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Sample records for electrical impedance measurement

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. Measurement of limb blood flow by electrical impedance plethysmography.

    PubMed Central

    Porter, J. M.; Swain, I. D.; Shakespeare, P. G.

    1985-01-01

    Limb blood flow has been measured in 72 individuals by the noninvasive technique of electrical impedance plethysmography. Venous occlusion was not used. Blood flow was measured in 230 limbs in which 195 limbs were either in normal individuals or the clinically normal limbs of patients (normal limbs). Thirty-five limbs were clinically abnormal. Measurements on limbs with clinical abnormalities showed that blood flow values often fell within the limits of the normal range. However 3 cases of known vascular injury and 2 cases studied after hand surgery under tourniquet showed lowered blood flow values by comparison with the unaffected limb. A simultaneously recorded range of cardiac output and stroke volume measurements gave similar results to those obtained in a previous, unconnected study. Images Fig. 1 PMID:4004047

  6. 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)

  7. A two electrode apparatus for electrical impedance measurements

    NASA Astrophysics Data System (ADS)

    Merriam, J. B.

    2009-12-01

    A two electrode cell for complex impedance measurements on core samples in the range 1 mHz - 0.3 kHz is described. Two electrode cells are more convenient than four electrode cells but some restrictions need to be observed. I will show that the contact impedance between the electrodes and the sample can be controlled and reduced to less than fifty ohms in most cases. The contact impedance is repeatable, with a peak phase near 10 Hz of less than one degree and a maximum change in impedance magnitude of less than fifty ohm. A model for the contact impedance is used to correct impedance measurements, leaving an un-modeled contact impedance of a few ohms. There is typically a drift of about 100 ohm during a measurement sequence due to diffusion between the ceramic frits at the ends of the sample. This is corrected by repeat measurements at 100 Hz. Un-modeled impedance changes due to drift are about ten ohm. The un-modeled impedance changes mean that the relative error on conductive samples is greater than on resistive samples. Repeat measurements on a sandstone sample with conductive pore water (0.14 S/m) yield a mean of 492 ohms with a standard deviation of 20 ohm, or about five percent. Measurements on mineralized core and on cells constructed from mixtures of silica sand and polarizable minerals demonstrate that the two electrode set up can be used even on heavily mineralized samples.

  8. In-Vivo Electrical Impedance Measurement in Mastoid Bone.

    PubMed

    Wyss Balmer, Thomas; Ansó, Juan; Muntane, Enric; Gavaghan, Kate; Weber, Stefan; Stahel, Andreas; Büchler, Philippe

    2017-04-01

    Nerve monitoring is a safety mechanism to detect the proximity between surgical instruments and important nerves during surgical bone preparation. In temporal bone, this technique is highly specific and sensitive at distances below 0.1 mm, but remains unreliable for distances above this threshold. A deeper understanding of the patient-specific bone electric properties is required to improve this range of detection. A sheep animal model has been used to characterize bone properties in vivo. Impedance measurements have been performed at low frequencies (<1 kHz) between two electrodes placed inside holes drilled into the sheep mastoid bone. An electric circuit composed of a resistor and a Fricke constant phase element was able to accurately describe the experimental measurements. Bone resistivity was shown to be linearly dependent on the inter-electrode distance and the local bone density. Based on this model, the amount of bone material between the electrodes could be predicted with an error of 0.7 mm. Our results indicate that bone could be described as an ideal resistor while the electrochemical processes at the electrode-tissue interface are characterized by a constant phase element. These results should help increasing the safety of surgical drilling procedures by better predicting the distance to critical nerve structures.

  9. A multichannel continuously selectable multifrequency electrical impedance spectroscopy measurement system.

    PubMed

    Hartov, A; Mazzarese, R A; Reiss, F R; Kerner, T E; Osterman, K S; Williams, D B; Paulsen, K D

    2000-01-01

    There is increasing evidence that alterations in the electrical property spectrum of tissues below 10 MHz is diagnostic for tissue pathology and/or pathophysiology. Yet, the complexity associated with constructing a high-fidelity multichannel, multifrequency data acquisition instrument has limited widespread development of spectroscopic electrical impedance imaging concepts. To contribute to the relatively sparse experience with multichannel spectroscopy systems this paper reports on the design, realization and evaluation of a prototype 32-channel instrument. The salient features of the system include a continuously selectable driving frequency up to 1 MHz, either voltage or current source modes of operation and simultaneous measurement of both voltage and current on each channel in either of these driving configurations. Comparisons of performance with recently reported fixed-frequency systems is favorable. Volts dc (VDC) signal-to-noise ratios of 75-80 dB are achieved and the noise floor for ac signals is near 100 dB below the signal strength of interest at 10 kHz and 60 dB down at 1 MHz. The added benefit of being able to record multispectral information on source and sense signal amplitudes and phases has also been realized. Phase-sensitive detection schemes and multiperiod undersampling techniques have been deployed to ensure measurement fidelity over the full bandwidth of system operation.

