging experiments to assess the system's ability to image high and low contrast objects at various positions. We found that the TREIT system can easily discern high contrast inclusions of 1 cm in diameter at distances centered at 2 times the radius of the TREIT probe away from the probe surface. Furthermore, this technology's ability to detect low contrast inclusions suggests that it has the potential to successfully detect prostate cancer.

  1. Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

    2015-03-01

    Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as Bz. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple Bz data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured Bz data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

  2. Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

    SciTech Connect

    Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Woo, Eung Je; Kwon, Oh In

    2015-03-14

    Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as B{sub z}. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple B{sub z} data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured B{sub z} data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

  3. Electrically scanning microwave radiometers. [for satellite-borne remote sensing

    NASA Technical Reports Server (NTRS)

    Mix, R. F.

    1974-01-01

    The electrically scanning microwave radiometer (ESMR) developed for and currently used onboard the Nimbus 5 meteorological satellite is described, along with the ESMR developed for the Nimbus F satellite. They serve for synoptic mapping of microwave emissions from the earth's surface, the instrument on Nimbus 5 measuring these emissions at a wavelength of 1.55 cm (19.35 GHz) and the instrument on Nimbus F, at a wavelength of 0.81 cm (37 GHz). Radiative transfer characteristics measured at these wavelengths are sufficiently different from IR measurements to permit derivation and interpretation of unique meteorological, geomorphological, and oceanographic data.

  4. Noise analysis in fast magnetic resonance electrical impedance tomography (MREIT) based on spoiled multi gradient echo (SPMGE) pulse sequence

    NASA Astrophysics Data System (ADS)

    In Oh, Tong; Jeong, Woo Chul; Kim, Ji Eun; Sajib, Saurav Z. K.; Kim, Hyung Joong; In Kwon, Oh; Woo, Eung Je

    2014-08-01

    Magnetic resonance electrical impedance tomography (MREIT) is a promising non-invasive method to visualize a static cross-sectional conductivity and/or current density image by injecting low frequency currents. MREIT measures one component of the magnetic flux density caused by the injected current using a magnetic resonance (MR) scanner. For practical in vivo implementations of MREIT, especially for soft biological tissues where the MR signal rapidly decays, it is crucial to develop a technique for optimizing the magnetic flux density signal by the injected current while maintaining spatial-resolution and contrast. We design an MREIT pulse sequence by applying a spoiled multi-gradient-echo pulse sequence (SPMGE) to the injected current nonlinear encoding (ICNE), which fully injects the current at the end of the read-out gradient. The applied ICNE-SPMGE pulse sequence maximizes the duration of injected current almost up to a repetition time by measuring multiple magnetic flux density data. We analyze the noise level of measured magnetic flux density with respect to the pulse width of injection current and T_{2}^{*} relaxation time. In due consideration of the ICNE-SPMGE pulse sequence, using a reference information of T_{2}^{*} values in a local region of interest by a short pre-scan data, we predict the noise level of magnetic flux density to be measured for arbitrary repetition time TR. Results from phantom experiment demonstrate that the proposed method can predict the noise level of magnetic flux density for an appropriate TR = 40 ms using a reference scan for TR = 75 ms. The predicted noise level was compared with the noise level of directly measured magnetic flux density data.

  5. Transoesophageal detection of heart graft rejection by electrical impedance: Using finite element method simulations

    NASA Astrophysics Data System (ADS)

    Giovinazzo, G.; Ribas, N.; Cinca, J.; Rosell-Ferrer, J.

    2010-04-01

    Previous studies have shown that it is possible to evaluate heart graft rejection level using a bioimpedance technique by means of an intracavitary catheter. However, this technique does not present relevant advantages compared to the gold standard for the detection of a heart rejection, which is the biopsy of the endomyocardial tissue. We propose to use a less invasive technique that consists in the use of a transoesophageal catheter and two standard ECG electrodes on the thorax. The aim of this work is to evaluate different parameters affecting the impedance measurement, including: sensitivity to electrical conductivity and permittivity of different organs in the thorax, lung edema and pleural water. From these results, we deduce the best estimator for cardiac rejection detection, and we obtain the tools to identify possible cases of false positive of heart rejection due to other factors. To achieve these objectives we have created a thoracic model and we have simulated, with a FEM program, different situations at the frequencies of 13, 30, 100, 300 and 1000 kHz. Our simulation demonstrates that the phase, at 100 and 300 kHz, has the higher sensitivity to changes in the electrical parameters of the heart muscle.

  6. A Robust Current Pattern for the Detection of Intraventricular Hemorrhage in Neonates Using Electrical Impedance Tomography

    PubMed Central

    Tang, T.; Oh, Sungho; Sadleir, R. J.

    2010-01-01

    We compared two 16-electrode electrical impedance tomography (EIT) current patterns on their ability to reconstruct and quantify small amounts of bleeding inside a neonatal human head using both simulated and phantom data. The current patterns used were an adjacent injection RING pattern (with electrodes located equidistantly on the equator of a sphere) and an EEG current pattern based on the 10–20 EEG electrode layout. Structures mimicking electrically important structures in the infant skull were included in a spherical numerical forward model and their effects on reconstructions were determined. The EEG pattern was found to be a better topology to localize and quantify anomalies within lateral ventricular regions. The RING electrode pattern could not reconstruct anomaly location well, as it could not distinguish different axial positions. The quantification accuracy of the RING pattern was as good as the EEG pattern in noise-free environments. However, the EEG pattern showed better quantification ability than the RING pattern when noise was added. The performance of the EEG pattern improved further with respect to the RING pattern when a fontanel was included in forward models. Significantly better resolution and contrast of reconstructed anomalies was achieved when generated from a model containing such an opening and 50 dB added noise. The EEG method was further applied to reconstruct data from a realistic neonatal head model. Overall, acceptable reconstructions and quantification results were obtained using this model and the homogeneous spherical forward model. PMID:20238166

  7. Nanoparticle-enhanced electrical impedance detection and its potential significance in image tomography

    PubMed Central

    Liu, Ran; Jin, Cuiyun; Song, Fengjuan; Liu, Jing

    2013-01-01

    The conductivity and permittivity of tumors are known to differ significantly from those of normal tissues. Electrical impedance tomography (EIT) is a relatively new imaging method for exploiting these differences. However, the accuracy of data capture is one of the difficult problems urgently to be solved in the clinical application of EIT technology. A new concept of EIT sensitizers is put forward in this paper with the goal of expanding the contrast ratio of tumor and healthy tissue to enhance EIT imaging quality. The use of nanoparticles for changing tumor characteristics and determining the infiltration vector for easier detection has been widely accepted in the biomedical field. Ultra-pure water, normal saline, and gold nanoparticles, three kinds of material with large differences in electrical characteristics, are considered as sensitizers and undergo mathematical model analysis and animal experimentation. Our preliminary results suggest that nanoparticles are promising for sensitization work. Furthermore, in experimental and simulation results, we found that we should select different sensitizers for the detection of different types and stages of tumor. PMID:23319858

  8. An electric impedance based microelectromechanical system flow sensor for ionic solutions

    PubMed Central

    Ayliffe, H Edward; Rabbitt, RD

    2008-01-01

    Microfluidic devices with channel cross sections measuring 4 × 10 μm2 instrumented with gold microelectrodes were used to sense flow rates of ionic solutions on the basis of electric impedance (EI) measured perpendicular to the flow. Negative pressures were applied to access ports of the microdevices to generate flow of saline solutions (physiologic concentrations 0.9%) through the micro-EI recording zone with flow rates between 2.4 and 4.8 μl min−1. The EI spectra (100 Hz–20 MHz) recorded under flow conditions were compared with the no-flow condition. Changes in the magnitude of EI (at 350 Hz) for flow rates as low as 2.4 μl min−1 were statistically significant compared with the no-flow condition. The observed dependence of EI on flow rate is attributed to the relative difference between the rate of migration of charge-balancing electrolyte ions to the electrode surface and the rate of removal of the same ions by forced convection. An electrochemical convection–diffusion model was used to study the observed dependence on flow. Simulations support the conceptual model that passing DC current from the gold electrodes into the ionic solution results in an increase in ionic concentration near the electrode surface (due to the inward migration of counter-balancing ions). When the fluid flow rates increase, these counter-balancing ions are replaced by the bulk solution, thereby lowering the average ionic concentration within the recording zone. This local concentration drop results in an increase in the real part of the impedance. PMID:19672321

  9. Electrical impedance myography to assess outcome in amyotrophic lateral sclerosis clinical trials

    PubMed Central

    Rutkove, Seward B.; Zhang, Hui; Schoenfeld, David A.; Raynor, Elizabeth M.; Shefner, Jeremy M.; Cudkowicz, Merit E.; Chin, Anne B.; Aaron, Ronald; Shiffman, Carl A.