  10. 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

  11. 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.

  12. Magnetic resonance electrical impedance tomography for measuring electrical conductivity during electroporation.

    PubMed

    Kranjc, M; Bajd, F; Serša, I; Miklavčič, D

    2014-06-01

    The electroporation effect on tissue can be assessed by measurement of electrical properties of the tissue undergoing electroporation. The most prominent techniques for measuring electrical properties of electroporated tissues have been voltage-current measurement of applied pulses and electrical impedance tomography (EIT). However, the electrical conductivity of tissue assessed by means of voltage-current measurement was lacking in information on tissue heterogeneity, while EIT requires numerous additional electrodes and produces results with low spatial resolution and high noise. Magnetic resonance EIT (MREIT) is similar to EIT, as it is also used for reconstruction of conductivity images, though voltage and current measurements are not limited to the boundaries in MREIT, hence it yields conductivity images with better spatial resolution. The aim of this study was to investigate and demonstrate the feasibility of the MREIT technique for assessment of conductivity images of tissues undergoing electroporation. Two objects were investigated: agar phantoms and ex vivo liver tissue. As expected, no significant change of electrical conductivity was detected in agar phantoms exposed to pulses of all used amplitudes, while a considerable increase of conductivity was measured in liver tissue exposed to pulses of different amplitudes.

  13. Theory and cardiac applications of electrical impedance measurements.

    PubMed

    Penney, B C

    1986-01-01

    The methodology of the two-electrode, four-electrode, and guard-ring techniques is presented following a brief history of impedance plethysmography. The theoretical basis for predicting the sampling fields for conductivity and volume changes is presented. Theoretical and experimental studies of the sampling field associated with various electrode arrays are reviewed. With this background, the use of impedance plethysmography for cardiac monitoring and diagnosis is reviewed. The basic methodology is presented and models used to interpret the signal are reviewed. Theoretical and experimental studies of what is sampled are summarized. The accuracy of impedance stroke volume estimates is evaluated by surveying the results of human studies and examining critical animal studies. The usefulness of impedance cardiography for ventricular performance evaluation is also reviewed. Additional uses for cardiopulmonary diagnosis are briefly presented.

  14. Non-Contact Measurement of the Electrical Impedance of Biological Tissue

    DTIC Science & Technology

    2007-11-02

    NON-CONTACT MEASUREMENT OF THE ELECTRICAL IMPEDANCE OF BIOLOGICAL TISSUE C.H. Riedel and O.Dössel Institute of Biomedical Engineering, Universität...currents. Keywords—contact-free measurement, electrical im- pedance, coil systems I. Introduction The non-invasive method of measuring the impe- dance...can give information of the electrical characte- ristics of tissue. In some cases the conductivity gra- dient can be an important value. The

  15. Piezo-sensor self-diagnostics using electrical impedance measurements.

    SciTech Connect

    Park, G. H.; Farrar, C. R.; Rutherford, A. C.; Robertson, A. N.

    2004-01-01

    This paper present the piezoelectric sensor self-diagnostic procedure that performs in-situ monitoring of the operational status of piezoelectric materials (PZT) used for sensors and actuators in structural health monitoring (SHM) applications. The use of active-sensing piezoelectric materials has received considerable attention in the SHM community. A critical aspect of the piezoelectric active-sensing technologies is that usually large numbers of distributed sensors and actuators are needed to perform the required monitoring process. The sensor/actuator self-diagnostic procedure, where the sensors/actuators are confirmed to be functioning properly during operation, is therefore a critical component to successfully complete the SHM process and to minimize the false indication regarding the structural health. The basis of this procedure is to track the changes in the capacitive value of piezoelectric materials resulting from the sensor failure, which is manifested in the imaginary part of the measured electrical admittances. Furthermore, through the analytical and experimental investigation, it is confirmed that the bonding layer between the PZT and a host structure significantly contributes to the measured capacitive values. Therefore, by monitoring the imaginary part of the admittances, one can quantitatively assess the degradation of the mechanical/electrical properties of the PZT and its attachment to a host structure. This paper concludes with an experimental example to demonstrate the feasibility of the proposed sensor-diagnostic procedure.

  16. 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

  17. Drilling electrode for real-time measurement of electrical impedance in bone tissues.

    PubMed

    Dai, Yu; Xue, Yuan; Zhang, Jianxun

    2014-03-01

    In order to prevent possible damages to soft tissues, reliable monitoring methods are required to provide valuable information on the condition of the bone being cut. This paper describes the design of an electrical impedance sensing drill developed to estimate the relative position between the drill and the bone being drilled. The two-electrode method is applied to continuously measure the electrical impedance during a drill feeding movement: two copper wire brushes are used to conduct electricity in the rotating drill and then the drill is one electrode; a needle is inserted into the soft tissues adjacent to the bone being drilled and acts as another electrode. Considering that the recorded electrical impedance is correlated with the insertion depth of the drill, we theoretically calculate the electrode-tissue contact impedance and prove that the rate of impedance change varies considerably when the drill bit crosses the boundary between two different bone tissues. Therefore, the rate of impedance change is used to determine whether the tip of the drill is located in one of cortical bone, cancellous bone, and cortical bone near a boundary with soft tissue. In vitro experiments in porcine thoracic spines were performed to demonstrate the feasibility of the impedance sensing drill. The experimental results indicate that the drill, used with the proposed data-processing method, can provide accurate and reliable breakthrough detection in the bone-drilling process.