    2007-01-01

    Objective Standard outcome measures used for amyotrophic lateral sclerosis (ALS) clinical trials, including the ALS Functional Rating Scale-revised (ALSFRS-R), maximal voluntary isometric contraction testing (MVICT), and manual muscle testing (MMT) are limited in their ability to detect subtle disease progression. Electrical impedance myography (EIM) is a new non-invasive technique that provides quantitative data on muscle health by measuring localized tissue impedance. This study investigates whether EIM could provide a new outcome measure for use in ALS clinical trials work. Methods Fifteen ALS patients underwent repeated EIM measurements of one or more muscles over a period of up to 18 months and the primary outcome variable, θz-max, measured. The θz-max megascore was then calculated using the same approach as has been applied in the past for MVICT. This and the MMT data were then used to assess each measure’s statistical power to detect a given effect on disease progression in a hypothetical planned clinical therapeutic trial. Results θz-max showed a mean decline of about 21% for the test period, averaged across all patients and all tested muscles. The θz-max megascore had a power of 73% to detect a 10% treatment effect in our planned hypothetical trial, as compared to a 28% power for MMT. These results also compared favorably to historical data for ALSFRS-R and MVICT arm megascore from the trial of celecoxib in ALS, where both measures had only a 23% power to detect the same 10% treatment effect. Conclusions The θz-max megascore may provide a powerful new outcome measure for ALS clinical trials. Significance The application of EIM to future ALS trials may allow for smaller, faster studies with an improved ability to detect subtle treatment effects. PMID:17897874

  10. Left and right preconditioning for electrical impedance tomography with structural information

    NASA Astrophysics Data System (ADS)

    Calvetti, Daniela; McGivney, Debra; Somersalo, Erkki

    2012-05-01

    A common problem in computational inverse problems is to find an efficient way of solving linear or nonlinear least-squares problems. For large-scale problems, iterative solvers are the method of choice for solving the associated linear systems, and for nonlinear problems, an additional effective local linearization method is required. In this paper, we discuss an efficient preconditioning scheme for Krylov subspace methods, based on the Bayesian analysis of the inverse problem. The model problem to which we apply this methodology is electrical impedance tomography (EIT) augmented with prior information coming from a complementary modality, such as x-ray imaging. The particular geometry considered here models the x-ray-guided EIT for breast imaging. The interest in applying EIT concurrently with x-ray breast imaging arises from the experimental observation that the impedivity spectra of certain types of malignant and benign tissues differ significantly from each other, thus offering a possibility of diagnosis without more invasive tissue sampling. After setting up the EIT inverse problem within a Bayesian framework, we present an inner and outer iteration scheme for computing a maximum a posteriori estimate. The prior covariance provides a right preconditioner and the modeling error covariance provides a left preconditioner for the iterative method used to solve the linear least-squares problem at each outer iteration of the optimization problem. Moreover, the stopping criterion for the inner iterations is coupled with the progress of the solution of the outer iteration. Besides the preconditioning scheme, the computational efficiency relies on a very efficient method to compute the Jacobian, obtained by carefully organizing the forward computation. Computed examples illustrate the robustness and computational efficiency of the proposed algorithm.

  11. Sub-millimeter resolution electrical conductivity images of brain tissues using magnetic resonance-based electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Oh, Tong In; Kim, Hyun Bum; Jeong, Woo Chul; Sajib, Saurav Z. K.; Kyung, Eun Jung; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

    2015-07-01

    Recent magnetic resonance (MR)-based electrical impedance tomography (MREIT) of in vivo animal and human subjects enabled the imaging of electromagnetic properties, such as conductivity and permittivity, on tissue structure and function with a few millimeter pixel size. At those resolutions, the conductivity contrast might be sufficient to distinguish different tissue type for certain applications. Since the precise measurement of electrical conductivity under the tissue levels can provide alternative information in a wide range of biomedical applications, it is necessary to develop high-resolution MREIT technique to enhance its availability. In this study, we provide the experimental evaluation of sub-millimeter resolution conductivity imaging method using a 3T MR scanner combined with a multi-echo MR pulse sequence, multi-channel RF coil, and phase optimization method. From the phantom and animal imaging results, sub-millimeter resolution exhibited similar signal-to-noise ratio of MR magnitude and noise levels in magnetic flux density comparing to the existing millimeter resolution. The reconstructed conductivity images at sub-millimeter resolution can distinguish different brain tissues with a pixel size as small as 350 μm.

  12. Sub-millimeter resolution electrical conductivity images of brain tissues using magnetic resonance-based electrical impedance tomography

    SciTech Connect

    Oh, Tong In; Jeong, Woo Chul; Sajib, Saurav Z. K.; Kim, Hyung Joong Woo, Eung Je; Kim, Hyun Bum; Kyung, Eun Jung; Kwon, Oh In

    2015-07-13

    Recent magnetic resonance (MR)-based electrical impedance tomography (MREIT) of in vivo animal and human subjects enabled the imaging of electromagnetic properties, such as conductivity and permittivity, on tissue structure and function with a few millimeter pixel size. At those resolutions, the conductivity contrast might be sufficient to distinguish different tissue type for certain applications. Since the precise measurement of electrical conductivity under the tissue levels can provide alternative information in a wide range of biomedical applications, it is necessary to develop high-resolution MREIT technique to enhance its availability. In this study, we provide the experimental evaluation of sub-millimeter resolution conductivity imaging method using a 3T MR scanner combined with a multi-echo MR pulse sequence, multi-channel RF coil, and phase optimization method. From the phantom and animal imaging results, sub-millimeter resolution exhibited similar signal-to-noise ratio of MR magnitude and noise levels in magnetic flux density comparing to the existing millimeter resolution. The reconstructed conductivity images at sub-millimeter resolution can distinguish different brain tissues with a pixel size as small as 350 μm.

  13. Impedance measurements on lead-acid batteries for state-of-charge, state-of-health and cranking capability prognosis in electric and hybrid electric vehicles

    NASA Astrophysics Data System (ADS)

    Blanke, Holger; Bohlen, Oliver; Buller, Stephan; De Doncker, Rik W.; Fricke, Birger; Hammouche, Abderrezak; Linzen, Dirk; Thele, Marc; Sauer, Dirk Uwe

    Various attempts have been made to use impedance measurements for online analysis and offline modelling of lead-acid batteries. This presentation gives an overview on the latest and successful approaches based on impedance measurements to assess state-of-charge (SoC), state-of-health (SoH) and cranking capability of lead-acid batteries. Furthermore, it is shown that impedance data can serve as a basis for dynamic battery models for the simulation of vehicle power-supply systems. The methods and procedures aim for a reliable prediction of battery performance in electric vehicles, hybrid cars and classical automotive applications. Although, it will become obvious that impedance measurements give valuable information on the battery state, typically the information needs to be combined with other conventional algorithms or self-learning tools to achieve reliable and stable results for real-world applications.

  14. Effect of psychological stress on gastric motility assessed by electrical bio-impedance

    PubMed Central

    Huerta-Franco, María Raquel; Vargas-Luna, Miguel; Montes-Frausto, Juana Berenice; Morales-Mata, Ismael; Ramirez-Padilla, Lorena

    2012-01-01

    AIM: To evaluate gastric motility using electrical bio-impedance (EBI) and gastric changes as a result of stress induced by psychological tests. METHODS: A group of 57 healthy women, aged 40-60 years, was recruited, and a clinical history and physical examination were performed. The women were free from severe anxiety, chronic or acute stress, severe depression, mental diseases and conditions that affect gastric activity. The women were evaluated under fasting conditions, and using a four-electrode configuration, the gastric signals were obtained through a BIOPAC MP-150 system. The volunteers were evaluated using the following paradigm: basal state, recording during the Stroop Test, intermediate resting period, recording during the Raven Test, and a final resting period. We analyzed the relative areas of the frequency spectrum: A1 (1-2 cpm), A2 (2-4 cpm), A3 (4-8 cpm), and A4 (8-12 cpm), as well as the median of area A2 + A3. The data were analyzed by an autoregressive method using a Butterworth filter with MatLab and Origin. Analysis of variance (ANOVA) and Friedman ANOVA (for nonparametric variables) were performed; in addition, pairs of groups were compared using the T dependent and Wilcoxon T tests. RESULTS: The results of the main values of area A2 were not significantly different comparing the five steps of the experimental paradigm. Nevertheless, there was a tendency of this A2 region to decrease during the stress tests, with recuperation at the final resting step. When an extended gastric region was considered (1-4 cpm), significant differences with the psychological stress tests were present (F = 3.85, P = 0.005). The A3 region also showed significant changes when the stress psychological tests were administered (F = 7.25, P < 0.001). These differences were influenced by the changes in the adjacent gastric region of A2. The parameter that we proposed in previous studies for the evaluation of gastric motility by electrical bio-impedance (EBI) was the median