  18. 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

  19. 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

  20. 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.

  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. An analysis of electrical impedance measurements applied for plant N status estimation in lettuce (Lactuca sativa).

    PubMed

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

    2014-06-27

    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.

  3. Transthoracic electrical impedance during external defibrillation: comparison of measured and modelled waveforms.

    PubMed

    Al Hatib, F; Trendafilova, E; Daskalov, I

    2000-02-01

    The transthoracic electrical impedance is an important defibrillation parameter, affecting the defibrillating current amplitude and energy, and therefore the defibrillation efficiency. A close relationship between transthoracic impedance and defibrillation success rate was observed. Pre-shock measurements (using low amplitude high frequency current) of the impedance were considered a solution for selection of adequate shock voltages or for current-based defibrillation dosage. A recent approach, called 'impedance-compensating defibrillation' was implemented, where the pulse duration was controlled with respect to the impedance measured during the initial phase of the shock. These considerations raised our interest in reassessment of the transthoracic impedance characteristics and the corresponding measurement methods. The purpose of this work is to study the variations of the transthoracic impedance by a continuous measurement technique during the defibrillation shock and comparing the data with results obtained by modelling. Voltage and current impulse waveforms were acquired during cardioversion of patients with atrial fibrillation or flutter. The same type of defibrillation pulse was taken from dogs after induction of fibrillation. The electrodes were located in the anterior position, for both the patients and animals.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

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

    PubMed

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

    2008-09-02

    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.

  9. 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.

  10. Electrical impedance string probes for two-phase void and velocity measurements. [PWR

    SciTech Connect

    Hardy, J E; Hylton, J O

    1982-05-01

    An instrumentation scheme has been developed to measure two-phase flow velocity and void fraction during the refill/reflood stages of a loss-of-coolant accident in experimental test facilities. The instrumentation's principle of operation was based on measurement of the electrical impedance of two-phase mixtures. Two-phase velocity is estimated by time-of-flight analysis of signals from two spatially separate sensors. A relative capacitive technique was employed to measure void fraction. The impedance sensor consists of a pair of stainless steel wires strung back and forth across a stainless steel frame. This sensor was dubbed string probe for this reason. The string probe was designed to withstand temperatures of 350/sup 0/C, thermal transients of approx. 300/sup 0/C/s, and severe fluid- and condensation-induced shocks.

  11. Investigation of critical shear stress with simultaneous measurement of electrical impedance, capacitance and light backscattering.

    PubMed

    Lee, Byoung-Kwon; Ko, Jae-yong; Lim, Hyun-jung; Nam, Jeong-Hun; Shin, Sehyun

    2012-01-01

    Recent electrical investigation of hemorheology provided useful information on the kinetics of red blood cell (RBC) aggregation. However, because of the inconsistent results in the electrical measurements, we need to understand the electrical characteristics of RBC aggregation at various flow conditions. In the present study, AC electrical-capacitance (EC) and -impedance (EI) and light backscattering (LB) were simultaneously measured for transient shear-decreasing blood flow in a microchannel. EI, EC and LB signals of RBCs in plasma show similar time-varying curves, both yielding either a peak or a minimal point in the optimal frequency range (10~500 kHz). Critical shear stress (CSS) determined from EC showed the nearly same results as that determined from LB, with yielding hematocrits-independence and dextran-concentration dependence. However, the high concentration of fibrinogen caused electrical saturation, which resulted in different results of CSS determined from between LB and EC. These results suggest that electrical properties of RBC suspensions should be further examined to replace the optical method of measurement of RBC aggregation.

  12. Simulation method for cardiac stroke volume estimation by intracardiac electrical impedance measurement.

    PubMed

    Barak, C; Leviatan, Y; Inbar, G F; Hoekstein, K N

    1992-09-01

    Using the electrical impedance measurement technique to investigate stroke volume estimation, three models of the ventricle were simulated. A four-electrode impedance catheter was used; two electrodes to set up an electric field in the model and the other two to measure the potential difference. A new approach, itself an application of the quasi-static case of a method used to solve electromagnetic field problems, was used to solve the electric field in the model. The behaviour of the estimation is examined with respect to the electrode configuration on the catheter and to catheter location with respect to the ventricle walls. Cardiac stroke volume estimation was found to be robust to catheter location generating a 10 per cent error for an offset of 40 per cent of the catheter from the chamber axis and rotation of 20 degrees with respect to the axis. The electrode configuration has a dominant effect on the sensitivity and accuracy of the estimation. Certain configurations gave high accuracy, whereas in others high sensitivity was found with lower accuracy. This led to the conclusion that the electrode configuration should be carefully chosen according to the desired criteria.