  15. Assembling a prototype resonance electrical impedance spectroscopy system for breast tissue signal detection: preliminary assessment

    NASA Astrophysics Data System (ADS)

    Sumkin, Jules; Zheng, Bin; Gruss, Michelle; Drescher, John; Leader, Joseph; Good, Walter; Lu, Amy; Cohen, Cathy; Shah, Ratan; Zuley, Margarita; Gur, David

    2008-03-01

    Using electrical impedance spectroscopy (EIS) technology to detect breast abnormalities in general and cancer in particular has been attracting research interests for decades. Large clinical tests suggest that current EIS systems can achieve high specificity (>= 90%) at a relatively low sensitivity ranging from 15% to 35%. In this study, we explore a new resonance frequency based electrical impedance spectroscopy (REIS) technology to measure breast tissue EIS signals in vivo, which aims to be more sensitive to small tissue changes. Through collaboration between our imaging research group and a commercial company, a unique prototype REIS system has been assembled and preliminary signal acquisition has commenced. This REIS system has two detection probes mounted in the two ends of a Y-shape support device with probe separation of 60 mm. During REIS measurement, one probe touches the nipple and the other touches to an outer point of the breast. The electronic system continuously generates sweeps of multi-frequency electrical pulses ranging from 100 to 4100 kHz. The maximum electric voltage and the current applied to the probes are 1.5V and 30mA, respectively. Once a "record" command is entered, multi-frequency sweeps are recorded every 12 seconds until the program receives a "stop recording" command. In our imaging center, we have collected REIS measurements from 150 women under an IRB approved protocol. The database includes 58 biopsy cases, 78 screening negative cases, and other "recalled" cases (for additional imaging procedures). We measured eight signal features from the effective REIS sweep of each breast. We applied a multi-feature based artificial neural network (ANN) to classify between "biopsy" and normal "non-biopsy" breasts. The ANN performance is evaluated using a leave-one-out validation method and ROC analysis. We conducted two experiments. The first experiment attempted to classify 58 "biopsy" breasts and 58 "non-biopsy" breasts acquired on 58 women

  16. Development of a combined ultrasound and electrical impedance imaging system for prostate cancer detection

    NASA Astrophysics Data System (ADS)

    Wan, Yuqing

    Approximately 240,890 men were diagnosed with prostate cancer and 33,720 men were expected to die from it in the year of 2011 in the United States. Unfortunately, the current clinical diagnostic methods (e.g. prostate-specific antigen (PSA), digital rectal examination, ultrasound guided biopsy) used for detecting and staging prostate cancer are limited. It has been shown that cancerous prostate tissue has significantly different electrical properties when compared to benign tissues. Based on these electrical property findings, a transrectal electrical impedance tomography (TREIT) system is proposed as a novel prostate imaging modality. An ultrasound probe is incorporated with TREIT to achieve anatomic information of the prostate and guide electrical property reconstruction. Without the guidance of the ultrasound, the TREIT system can easily discern high contrast inclusions of 1 cm in diameter at distances centered at two times the radius of the TREIT probe away from the probe surface. Furthermore, we have demonstrated that our system is able to detect low contrast inclusions. With the guidance of the ultrasound, our system is capable of detecting a plastic inclusion embedded in a gelatin phantom, indicating the potential to detect cancer. In addition, the results of preliminary in vivo clinical trials using the imaging system are also presented in the thesis. After collecting data for a total 66 patients, we demonstrated that the in vivo conductivity of cancerous tissue is significantly greater than that of benign tissue (p=0.0015 at 400 Hz) and the conductivity of BPH tissue is significantly lower than that of normal tissue (p=0.0009 at 400 Hz). Additionally at 25.6 kHz, the dual-modal imaging system is able to differentiate cancerous tissue from benign tissue with sensitivity of 0.6012 and specificity of 0.5498, normal tissue from BPH tissue with sensitivity of 0.6085 and specificity of 0.5813 and differentiate cancerous tissue from BPH tissue with sensitivity of

  17. Ex vivo characterization of age-associated impedance changes of single vascular endothelial cells using micro electrical impedance spectroscopy with a cell trap.

    PubMed

    Park, Yangkyu; Cha, Jung-Joon; Seo, Seungwan; Yun, Joho; Woo Kim, Hyeon; Park, Changju; Gang, Giseok; Lim, Juhun; Lee, Jong-Hyun

    2016-01-01

    We aimed to characterize aging of single vascular endothelial cells, which are indicators of senescence, using micro electrical impedance spectroscopy (μEIS) for the first time. The proposed μEIS was equipped with two barriers under the membrane actuator near the sensing electrodes, increasing its cell-trapping capability and minimizing the interference between the target cell and subsequent cells. The cell-trapping capability in μEIS with barriers was considerably improved (90%) with a capture time of 5 s or less, compared to μEIS without barriers (30%). Cells were extracted from transgenic zebrafish to minimize an initial discrepancy originating from genetic differences. In order to estimate useful parameters, cytoplasm resistance and membrane capacitance were estimated by fitting an electrical equivalent circuit to the data of ex vivo sensor output. The estimated cytoplasm resistance and membrane capacitance in the younger vascular endothelial cells were 20.16 ± 0.79 kΩ and 17.46 ± 0.76 pF, respectively, whereas those in the older cells were 17.81 ± 0.98 kΩ and 20.08 ± 1.38 pF, respectively. Discrimination of each group with different aging showed statistical significance in terms of cytoplasm resistance (p < 0.001) and membrane capacitance (p < 0.001). Considering both of the sensor and cellular level, the optimal frequency was determined as 1 MHz at which the electrical impedance of each group was clearly discriminated (p < 0.001). PMID:26865907

  18. Cost-effective broad-band electrical impedance spectroscopy measurement circuit and signal analysis for piezo-materials and ultrasound transducers.

    PubMed

    Lewis, George K; Lewis, George K; Olbricht, William

    2008-10-01

    This paper explains the circuitry and signal processing to perform electrical impedance spectroscopy on piezoelectric materials and ultrasound transducers. Here, we measure and compare the impedance spectra of 2-5 MHz piezoelectrics, but the methodology applies for 700 kHz-20 MHz ultrasonic devices as well. Using a 12 ns wide 5 volt pulsing circuit as an impulse, we determine the electrical impedance curves experimentally using Ohm's law and fast Fourier transform (FFT), and compare results with mathematical models. The method allows for rapid impedance measurement for a range of frequencies using a narrow input pulse, digital oscilloscope and FFT techniques. The technique compares well to current methodologies such as network and impedance analyzers while providing additional versatility in the electrical impedance measurement. The technique is theoretically simple, easy to implement and completed with ordinary laboratory instrumentation for minimal cost. PMID:19081773

  19. Visualization of the meridian of traditional Chinese medicine with electrical impedance tomography: An initial experience

    NASA Astrophysics Data System (ADS)

    Cao, Yanli; Lu, Xiaozuo; Wang, Xuemin

    2010-04-01

    The meridian is a concept central to traditional Chinese medical techniques such as acupuncture. There is no physically verifiable anatomical or histological basis for the existence of meridians. In Chinese medicine, the meridians are channels along which the energy of the psychological system is considered to flow. It has been proven that the resistance along the meridian channels is lower compared to other paths. Based on this knowledge, we proposed using electrical impedance tomography (EIT) to visualize the meridians of human being. A simplified three dimensional (3D) mathematical model of the forearm developed. Current was injected in the direction perpendicular to the cross-section where eight electrodes were equally placed around the surface of the forearm for the voltage measurements. The model was solved using Finite Element Method (FEM) and dynamic image was reconstructed using truncated singular value decomposition (TSVD) regularization method. The conductivity distributions were compared with different current injections, along the meridian channel and channels around respectively. We also conducted experiments on models and the meridians were shown in final reconstructed images.

  20. Parametric electrical impedance tomography for measuring bone mineral density in the pelvis using a computational model.

    PubMed

    Kimel-Naor, Shani; Abboud, Shimon; Arad, Marina

    2016-08-01

    Osteoporosis is defined as bone microstructure deterioration resulting a decrease of bone's strength. Measured bone mineral density (BMD) constitutes the main tool for Osteoporosis diagnosis, management, and defines patient's fracture risk. In the present study, parametric electrical impedance tomography (pEIT) method was examined for monitoring BMD, using a computerized simulation model and preliminary real measurements. A numerical solver was developed to simulate surface potentials measured over a 3D computerized pelvis model. Varying cortical and cancellous BMD were simulated by changing bone conductivity and permittivity. Up to 35% and 16% change was found in the real and imaginary modules of the calculated potential, respectively, while BMD changes from 100% (normal) to 60% (Osteoporosis). Negligible BMD relative error was obtained with SNR>60 [dB]. Position changes errors indicate that for long term monitoring, measurement should be taken at the same geometrical configuration with great accuracy. The numerical simulations were compared to actual measurements that were acquired from a healthy male subject using a five electrodes belt bioimpedance device. The results suggest that pEIT may provide an inexpensive easy to use tool for frequent monitoring BMD in small clinics during pharmacological treatment, as a complementary method to DEXA test. PMID:27185035

  1. Three-dimensional electrical impedance tomography applied to a metal-walled filtration test platform

    NASA Astrophysics Data System (ADS)

    Davidson, J. L.; Ruffino, L. S.; Stephenson, D. R.; Mann, R.; Grieve, B. D.; York, T. A.

    2004-11-01

    The first true three-dimensional image reconstructions from a metal-walled vessel using electrical impedance tomography (EIT) are presented. Two image reconstruction techniques have been applied via relatively sophisticated FEM modelling of a bespoke laboratory test vessel from which data have been obtained using an EIT instrument designed to intrinsically safe requirements. A generalized Tikhonov regularization method is compared with the linear back-projection (LBP) technique. Subsequent image reconstructions strongly suggest that the LBP method when applied to a metal-walled vessel is highly sensitive to the level of detail within the FEM model. By comparison, the regularized technique is far less sensitive to the complexity of the modelled geometry. Additionally, unlike the LBP method, the regularization technique has been successful in accurately reconstructing multiple inhomogeneities within an aqueous system. A further experiment has shown similar sensitivity in a wetted powder-based system. It is concluded that EIT via a regularized difference imaging approach has significant potential for detecting 3D malformations and non-uniformities in industrial pressure filtration systems.

  2. A fast parallel solver for the forward problem in electrical impedance tomography.

    PubMed

    Jehl, Markus; Dedner, Andreas; Betcke, Timo; Aristovich, Kirill; Klöfkorn, Robert; Holder, David

    2015-01-01

    Electrical impedance tomography (EIT) is a noninvasive imaging modality, where imperceptible currents are applied to the skin and the resulting surface voltages are measured. It has the potential to distinguish between ischaemic and haemorrhagic stroke with a portable and inexpensive device. The image reconstruction relies on an accurate forward model of the experimental setup. Because of the relatively small signal in stroke EIT, the finite-element modeling requires meshes of more than 10 million elements. To study the requirements in the forward modeling in EIT and also to reduce the time for experimental image acquisition, it is necessary to reduce the run time of the forward computation. We show the implementation of a parallel forward solver for EIT using the Dune-Fem C++ library and demonstrate its performance on many CPU's of a computer cluster. For a typical EIT application a direct solver was significantly slower and not an alternative to iterative solvers with multigrid preconditioning. With this new solver, we can compute the forward solutions and the Jacobian matrix of a typical EIT application with 30 electrodes on a 15-million element mesh in less than 15 min. This makes it a valuable tool for simulation studies and EIT applications with high precision requirements. It is freely available for download. PMID:25069109

  3. Probing the biocompatibility of MoS2 nanosheets by cytotoxicity assay and electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Shah, Pratikkumar; Narayanan, Tharangattu N.; Li, Chen-Zhong; Alwarappan, Subbiah

    2015-08-01

    Transition metal dichalgogenides such as MoS2 have recently emerged as hot two-dimensional (2D) materials due to their superior electronic and catalytic properties. Recently, we have reported the usefulness of MoS2 nanosheets toward the electrochemical detection of neurotransmitters and glucose (Narayanan et al 2014 Nanotechnology 25 335702). Furthermore, there are reports available in the literature that demonstrate the usefulness of MoS2 nanosheets for biosensing and energy storage applications (Zhu et al 2013 J. Am. Chem. Soc. 135 5998-6001 Pumera and Loo 2014 Trends Anal. Chem. 61 49-53 Lee et al 2014 Sci. Rep. 4 7352; Stephenson et al 2014 Energy Environ. Sci. 7 209-31). Understanding the cytotoxic effect of any material is very important prior to employing them for any in vivo biological applications such as implantable sensors, chips, or carriers for drug delivery and cell imaging purposes. Herein, we report the cytotoxicity of the MoS2 nanosheets based on the cytotoxic assay results and electrical impedance analysis using rat pheochromocytoma cells (PC12) and rat adrenal medulla endothelial cells (RAMEC). Our results indicated that the MoS2 nanosheets synthesized in our work are safe 2D nanosheets for futuristic biomedical applications.

  4. A comparison framework for temporal image reconstructions in electrical impedance tomography.

    PubMed

    Gagnon, Hervé; Grychtol, Bartłomiej; Adler, Andy

    2015-06-01

    Electrical impedance tomography (EIT) provides low-resolution images of internal conductivity distributions, but is able to achieve relatively high temporal resolutions. Most EIT image reconstruction algorithms do not explicitly account for the temporal constraints on the measurements or physiological processes under investigation. Instead, algorithms typically assume both that the conductivity distribution does not change during the acquisition of each EIT data frame, and that frames can be reconstructed independently, without consideration of the correlation between images. A failure to account for these temporal effects will result in aliasing-related artefacts in images. Several methods have been proposed to compensate for these effects, including interpolation of raw data, and reconstruction algorithms using Kalman and temporal filtering. However, no systematic work has been performed to understand the severity of the temporal artefacts nor the extent to which algorithms can account for them. We seek to address this need by developing a temporal comparison framework and figures of merit to assess the ability of reconstruction algorithms to account for temporal effects. Using this approach, we compare combinations of three reconstruction algorithms using three EIT data frame types: perfect, realistic and interpolated. The results show that, without accounting for temporal effects, artefacts are present in images for dynamic conductivity contrasts at frequencies 10-20 times slower than the frame rate. The proposed methods show some improvements in reducing these artefacts. PMID:26006181

  5. The Effect of Subcutaneous Fat on Electrical Impedance Myography: Electrode Configuration and Multi-Frequency Analyses.

    PubMed

    Li, Le; Li, Xiaoyan; Hu, Huijing; Shin, Henry; Zhou, Ping

    2016-01-01

    This study investigates the impact of the subcutaneous fat layer (SFL) thickness on localized electrical impedance myography (EIM), as well as the effects of different current electrodes, varying in distance and direction, on EIM output. Twenty-three healthy subjects underwent localized multi-frequency EIM on their biceps brachii muscles with a hand-held electrode array. The EIM measurements were recorded under three different configurations: wide (or outer) longitudinal configuration 6.8 cm, narrow (or inner) longitudinal configuration 4.5 cm, and narrow transverse configuration 4.5 cm. Ultrasound was applied to measure the SFL thickness. Coefficients of determination (R2) of three EIM variables (resistance, reactance, and phase) and SFL thickness were calculated. For the longitudinal configuration, the wide distance could reduce the effects of the subcutaneous fat when compared with the narrow distance, but a significant correlation still remained for all three EIM parameters. However, there was no significant correlation between SFL thickness and reactance in the transverse configuration (R2 = 0.0294, p = 0.434). Utilizing a ratio of 50kHz/100kHz phase was found to be able to help reduce the correlation with SFL thickness for all the three configurations. The findings indicate that the appropriate selection of the current electrode distance, direction and the multi-frequency phase ratio can reduce the impact of subcutaneous fat on EIM. These settings should be evaluated for future clinical studies using hand-held localized arrays to perform EIM. PMID:27227876

  6. In vitro localisation of intracranial haematoma using electrical impedance tomography semi-array.

    PubMed

    Ayati, S Bentolhoda; Bouazza-Marouf, Kaddour; Kerr, David

    2015-01-01

    Electrical Impedance Tomography is a non-invasive and portable method that has good potential as an alternative to the conventional modalities for early detection of intracranial haematomas in high risk patients. Early diagnosis can reduce treatment delays and most significantly can impact patient outcomes. Two eight-electrode layouts, a standard ring full array (FA) and a semi-array (SA), were investigated for their ability to detect, localise and quantify simulated intracranial haematomas in vitro on ovine models for the purpose of early diagnosis. SA layout speeds up electrode application and avoids the need to move and lift the patient's head. Haematomas were simulated using gel samples with the same conductivity as blood. Both layouts, FA and SA, could detect the presence of haematomas at any location within the skull. The mean of the relative radial position error with respect to the brain radius was 7% for FA and 6% for SA, for haematomas close to the electrodes, and 11% for SA for haematomas far from the electrodes at the back of the head. Size estimation was not as good; the worst size estimation error for FA being around 30% while the best for SA was 50% for simulated haematomas close to the electrodes. PMID:25455163