  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 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.

  15. Electrical-Impedance Tomography for Measuring Material Distributions of Multiphase Flows in Conducting Vessels

    NASA Astrophysics Data System (ADS)

    Liter, S. G.; Torczynski, J. R.; Shollenberger, K. A.; Ceccio, S. L.

    2001-11-01

    An implementation of resistive electrical-impedance tomography (EIT) for measuring material distributions of two-phase flows in vessels with electrically conducting walls is presented. A thin nonconducting rod, with N-1 ring electrodes wrapped around its exterior at equally-spaced axial positions, is inserted into the vessel (i.e., into the interior of the flow). The vessel wall is grounded and serves as the N-th electrode. Current is injected from a ring electrode and exits to the vessel wall, and the resulting voltages at all ring electrodes are recorded. Each ring electrode is used in turn for current injection, and the collection of all measured voltages comprises a data set. Multiple data sets are used to numerically reconstruct the time-averaged impedance distribution within the vessel, from which the material distribution is inferred. Design issues, including the size, spacing, and number of the ring electrodes, are considered. An experiment in which the rod is inserted coaxially into a vertical pipe is presented, and bubble-column applications are discussed. *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

  16. 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

  17. 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.

  18. Modification of polysulfone membranes with polyethylene glycol and lignosulfate: electrical characterization by impedance spectroscopy measurements.

    PubMed

    Benavente, J; Zhang, X; Garcia Valls, R

    2005-05-01

    Two sets of composite membranes having an asymmetric sulfonated polysulfone membrane as support layer have been obtained and electrically characterized (membranes SPS-PEG and PA-LIGS). The skin layer of the membrane SPS-PEG contains different percentages of polyethylene glycol in the casting solution (5, 25, 40, and 60 wt%), while lignosulfonate was used for manufacturing PA-LIGS membranes (5, 10, 20, and 40 wt%). Membrane electrical characterization was done by means of impedance spectroscopy (IS) measurements, which were carried out with the membranes in contact with NaCl solutions at different concentrations (10(-3) < or = c(M) < or = 5x10(-2)). Electrical resistance and equivalent capacitance of the different membrane samples were determined from IS plots by using equivalent circuits as models. Results show a clear decrease in the membrane electrical resistance as a result of both polysulfone sulfonation and the increase of the concentration of modifying substances, although a kind of limit concentration was obtained for both polyethylene glycol and lignosulfonate (40 and 20%, respectively). Results also show a decrease of around 90% in electrical resistance due to polysulfone sulfonation, while the value of the dielectric constant (hydrated state) clearly increases.

  19. 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.

  20. 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

  1. Vertical impedance measurements of concrete bridge deck cover condition without a direct electrical connection to the reinforcing steel

    NASA Astrophysics Data System (ADS)

    Mazzeo, Brian A.; Baxter, Jared; Barton, Jeffrey; Guthrie, W. Spencer

    2017-02-01

    Vertical impedance measurements provide significant quantitative information about the ability of concrete cover to slow the penetration of chloride ions that can corrode steel reinforcement in a bridge deck. The primary limitations preventing the widespread adoption of vertical impedance for assessment of concrete bridge decks are (1) the necessity to have a direct electrical connection to the embedded steel reinforcement and (2) the low speeds of data acquisition. This work presents solutions to both limitations. A method using a large-area electrode as a reference electrode for vertical impedance testing is validated using both simulations and measurements in the field.

  2. 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.

  3. 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.

  4. Electrical properties of rat muscle after sciatic nerve injury: Impact on surface impedance measurements assessed via finite element analysis

    NASA Astrophysics Data System (ADS)

    Ahad, M. A.; Rutkove, S. B.

    2010-04-01

    Tetrapolar surface electrical impedance methods are sensitive to changes in muscle status and can therefore provide a means for studying neuromuscular disease noninvasively. In order to better understand the relationship between surface impedance measurements and the actual muscle electrical properties, we performed measurements on 20 adult Wistar rats, 8 of which underwent sciatic nerve crush. Surface impedance measurements were performed on the left hind limb both before injury and out to 2 weeks after injury. In addition, both normal and sciatic crush animals were sacrificed and the dielectric properties of the extracted gastrocnemius muscle measured. We found that 50 kHz conductivities were greater in the animals that underwent crush than in the animals that did not. The permittivities in both directions, however, showed non-significant differences. In order to analyze the effect of these changes as well as the accompanying reduction in muscle volume, a finite element model of the hind limb was developed based on computerized tomographic imaging. The model successfully predicted the surface impedance values in the animals after crush injury and, by its inverse application, may be used to help determine the underlying electrical properties of muscle in various neuromuscular diseases based on surface impedance data.