  7. Process techniques for human thoracic electrical bio-impedance signal in remote healthcare systems.

    PubMed

    Rahman, Muhammad Zia Ur; Mirza, Shafi Shahsavar

    2016-06-01

    Analysis of thoracic electrical bio-impedance (TEB) facilitates heart stroke volume in sudden cardiac arrest. This Letter proposes several efficient and computationally simplified adaptive algorithms to display high-resolution TEB component. In a clinical environment, TEB signal encounters with various physiological and non-physiological phenomenon, which masks the tiny features that are important in identifying the intensity of the stroke. Moreover, computational complexity is an important parameter in a modern wearable healthcare monitoring tool. Hence, in this Letter, the authors propose a new signal conditioning technique for TEB enhancement in remote healthcare systems. For this, the authors have chosen higher order adaptive filter as a basic element in the process of TEB. To improve filtering capability, convergence speed, to reduce computational complexity of the signal conditioning technique, the authors apply data normalisation and clipping the data regressor. The proposed implementations are tested on real TEB signals. Finally, simulation results confirm that proposed regressor clipped normalised higher order filter is suitable for a practical healthcare system. PMID:27382481

  8. A Novel Method for Monitoring Data Quality in Electrical Impedance Tomography

    NASA Astrophysics Data System (ADS)

    Adler, Andy; Grychtol, Bartłomiej; Gaggero, Pascal; Justiz, Jörn; Koch, Volker; Mamatjan, Yasin

    2013-04-01

    Electrical impedance tomography (EIT) has the promise to help improve care for patients undergoing ventilation therapy by providing real-time bed-side information on the distribution of ventilation in their lungs. To realise this potential, it is important for an EIT system to provide a reliable and meaningful signal at all times, or alert clinicians when this is not possible. Because the reconstructed images in EIT are sensitive to system instabilities (including electrode connection problems) and artifacts caused by e.g. movement or sweat, there is a need for EIT systems to continuously monitor, recognize and, if possible, correct for such errors. Motivated by this requirement, our paper describes a novel approach to quantitatively measure EIT data quality suitable for online and offline applications. We used a publicly available data set of ventilation data from two pediatric patients with lung disease to evaluate the data quality on clinical data. Results suggest that the developed data quality could be a useful tool for real-time assessment of the quality of EIT data and, hence, to indicate the reliability of any derived physiological information.

  9. Induced current electrical impedance tomography system: experimental results and numerical simulations.

    PubMed

    Zlochiver, Sharon; Radai, M Michal; Abboud, Shimon; Rosenfeld, Moshe; Dong, Xiu-Zhen; Liu, Rui-Gang; You, Fu-Sheng; Xiang, Hai-Yan; Shi, Xue-Tao

    2004-02-01

    In electrical impedance tomography (EIT), measurements of developed surface potentials due to applied currents are used for the reconstruction of the conductivity distribution. Practical implementation of EIT systems is known to be problematic due to the high sensitivity to noise of such systems, leading to a poor imaging quality. In the present study, the performance of an induced current EIT (ICEIT) system, where eddy current is applied using magnetic induction, was studied by comparing the voltage measurements to simulated data, and examining the imaging quality with respect to simulated reconstructions for several phantom configurations. A 3-coil, 32-electrode ICEIT system was built, and an iterative modified Newton-Raphson algorithm was developed for the solution of the inverse problem. The RMS norm between the simulated and the experimental voltages was found to be 0.08 +/- 0.05 mV (<3%). Two regularization methods were implemented and compared: the Marquardt regularization and the Laplacian regularization (a bounded second-derivative regularization). While the Laplacian regularization method was found to be preferred for simulated data, it resulted in distinctive spatial artifacts for measured data. The experimental reconstructed images were found to be indicative of the angular positioning of the conductivity perturbations, though the radial sensitivity was low, especially when using the Marquardt regularization method. PMID:15005319

  10. Electrical Impedance Tomography for pulmonary oedema extent monitoring: review and updated design

    NASA Astrophysics Data System (ADS)

    Santos, Eduardo; Simini, Franco

    2012-12-01

    Monitoring pulmonary oedema would be greatly facilitated by the availability of a graphical representation of its size and density to guide therapeutic interventions. Currently the clinician has only indirect estimations because X-ray imaging or computed tomography can not be repeated often. To avoid the transfer of critically ill patients and to have continuous information Electrical Impedance Tomography (EIT) is suggested. Circuit designs for EIT are reviewed, including wave generators, current sources, differential amplifiers, synchronous voltmeters, multiplexers and control modules. Nine designs are studied, the characteristics of five of them are presented (UK 2005, Uruguay 2002, Iran 2006, China 2007 and Switzerland 2012). Three different solutions are compared (components cost range from) and an optimal design is proposed which includes a direct digital synthesizer (DDS) for signal generation, a modified Howland configuration for current source, 16 bits for the analog to digital conversion, and a digital signal processor (DSP) for the synchronous demodulation as well as to process the measurements for the reconstruction algorithm. This allows us to design low cost, gross graphical representations for oedema extent monitoring, with little anatomical accuracy.

  11. The Effect of Subcutaneous Fat on Electrical Impedance Myography: Electrode Configuration and Multi-Frequency Analyses

    PubMed Central

    Li, Le; Li, Xiaoyan; Hu, Huijing; Shin, Henry

    2016-01-01

    This study investigates the impact of the subcutaneous fat layer (SFL) thickness on localized electrical impedance myography (EIM), as well as the effects of different current electrodes, varying in distance and direction, on EIM output. Twenty-three healthy subjects underwent localized multi-frequency EIM on their biceps brachii muscles with a hand-held electrode array. The EIM measurements were recorded under three different configurations: wide (or outer) longitudinal configuration 6.8 cm, narrow (or inner) longitudinal configuration 4.5 cm, and narrow transverse configuration 4.5 cm. Ultrasound was applied to measure the SFL thickness. Coefficients of determination (R2) of three EIM variables (resistance, reactance, and phase) and SFL thickness were calculated. For the longitudinal configuration, the wide distance could reduce the effects of the subcutaneous fat when compared with the narrow distance, but a significant correlation still remained for all three EIM parameters. However, there was no significant correlation between SFL thickness and reactance in the transverse configuration (R2 = 0.0294, p = 0.434). Utilizing a ratio of 50kHz/100kHz phase was found to be able to help reduce the correlation with SFL thickness for all the three configurations. The findings indicate that the appropriate selection of the current electrode distance, direction and the multi-frequency phase ratio can reduce the impact of subcutaneous fat on EIM. These settings should be evaluated for future clinical studies using hand-held localized arrays to perform EIM. PMID:27227876

  12. Assessment of distribution of ventilation by electrical impedance tomography in standing horses.

    PubMed

    Ambrisko, T D; Schramel, J P; Adler, A; Kutasi, O; Makra, Z; Moens, Y P S

    2016-02-01

    The aim was to evaluate the feasibility of using electrical impedance tomography (EIT) in horses. Thoracic EIT was used in nine horses. Thoracic and abdominal circumference changes were also measured with respiratory ultrasound plethysmography (RUP). Data were recorded during baseline, rebreathing of CO2 and sedation. Three breaths were selected for analysis from each recording. During baseline breathing, horses regularly took single large breaths (sighs), which were also analysed. Functional EIT images were created using standard deviations (SD) of pixel signals and correlation coefficients (R) of each pixel signal with a reference respiratory signal. Left-to-right ratio, centre-of-ventilation and global-inhomogeneity-index were calculated. RM-ANOVA and Bonferroni tests were used (P < 0.05). Distribution of ventilation shifted towards right during sighs and towards dependent regions during sighs, rebreathing and sedation. Global-inhomogeneity-index did not change for SD but increased for R images during sedation. The sum of SDs for the respiratory EIT signals correlated well with thoracic (r(2) = 0.78) and abdominal (r(2) = 0.82) tidal circumferential changes. Inverse respiratory signals were identified on the images at sternal location and based on reviewing CT images, seemed to correspond to location of gas filled intestines. Application of EIT in standing non-sedated horses is feasible. EIT images may provide physiologically useful information even in situations, such as sighs, that cannot easily be tested by other methods. PMID:26711858

  13. On the influence of spread constant in radial basis networks for electrical impedance tomography.

    PubMed

    Martin, Sébastien; Choi, Charles T M

    2016-06-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technique. The main task of this work is to solve a non-linear inverse problem, for which several techniques have been suggested, but none of which gives a very high degree of accuracy. This paper introduces a novel approach, based on radial basis function (RBF) artificial neural networks (ANNs), to solve this problem, and uses several ANNs to obtain the best solution to the EIT inverse problem. ANNs have the potential to directly estimate the solution of the inverse problem with a high degree of accuracy. While different radial basis neural networks do not always perform well on different problems, they usually give good results on some specific problems. This paper evidences a strong correlation between the area of the target and the spread constant of the RBF network that gives the best reconstruction. A solution to automatically estimate the size of the target and pick the best neural network directly from voltage measurements is presented, making the reconstruction process automatic. By automatically selecting the best ANN for each specific set of voltage measurements, the proposed solution gives a more accurate reconstruction of both small and large targets. PMID:27203367

  14. Electrical impedance myography for the assessment of children with muscular dystrophy: a preliminary study

    NASA Astrophysics Data System (ADS)

    Rutkove, S. B.; Darras, B. T.

    2013-04-01

    Electrical impedance myography (EIM) provides a non-invasive approach for quantifying the severity of neuromuscular disease. Here we determine how well EIM data correlates to functional and ultrasound (US) measures of disease in children with Duchenne muscular dystrophy (DMD) and healthy subjects. Thirteen healthy boys, aged 2-12 years and 14 boys with DMD aged 4-12 years underwent both EIM and US measurements of deltoid, biceps, wrist flexors, quadriceps, tibialis anterior, and medial gastrocnemius. EIM measurements were performed with a custom-designed probe using a commercial multifrequency bioimpedance device. US luminosity data were quantified using a gray-scale analysis approach. Children also underwent the 6-minute walk test, timed tests and strength measurements. EIM and US data were combined across muscles. EIM 50 kHz phase was able to discriminate DMD children from healthy subjects with 98% accuracy. In the DMD patients, average EIM phase measurements also correlated well with standard functional measures. For example the 50 kHz phase correlated with the Northstar Ambulatory Assessment test (R = 0.83, p = 0.02). EIM 50 kHz phase and US correlated as well, with R = -0.79 (p < 0.001). These results show that EIM provides valuable objective measures Duchenne muscular dystrophy severity.

  15. In vivo imaging of irreversible electroporation by means of electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Granot, Yair; Ivorra, Antoni; Maor, Elad; Rubinsky, Boris

    2009-08-01

    Electroporation, the increased permeability of cell membranes due to a large transmembrane voltage, is an important clinical tool. Both reversible and irreversible in vivo electroporation are used for clinical applications such as gene therapy and solid malignant tumor ablation, respectively. The primary advantage of in vivo electroporation is the ability to treat tissue in a local and minimally invasive fashion. The drawback is the current lack of control over the process. This paper is the first report of a new method for real-time three-dimensional imaging of an in vivo electroporation process. Using two needle electrodes for irreversible electroporation and a set of electrodes for reconstructing electrical impedance tomography (EIT) images of the treated tissue, we were able to demonstrate electroporation imaging in rodent livers. Histology analysis shows good correlation between the extent of tissue damage caused by irreversible electroporation and the EIT images. This new method may lead the way to real-time control over genetic treatment of diseases in tissue and tissue ablation.

  16. The potential of electrical impedance on the performance of galloping systems for energy harvesting and control applications

    NASA Astrophysics Data System (ADS)

    Abdelmoula, H.; Abdelkefi, A.

    2016-05-01

    Performances of galloping-based piezoelectric systems for energy harvesting and control applications when considering complex electrical impedance are investigated. The aeroelastic system is composed of a unimorph piezoelectric cantilever beam with a square cylinder attached at its tip and subjected to a uniform flow speed. A quasi-steady representation is used to model the aerodynamic force. A nonlinear distributed-parameter model is developed when considering various scenarios of connections between electrical resistance, capacitance, and inductance. Theoretical strategies are developed in order to determine the relation between the onset speed of galloping and the components of the electrical impedance. The results show that the presence of the electrical capacitance and inductance is not beneficial in terms of improving the levels of the harvested power crossing the load resistance. On the other hand, it is shown that the inclusion of these electrical components may be useful for energy harvesting purposes when charging/discharging batteries. One of the important findings of this research study is that including an electrical inductance in connection to a load resistance is very beneficial for control purposes because a significant increase in the onset speed of instability can be obtained for well-defined values of the electrical components. Analytical predictions of these optimum values of the electrical inductance and resistance are determined and compared with numerical simulations. It is also demonstrated that supercritical Hopf bifurcations take place at this controlled optimal configuration without having any hysteresis and jumps when increasing and decreasing the wind speeds.

  17. Respiratory-gated electrical impedance tomography: a potential technique for quantifying stroke volume

    NASA Astrophysics Data System (ADS)

    Arshad, Saaid H.; Murphy, Ethan K.; Halter, Ryan J.

    2016-03-01

    Telemonitoring is becoming increasingly important as the proportion of the population living with cardiovascular disease (CVD) increases. Currently used health parameters in the suite of telemonitoring tools lack the sensitivity and specificity to accurately predict heart failure events, forcing physicians to play a reactive versus proactive role in patient care. A novel cardiac output (CO) monitoring device is proposed that leverages a custom smart phone application and a wearable electrical impedance tomography (EIT) system. The purpose of this work is to explore the potential of using respiratory-gated EIT to quantify stroke volume (SV) and assess its feasibility using real data. Simulations were carried out using the 4D XCAT model to create anatomically realistic meshes and electrical conductivity profiles representing the human thorax and the intrathoracic tissue. A single 5-second period respiration cycle with chest/lung expansion was modeled with end-diastole (ED) and end-systole (ES) heart volumes to evaluate how effective EIT-based conductivity changes represent clinically significant differences in SV. After establishing a correlation between conductivity changes and SV, the applicability of the respiratory-gated EIT was refined using data from the PhysioNet database to estimate the number of useful end-diastole (ED) and end-systole (ES) heart events attained over a 3.3 minute period. The area associated with conductivity changes was found to correlate to SV with a correlation coefficient of 0.92. A window of 12.5% around peak exhalation was found to be the optimal phase of the respiratory cycle from which to record EIT data. Within this window, ~47 useable ED and ES were found with a standard deviation of 28 using 3.3 minutes of data for 20 patients.

  18. Novel microfluidic system for online monitoring of biofilm dynamics by electrical impedance spectroscopy and amperometry

    NASA Astrophysics Data System (ADS)

    Bruchmann, Julia; Sachsenheimer, Kai; Schwartz, Thomas; Rapp, Bastian E.

    2016-03-01

    Biofilm formation is ubiquitous in nature where microorganisms attach to surfaces and form highly adapted and protected communities. In technical and industrial systems like drinking water supply, food production or shipping industry biofilms are a major cause of product contamination, biofouling, and biocorrosion. Therefore, understanding of biofilm formation and means of preventing biofilm formation is important to develop novel biofilm treatment strategies. A system allowing directly online detection and monitoring biofilm formation is necessary. However, until today, there are little to none technical systems featuring a non-destructive real-time characterization of biofilm formation in a highthroughput manner. This paper presents such a microfluidic system based on electrical impedance spectroscopy (EIS) and amperomertic current measurement. The sensor consists of four modules, each housing 24 independent electrodes within 12 microfluidic channels. Attached biomass on the electrodes is monitored as increased inhibition in charge transfer by EIS and a change in metabolic activity is measured as change in produced electric current by amperometry. This modular sensor system is highly adaptable and suitable for a broad range of microbiological applications. Among others, biofilm formation processes can be characterized online, biofilm manipulation like inactivation or destabilization can be monitored in real-time and gene expression can be analyzed in parallel. The use of different electrode designs allows effective biofilm studies during all biofilm phases. The whole system was recently extended by an integrated pneumatic microfluidic pump which enables easy handling procedures. Further developments of this pumping module will allow a fully- automated computer-controlled valving and pumping.