  5. Measuring the electric properties of planetary environments with Mutual Impedance (MI) Probes

    NASA Astrophysics Data System (ADS)

    Trautner, R.; Grard, R.

    2002-10-01

    Mutual Impedance Probes measure the complex permittivity of material by means of a quadrupolar array of electrodes and associated electronics for generating, recording and processing waveforms. MI instruments have been developed for a number of ongoing space missions. The HASI/PWA MI probe will determine the electric properties of the atmosphere of Titan, Saturn's largest moon, during the descent of the Huygens probe. After landing, the instrument will provide data on the properties of Titan's surface materials. The permittivity probe PP, as part of the SESAME instrument package for the Rosetta Lander, will determine the electrical properties of comet Wirtanen's surface. The main features of MI probes are first recapitulated. Instrument architectures for atmospheric, surface and subsurface investigations are described. Results from recent field test campaigns in harsh environments are presented. A new MI probe prototype employing a linear electrode array for application on mobile platforms or on penetrator devices is described. New application areas for future MI probes and relevant technology requirements are discussed.

  6. Measuring The Electric Properties of Planetary Surface Materials With Mutual Impedance (mi) Probes

    NASA Astrophysics Data System (ADS)

    Trautner, R.; Grard, R.

    Mutual Impedance Probes have been developed for a number of ongoing space mis- sions. The HASI/PWA MI probe will determine the electric properties of the atmo- sphere and surface of Saturn's largest moon, Titan, in 2004. The Permittivity Probe of the SESAME instrument package on the Rosetta Lander will attempt to measure the conductivity and permittivity of the cometary surface material. While both instruments have similar objectives, their architecture (design and integration into the spacecraft, electrode geometry) and properties (measurement range and precision) differ signif- icantly. The main features of the Huygens PWA and Rosetta Lander SESAME MI probes are first recapitulated and their expected performances are assessed. A new MI probe prototype employing a linear electrode array for application on mobile platforms or penetrator devices is then described. Results from a recent field test campaign in the Australian desert are presented and the prototype performance is evaluated. New application areas for future MI probes and relevant technology requirements are dis- cussed.

  7. Tissue electrical properties measured by bioelectrical impedance analysis among healthy and sportsmen population

    NASA Astrophysics Data System (ADS)

    Kapica, Dominik; Warchulińska, Joanna; Jakubiak, Monika; Teter, Mariusz; Mlak, Radosław; Hałabiś, Magdalena; Wójcik, Waldemar; Małecka-Massalska, Teresa

    2015-09-01

    Introduction: Bioelectrical impedance analysis (BIA) is a useful tool to asses human body composition and nutrition status; multi-frequency BIA has a higher accuracy than single-frequency BIA. In our study a difference of impedance values (Z) at 5, 100 and 200 kHz and Z200/Z5 index between professional athletes and control group were determined. Methods: In this research 105 people were tested, divided into control group (72 people: 35 males and 37 females) and professional athletes (33 people: 16 males and 17 females). Impedance was measured at three frequency values - 5, 100 and 200 kHz; with received values the Z200/Z5 index was calculated. Results: In most compared subgroups impedance values showed significantly lower values in athletes than in control group (5 kHz - males: p=0.136, females: p=0.001, 100 kHz - males: p=0.039, females: p<0.0001, 200 kHz - males: p=0.047, females: p<0.0001) Z200/Z5 index also showed lower value in athletes than in control group (p=0.016 for males, p<0.0001 for females). Conclusion: Lower values of impedance and Z200/Z5 index indicates a better nutrition status and general health condition of athletes than in control group.

  8. 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.

  9. 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.

  10. 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)

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

    PubMed Central

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

    2008-01-01

    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

  12. 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.

  13. 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.

  14. 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

  15. In vivo and in situ measurement of electrical impedance for determination of distention in proximal stomach of rats.

    PubMed

    Garay, L; Ramos, E G; Cardiel, E; Muñoz, R; Hernández, P R

    2006-09-01

    We present a non-invasive, in vivo and in situ study of proximal stomach (PS) distention based on electrical impedance measurements that could be used together with distal stomach (DS) motility measurements as a response to different boluses. Stomach motility has been reported in the literature, as a response to different boluses, under in vivo conditions. However, previous studies on stomach motility have been mainly considered clinical parameters of the digestive process. The physiological complexity of the stomach requires the use of biological models when a detailed analysis of stomach function due to bolus ingestion is required. In this work, the determination of the PS distention in rats is presented. It is based on electrical resistive impedance measurements of the external stomach wall, related to different liquid bolus volumes. Trials were performed under in vivo and in situ conditions. A four-point technique with a vacuum-affixed linear electrode array was used for impedance measurements. A pouch was created in the stomach to retain the saline solution bolus in the PS for a longer time. Resulting impedance changes were directly related to the bolus volumes introduced into the PS and dependent on initial conditions and compensation mechanisms of the in vivo system. With the stomach pouch, a direct relationship between resistive impedance and bolus volume was obtained in all measurements. With no stomach pouch, 93% of the cases showed this relationship. Therefore, the obtained relationship will permit new non-invasive studies in the stomach about the effects of different types of bolus on the distention in the PS of rats.