  19. FPGA-based voltage and current dual drive system for high frame rate electrical impedance tomography.

    PubMed

    Khan, Shadab; Manwaring, Preston; Borsic, Andrea; Halter, Ryan

    2015-04-01

    Electrical impedance tomography (EIT) is used to image the electrical property distribution of a tissue under test. An EIT system comprises complex hardware and software modules, which are typically designed for a specific application. Upgrading these modules is a time-consuming process, and requires rigorous testing to ensure proper functioning of new modules with the existing ones. To this end, we developed a modular and reconfigurable data acquisition (DAQ) system using National Instruments' (NI) hardware and software modules, which offer inherent compatibility over generations of hardware and software revisions. The system can be configured to use up to 32-channels. This EIT system can be used to interchangeably apply current or voltage signal, and measure the tissue response in a semi-parallel fashion. A novel signal averaging algorithm, and 512-point fast Fourier transform (FFT) computation block was implemented on the FPGA. FFT output bins were classified as signal or noise. Signal bins constitute a tissue's response to a pure or mixed tone signal. Signal bins' data can be used for traditional applications, as well as synchronous frequency-difference imaging. Noise bins were used to compute noise power on the FPGA. Noise power represents a metric of signal quality, and can be used to ensure proper tissue-electrode contact. Allocation of these computationally expensive tasks to the FPGA reduced the required bandwidth between PC, and the FPGA for high frame rate EIT. In 16-channel configuration, with a signal-averaging factor of 8, the DAQ frame rate at 100 kHz exceeded 110 frames s (-1), and signal-to-noise ratio exceeded 90 dB across the spectrum. Reciprocity error was found to be for frequencies up to 1 MHz. Static imaging experiments were performed on a high-conductivity inclusion placed in a saline filled tank; the inclusion was clearly localized in the reconstructions obtained for both absolute current and voltage mode data. PMID:25376037

  20. Electrical impedance tomography in 3D using two electrode planes: characterization and evaluation.

    PubMed

    Wagenaar, Justin; Adler, Andy

    2016-06-01

    Electrical impedance tomography (EIT) uses body surface electrical stimulation and measurements to create conductivity images; it shows promise as a non-invasive technology to monitor the distribution of lung ventilation. Most applications of EIT have placed electrodes in a 2D ring around the thorax, and thus produced 2D cross-sectional images. These images are unable to distinguish out-of-plane contributions, or to image volumetric effects. Volumetric EIT can be calculated using multiple electrode planes and a 3D reconstruction algorithm. However, while 3D reconstruction algorithms are available, little has been done to understand the performance of 3D EIT in terms of the measurement configurations available. The goal of this paper is to characterize the phantom and in vivo performance of 3D EIT with two electrode planes. First, phantom measurements are used to measure the reconstruction characteristics of seven stimulation and measurement configurations. Measurements were then performed on eight healthy volunteers as a function of body posture, postures, and with various electrode configurations. Phantom results indicate that 3D EIT using two rings of electrodes provides reasonable resolution in the electrode plane but low vertical resolution. For volunteers, functional EIT images are created from inhalation curve features to analyze the effect of posture (standing, sitting, supine and decline) on regional lung behaviour. An ability to detect vertical changes in lung volume distribution was shown for two electrode configurations. Based on tank and volunteer results, we recommend the use of the 'square' stimulation and measurement pattern for two electrode plane EIT. PMID:27203154

  1. Regional lung response to bronchodilator reversibility testing determined by electrical impedance tomography in chronic obstructive pulmonary disease.

    PubMed

    Vogt, Barbara; Zhao, Zhanqi; Zabel, Peter; Weiler, Norbert; Frerichs, Inéz

    2016-07-01

    Patients with obstructive lung diseases commonly undergo bronchodilator reversibility testing during examination of their pulmonary function by spirometry. A positive response is defined by an increase in forced expiratory volume in 1 s (FEV1). FEV1 is a rather nonspecific criterion not allowing the regional effects of bronchodilator to be assessed. We employed the imaging technique of electrical impedance tomography (EIT) to visualize the spatial and temporal ventilation distribution in 35 patients with chronic obstructive pulmonary disease at baseline and 5, 10, and 20 min after bronchodilator inhalation. EIT scanning was performed during tidal breathing and forced full expiration maneuver in parallel with spirometry. Ventilation distribution was determined by EIT by calculating the image pixel values of FEV1, forced vital capacity (FVC), tidal volume, peak flow, and mean forced expiratory flow between 25 and 75% of FVC. The global inhomogeneity indexes of each measure and histograms of pixel FEV1/FVC values were then determined to assess the bronchodilator effect on spatial ventilation distribution. Temporal ventilation distribution was analyzed from pixel values of times needed to exhale 75 and 90% of pixel FVC. Based on spirometric FEV1, significant bronchodilator response was found in 17 patients. These patients exhibited higher postbronchodilator values of all regional EIT-derived lung function measures in contrast to nonresponders. Ventilation distribution was inhomogeneous in both groups. Significant improvements were noted for spatial distribution of pixel FEV1 and tidal volume and temporal distribution in responders. By providing regional data, EIT might increase the diagnostic and prognostic information derived from reversibility testing. PMID:27190067

  2. Lumped Element Electrical Model based on Three Resistors for Electrical Impedance in Radiofrequency Cardiac Ablation: Estimations from Analytical Calculations and Clinical Data

    PubMed Central

    Berjano, Enrique; d'Avila, Andre

    2013-01-01

    The electrical impedance measured during radiofrequency cardiac ablation (RFCA) is widely used in clinical studies to predict the heating evolution and hence the success of the procedure. We hypothesized that a model based on three resistors in series can mimic the total electrical impedance measured during RFCA. The three resistors or impedances are given by: impedance associated with the tissue around the active electrode (myocardium and circulating blood) (Z-A), that associated with the tissue around the dispersive electrode (Z-DE) and that associated with the rest of the body (Z-B). Our objective was to quantify the values associated with these three impedance types by an analytical method, after which the values obtained would be compared to those estimated from clinical data from previous studies. The results suggest that an RFCA using a 7 Fr 4-mm electrode would give a Z-A of around 75 ohms, a Z-DE around 20 ohms, and Z-B would be 15±10 ohms (for body surface area variations between 1.5 and 2.5 m^2). Finally, adaptations of the proposed model were used to explain the results of previous clinical studies using a different electrode arrangement, such as in bipolar ablation of the ventricular septum. PMID:23961299

  3. Modeling of the dye loading time influence on the electrical impedance of a dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Pugliese, D.; Shahzad, N.; Sacco, A.; Tresso, E.; Alexe-Ionescu, A. L.

    2013-09-01

    A hemisquaraine dye molecule (CT1) was used as TiO2 sensitizer. The influence of the dye-adsorption time on the electrical impedance of a CT1-based dye-sensitized solar cell (DSC) was analyzed. Differently from what we observed with commercial Ru dye-based DSC, a non-monotonic effect of the impregnation time on the impedance has been found and the dye loading time is much reduced, a desirable outcome in economic grounds. This feature is analyzed in terms of the dye molecules tendency to aggregate close to the TiO2/electrolyte interface. A physical model that fits well the experimental data is proposed, which also takes into account a correction related to the difference between the illuminated area of the cell and the total area available in the electrical measurements.

  4. Experimental impedance investigation of an ultracapacitor at different conditions for electric vehicle applications

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Hu, Xiaosong; Wang, Zhenpo; Sun, Fengchun; Dorrell, David G.

    2015-08-01

    Ultracapacitors (UCs) are being increasingly deployed as a short-term energy storage device in various energy systems including uninterruptable power supplies, electrified vehicles, renewable energy systems, and wireless communication. They exhibit excellent power density and energy efficiency. The dynamic behavior of a UC, however, strongly depends on its impedance characteristics. In this paper, the impedance characteristics of a commercial UC are experimentally investigated through the well-adopted Electrochemical Impedance Spectroscopy (EIS) technique. The implications of the UC operating conditions (i.e., temperature and state of charge (SOC)) to the impedance are systematically examined. The results show that the impedance is highly sensitive to the temperature and SOC; and the temperature effect is more significant. In particular, the coupling effect between the temperature and SOC is illustrated, as well as the high-efficiency SOC window, which is highlighted. To further verify the reliability of the EIS-based investigation and to probe the sensitivity of UC parameters to the operating conditions, a dynamic model is characterized by fitting the collected impedance data. The interdependence of UC parameters (i.e., capacitance and resistance elements) on the temperature and SOC is quantitatively revealed. The impedance-based model is demonstrated to be accurate in two driving-cycle tests.

  5. Single cell studies of mouse embryonic stem cell (mESC) differentiation by electrical impedance measurements in a microfluidic device.