  16. Investigation of potential artefactual changes in measurements of impedance changes during evoked activity: implications to electrical impedance tomography of brain function.

    PubMed

    Aristovich, Kirill Y; Dos Santos, Gustavo S; Holder, David S

    2015-06-01

    Electrical impedance tomography (EIT) could provide images of fast neural activity in the adult human brain with a resolution of 1 ms and 1 mm by imaging impedance changes which occur as ion channels open during neuronal depolarization. The largest changes occur at dc and decrease rapidly over 100 Hz. Evoked potentials occur in this bandwidth and may cause artefactual apparent impedance changes if altered by the impedance measuring current. These were characterized during the compound action potential in the walking leg nerves of Cancer pagurus, placed on Ag/AgCl hook electrodes, to identify how to avoid artefactual changes during brain EIT. Artefact-free impedance changes (δZ) decreased with frequency from -0.045 ± 0.01% at 225 Hz to -0.02 ± 0.01% at 1025 Hz (mean ± 1 SD, n = 24 in 12 nerves) which matched changes predicted by a finite element model. Artefactual δZ reached c.300% and 50% of the genuine membrane impedance change at 225 Hz and 600 Hz respectively but decreased with frequency of the applied current and was negligible above 1 kHz. The proportional amplitude (δZ (%)) of the artefact did not vary significantly with the amplitude of injected current of 5-20 µA pp. but decreased significantly from -0.09 ± 0.024 to -0.03 ± 0.023% with phase of 0 to 45°. For fast neural EIT of evoked activity in the brain, artefacts may arise with applied current of >10 µA. Independence of δZ with respect to phase but not the amplitude of applied current controls for them; they can be minimized by randomizing the phase of the applied measuring current and excluded by recording at >1 kHz.

  17. 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.

  18. 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.

  19. Impedance Measurement Box

    SciTech Connect

    Morrison, William

    2014-11-20

    The IMB 50V software provides functionality for design of impedance measurement tests or sequences of tests, execution of these tests or sequences, processing measured responses and displaying and saving of the results. The software consists of a Graphical User Interface that allows configuration of measurement parameters and test sequencing, a core engine that controls test sequencing, execution of measurements, processing and storage of results and a hardware/software data acquisition interface with the IMB hardware system.

  20. A systematic investigation into the electrical properties of single HeLa cells via impedance measurements and COMSOL simulations.

    PubMed

    Wang, Min-Haw; Jang, Ling-Sheng

    2009-05-15

    The electrical properties of single cells provide fundamental insights into their pathological condition and are therefore of immense interest to medical practitioners. Accordingly, this study captures single HeLa cells using a microfluidic device and then measures their impedance properties using a commercial impedance spectroscopy system. The experimental system is modeled by an equivalent electrical circuit and COMSOL simulations are then performed to establish the conductivity, permittivity and impedance of single HeLa cells under various operational frequencies and voltages. At an operational voltage of 0.2 V, the maximum deviation between the experimental and simulation results for the magnitude and phase of the HeLa cell impedance is found to be 9.5% and 4.2%, respectively. In general, both sets of results show that the conductivity and permittivity of single HeLa cells increase with an increasing operational voltage. Moreover, an increasing frequency is found to increase the conductivity of HeLa cells at all values of the operational voltage, but to reduce the permittivity for operational voltages in the range 0.6-1.0 V. Based upon the simulation and experimental results, empirical equations are constructed to predict the conductivity and permittivity of single HeLa cells under specified values of the operational voltage and frequency, respectively. The maximum discrepancy between the predicted results and the simulation results for the permittivity and conductivity of the HeLa cells at an operational voltage of 0.2 V is found to be just 0.5% and 4.5%, respectively.

  1. FEM electrode refinement for electrical impedance tomography.

    PubMed

    Grychtol, Bartlomiej; Adler, Andy

    2013-01-01

    Electrical Impedance Tomography (EIT) reconstructs images of electrical tissue properties within a body from electrical transfer impedance measurements at surface electrodes. Reconstruction of EIT images requires the solution of an inverse problem in soft field tomography, where a sensitivity matrix, J, of the relationship between internal changes and measurements is calculated, and then a pseudo-inverse of J is used to update the image estimate. It is therefore clear that a precise calculation of J is required for solution accuracy. Since it is generally not possible to use analytic solutions, the finite element method (FEM) is typically used. It has generally been recommended in the EIT literature that FEMs be refined near electrodes, since the electric field and sensitivity is largest there. In this paper we analyze the accuracy requirement for FEM refinement near electrodes in EIT and describe a technique to refine arbitrary FEMs.

  2. Impedance Measurement Box

    ScienceCinema

    Christophersen, Jon

    2016-07-12

    Energy storage devices, primarily batteries, are now more important to consumers, industries and the military. With increasing technical complexity and higher user expectations, there is also a demand for highly accurate state-of-health battery assessment techniques. IMB incorporates patented, proprietary, and tested capabilities using control software and hardware that can be part of an embedded monitoring system. IMB directly measures the wideband impedance spectrum in seconds during battery operation with no significant impact on service life. It also can be applied to batteries prior to installation, confirming health before entering active service, as well as during regular maintenance. For more information about this project, visit http://www.inl.gov/rd100/2011/impedance-measurement-box/

  3. Constant current loop impedance measuring system that is immune to the effects of parasitic impedances

    NASA Technical Reports Server (NTRS)

    Anderson, Karl F. (Inventor)

    1994-01-01

    A constant current loop measuring system is provided for measuring a characteristic of an environment. The system comprises a first impedance positionable in the environment, a second impedance coupled in series with said first impedance and a parasitic impedance electrically coupled to the first and second impedances. A current generating device, electrically coupled in series with the first and second impedances, provides a constant current through the first and second impedances to produce first and second voltages across the first and second impedances, respectively, and a parasitic voltage across the parasitic impedance. A high impedance voltage measuring device measures a voltage difference between the first and second voltages independent of the parasitic voltage to produce a characteristic voltage representative of the characteristic of the environment.

  4. Electrical Impedance Tomography of Breast Cancer

    DTIC Science & Technology

    2005-06-01

    SUBJECT TERMS Diagnosis of Metastatic Cancer, Magnetic Resonance Imaging, Electrical Impedance Imaging, Electrical Impedance Scanning, MRI current...1) To develop and optimize the necessary hardware and software for Magnetic Resonance Electrical Impedance Tomography (MREIT) and interface it with...of Magnetic Resonance in Medicine (ISMRM) conference and included in the appendix for reference. 2.2.2. Second Year: A series of new phantom studies

  5. The possible use of combined electrical impedance and ultrasound velocity measurements for the non-invasive measurement of temperature during mild hyperthermia.

    PubMed

    Islam, Naimul; Hale, Rebecca; Taylor, Matthew; Wilson, Adrian

    2013-09-01

    This paper explores the possibility of using combined measurements of electrical impedance and changes in ultrasound time of flight for determining deep body temperature during mild hyperthermia. Simultaneous electrical impedance spectra (1 kHz-1024 kHz) and ultrasound time-of-flight measurements were made on layered sheep liver and fat tissue samples as the temperature was increased from 30-50 °C. The change in propagation velocity for 100% fat and 100% liver samples was found to vary linearly with temperature and the temperature coefficient of the time-of-flight was shown to vary linearly with the % fat in the sample (0.009% °C-1%-1). Tetrapolar impedance measurements normalized to 8 kHz were shown to have a small sensitivity to temperature for both liver (0.001% °C-1 ≤ 45 °C) and fat (0.002% °C-1 ≤ 512 kHz) and the best linear correlation between the normalized impedance and the % fat in the sample was found at 256 kHz (gradient 0.026%-1, r2 = 0.65). A bootstrap analysis on 15 layered tissue samples evaluated using the normalized impedance at 256 kHz to determine the % fat in the sample and the temperature coefficient of the time of flight to determine the temperature. The results showed differences (including some large differences) between the predicted and measured temperatures and an error evaluation identified the possible origins of these.

  6. Electrical impedance tomography of electrolysis.

    PubMed

    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.

  7. Monolithically compatible impedance measurement

    DOEpatents

    Ericson, Milton Nance; Holcomb, David Eugene

    2002-01-01

    A monolithic sensor includes a reference channel and at least one sensing channel. Each sensing channel has an oscillator and a counter driven by the oscillator. The reference channel and the at least one sensing channel being formed integrally with a substrate and intimately nested with one another on the substrate. Thus, the oscillator and the counter have matched component values and temperature coefficients. A frequency determining component of the sensing oscillator is formed integrally with the substrate and has an impedance parameter which varies with an environmental parameter to be measured by the sensor. A gating control is responsive to an output signal generated by the reference channel, for terminating counting in the at least one sensing channel at an output count, whereby the output count is indicative of the environmental parameter, and successive ones of the output counts are indicative of changes in the environmental parameter.

  8. Electrical impedance spectroscopy and diagnosis of tendinitis.

    PubMed

    Yoon, Kisung; Lee, Kyeong Woo; Kim, Sang Beom; Han, Tai Ryoon; Jung, Dong Keun; Roh, Mee Sook; Lee, Jong Hwa

    2010-02-01

    There have been a number of studies that investigate the usefulness of bioelectric signals in diagnoses and treatment in the medical field. Tendinitis is a musculoskeletal disorder with a very high rate of occurrence. This study attempts to examine whether electrical impedance spectroscopy (EIS) can detect pathological changes in a tendon and find the exact location of the lesion. Experimental tendinitis was induced by injecting collagenase into one side of the patellar tendons in rabbits, while the other side was used as the control. After measuring the impedance in the tendinitis and intact tendon tissue, the dissipation factor was computed. The real component of impedance and the dissipation factor turned out to be lower in tendinitis than in intact tissues. Moreover, the tendinitis dissipation factor spectrum showed a clear difference from that of the intact tendon, indicating its usefulness as a tool for detecting the location of the lesion. Pathologic findings from the tissues that were obtained after measuring the impedance confirmed the presence of characteristics of tendinitis. In conclusion, EIS is a useful method for diagnosing tendinitis and detecting the lesion location in invasive treatment.