    PubMed

    Zhou, Ying; Basu, Srinjan; Laue, Ernest; Seshia, Ashwin A

    2016-07-15

    Biological populations of cells show considerable cell-to-cell variability. Study of single cells and analysis of cell heterogeneity are considered to be critical in understanding biological processes such as stem cell differentiation and cancer development. Recent advances in lab-on-a-chip techniques have allowed single-cell capture in microfluidic channels with the possibility of precise environmental control and high throughput of experiments with minimal usage of samples and reagents. In recent years, label-free techniques such as electrical impedance spectroscopy have emerged as a non-invasive approach to studying cell properties. In this study, we have designed and fabricated a microfluidic device that combines hydrodynamic trapping of single cells in pre-defined locations with the capability of running electrical impedance measurements within the same device. We have measured mouse embryonic stem cells (mESCs) at different states during differentiation (t=0h, 24h and 48h) and quantitatively analysed the changes in electrical parameters of cells during differentiation. A marked increase in the magnitude of the cell impedance is found during cell differentiation, which can be attributed to an increase in cell size. The analysis of the measurements shows that the nucleus-to-cytoplasm ratio decreases during this process. The degree of cell heterogeneity is observed to be the highest when the cells are at the transition state (24h), compare with cells at undifferentiated (0h) and fully differentiated (48h) states. The device enables highly efficient single cell trapping and provides sensitive, label-free electrical impedance measurements of individual cells, enabling the possibility of quantitatively analysing their physical state as well as studying the associated heterogeneity of a cell population. PMID:26963790

  6. Single cell studies of mouse embryonic stem cell (mESC) differentiation by electrical impedance measurements in a microfluidic device

    PubMed Central

    Zhou, Ying; Basu, Srinjan; Laue, Ernest; Seshia, Ashwin A.

    2016-01-01

    Biological populations of cells show considerable cell-to-cell variability. Study of single cells and analysis of cell heterogeneity are considered to be critical in understanding biological processes such as stem cell differentiation and cancer development. Recent advances in lab-on-a-chip techniques have allowed single-cell capture in microfluidic channels with the possibility of precise environmental control and high throughput of experiments with minimal usage of samples and reagents. In recent years, label-free techniques such as electrical impedance spectroscopy have emerged as a non-invasive approach to studying cell properties. In this study, we have designed and fabricated a microfluidic device that combines hydrodynamic trapping of single cells in pre-defined locations with the capability of running electrical impedance measurements within the same device. We have measured mouse embryonic stem cells (mESCs) at different states during differentiation (t=0 h, 24 h and 48 h) and quantitatively analysed the changes in electrical parameters of cells during differentiation. A marked increase in the magnitude of the cell impedance is found during cell differentiation, which can be attributed to an increase in cell size. The analysis of the measurements shows that the nucleus-to-cytoplasm ratio decreases during this process. The degree of cell heterogeneity is observed to be the highest when the cells are at the transition state (24 h), compare with cells at undifferentiated (0 h) and fully differentiated (48 h) states. The device enables highly efficient single cell trapping and provides sensitive, label-free electrical impedance measurements of individual cells, enabling the possibility of quantitatively analysing their physical state as well as studying the associated heterogeneity of a cell population. PMID:26963790

  7. An electrically scanned thinned array radiometer for Earth remote sensing

    NASA Technical Reports Server (NTRS)

    Griffis, Andrew J.; Swift, Calvin T.; Levine, David

    1991-01-01

    Interferometric aperture synthesis is being investigated as an alternative to real aperture measurements of the brightness temperature of the earth from low earth orbit. Aperture synthesis allows for the realization of space borne microwave systems with attractive spatial resolution characteristics. Radio astronomers have performed aperture synthesis by cross-correlating spatially separated antenna element pairs for some time. The application of this technique to the observation of a distributed source, as opposed to a point source in radio astronomy, presents a novel and challenging application of aperture synthesis. The demonstration of this geophysical application of aperture synthesis was carried out by constructing and flight testing a phototype instrument, the Electrically Scanned Thinned Array Radiometer (ESTAR). The subsequent data analysis and image reconstruction yielded an image of the eastern shore of Virginia. In the past year, more data of the same region were taken and analyzed, as well as for other regions of Virginia, Pennsylvania, and Maine. Improvements were made in the image reconstruction technique and in the system electronics for the current and upcoming instruments (ESTAR00 and ESTAR0, respectively), particularly in terms of calibration instrumentation and techniques.

  8. Dynamic separation of pulmonary and cardiac changes in electrical impedance tomography.

    PubMed

    Deibele, J M; Luepschen, H; Leonhardt, S

    2008-06-01

    In spontaneously breathing or ventilated subjects, it is difficult to image cardiac-related conductivity changes using electrical impedance tomography (EIT) due to the high amplitude of the ventilation component. Previous attempts to separate these components included either electrocardiogram-gated averaging, frequency domain filtering or holding the breath while performing the measurements. However, such methods are either not able to produce continuous real-time images or to fully separate cardiac and pulmonary changes. The aim of this work was to develop a new dynamic filtering method for the online separation of pulmonary and cardiac changes avoiding the drawbacks of the previous attempts. The approach is based on estimating template functions for the pulmonary and cardiac components by means of principal component analysis and frequency domain filtering. Then, these templates are fitted into the input signals. The new method enables an observer to examine the variation of the cardiac signal beat-by-beat after a one-time setup period of 20 s. Preliminary in vivo results of two healthy subjects are presented. The results are superior to frequency domain filtering and in good agreement with signals averaged over several cardiac cycles. The method does not depend on ECG or other a priori knowledge. The apparent validity of the method's ability to separate cardiac and pulmonary changes in EIT images was shown and has to be confirmed in future studies. The algorithm opens up new possibilities for future clinical trials on continuous monitoring by means of EIT and for the examination of the relation between the cardiac component and lung perfusion. PMID:18544813

  9. FEM convergence of a segmentation approach to the electrical impedance tomography problem

    NASA Astrophysics Data System (ADS)

    Mendoza, Renier; Keeling, Stephen

    2016-02-01

    In Electrical Impedance Tomography (EIT), different current patterns are injected to the unknown object through the electrodes attached at the boundary ∂ Ω of Ω. The corresponding voltages V are then measured on its boundary surface. Based on these measured voltages, the image reconstruction of the conductivity distribution σ is done by solving an inverse problem of a generalized Laplace equation subject to a homogeneous Neumann boundary condition. In other words, with known V, we seek to solve for the typically piecewise values of σ, from which the geometry of internal objects may be inferred. We approach this problem by using a multi-phase segmentation method. We express σ as σ (x)= ∑m=1Mσm(x)χm (x) , where χm is the characteristic function of a subdomain Ωm such that Ωm ∩ Ωn = Ø, m ≠ n and Ω= ∪m=1MΩm. The expected number of phases for Ω is M, where M = 2 for this work. The number of segments is the number of connected components of the subdomains. Using a calculated optimality condition, the conductivity value σm is expressed as a function of χm. The total variation of χm is then introduced to regularize the resulting cost functional. Using a descent method, an update for χm is proposed. In this work, the Finite Element Method (FEM) convergence of all the resulting variational formulations are studied. A real analytic mollification of χm is introduced to guarantee convergence.

  10. Spaceflight and hind limb unloading induce similar changes in electrical impedance characteristics of mouse gastrocnemius muscle

    PubMed Central

    Sung, M.; Li, J.; Spieker, A.J.; Spatz, J.; Ellman, R.; Ferguson, V.L.; Bateman, T.A.; Rosen, G.D.; Bouxsein, M.; Rutkove, S.B.

    2014-01-01

    Objective To assess the potential of electrical impedance myography (EIM) to serve as a marker of muscle fiber atrophy and secondarily as an indicator of bone deterioration by assessing the effects of spaceflight or hind limb unloading. Methods In the first experiment, 6 mice were flown aboard the space shuttle (STS-135) for 13 days and 8 earthbound mice served as controls. In the second experiment, 14 mice underwent hind limb unloading (HLU) for 13 days; 13 additional mice served as controls. EIM measurements were made on ex vivo gastrocnemius muscle. Quantitative microscopy and areal bone mineral density (aBMD) measurements of the hindlimb were also performed. Results Reductions in the multifrequency phase-slope parameter were observed for both the space flight and HLU cohorts compared to their respective controls. For ground control and spaceflight groups, the values were 24.7±1.3°/MHz and 14.1±1.6°/MHz, respectively (p=0.0013); for control and HLU groups, the values were 23.9±1.6°/MHz and 19.0±1.0°/MHz, respectively (p=0.014). This parameter also correlated with muscle fiber size (ρ=0.65, p=0.011) for spaceflight and hind limb aBMD (ρ=0.65, p=0.0063) for both groups. Conclusions These data support the concept that EIM may serve as a useful tool for assessment of muscle disuse secondary to immobilization or microgravity. PMID:24292610