  9. Acoustic impedance measurements of pulse tube refrigerators

    NASA Astrophysics Data System (ADS)

    Iwase, Takashi; Biwa, Tetsushi; Yazaki, Taichi

    2010-02-01

    Complex acoustic impedance is determined in a prototype refrigerator that can mimic orifice-type, inertance-type, and double inlet-type pulse tube refrigerators from simultaneous measurements of pressure and velocity oscillations at the cold end. The impedance measurements revealed the means by which the oscillatory flow condition in the basic pulse tube refrigerator is improved by additional components such as a valve and a tank. The working mechanism of pulse tube refrigerators is explained based on an electrical circuit analogy.

  10. Broadband electrical impedance matching for piezoelectric ultrasound transducers.

    PubMed

    Huang, Haiying; Paramo, Daniel

    2011-12-01

    This paper presents a systematic method for designing broadband electrical impedance matching networks for piezoelectric ultrasound transducers. The design process involves three steps: 1) determine the equivalent circuit of the unmatched piezoelectric transducer based on its measured admittance; 2) design a set of impedance matching networks using a computerized Smith chart; and 3) establish the simulation model of the matched transducer to evaluate the gain and bandwidth of the impedance matching networks. The effectiveness of the presented approach is demonstrated through the design, implementation, and characterization of impedance matching networks for a broadband acoustic emission sensor. The impedance matching network improved the power of the acquired signal by 9 times.

  11. Twelve years evolution of skin as seen by electrical impedance

    NASA Astrophysics Data System (ADS)

    Nicander, Ingrid; Emtestam, Lennart; Åberg, Peter; Ollmar, Stig

    2010-04-01

    Twelve years ago we reported an electrical impedance baseline study related to age, sex and body locations. The results showed significant differences between different anatomical locations and ages. In this study, the same participants were recalled to explore how the skin had evolved at the individual level over time. A total of 50 subjects, divided into an older and a younger group, were recalled for measurements of electrical impedance at eight anatomical locations. Readings were taken with an electrical impedance spectrometer. Information was extracted from the impedance spectra using indices based on magnitude and phase at two frequencies as in the earlier study. All included body sites had undergone alterations over time, and the size of the changes varied at different locations. The results also showed that changes in the younger group were different over time compared with the older group. In conclusion: Electrical impedance can be used to monitor skin evolution over time and baseline characteristics differ between various locations.

  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. Electrical Impedance Tomography of Breast Cancer

    DTIC Science & Technology

    2004-06-01

    Resonance Research Systems, Guildford, UK) that has broadband RF transmit and receive channels. A 16 leg, quadrature, high-pass birdcage coil with 10...metastatic cancer, magnetic resonance imaging, 43 electrical impedance imaging, electrical impedance scanning, MRI 16. PRICE CODE current density imaging...tissue with high spatial resolution, by using it in conjunction with Magnetic Resonance Imaging (MRI) to improve diagnostic accuracy of screening. For

  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. Three-dimensional electrical impedance tomography of human brain activity.

    PubMed

    Tidswell, T; Gibson, A; Bayford, R H; Holder, D S

    2001-02-01

    Regional cerebral blood flow and blood volume changes that occur during human brain activity will change the local impedance of that cortical area, as blood has a lower impedance than that of brain. Theoretically, such impedance changes could be measured from scalp electrodes and reconstructed into images of the internal impedance of the head. Electrical Impedance Tomography (EIT) is a newly developed technique by which impedance measurements from the surface of an object are reconstructed into impedance images. It is fast, portable, inexpensive, and noninvasive, but has a relatively low spatial resolution. EIT images were recorded with scalp electrodes and an EIT system, specially optimized for recording brain function, in 39 adult human subjects during visual, somatosensory, or motor activity. Reproducible impedance changes of about 0.5% occurred in 51/52 recordings, which lasted from 6 s after the stimulus onset to 41 s after stimulus cessation. When these changes were reconstructed into impedance images, using a novel 3-D reconstruction algorithm, 19 data sets demonstrated significant impedance changes in the appropriate cortical region. This demonstrates, for the first time, that significant impedance changes, which could form the basis for a novel neuroimaging technology, may be recorded in human subjects with scalp electrodes. The final images contained spatial noise and strategies to reduce this in future work are presented.

  16. An electrical impedance sensor for water level measurements in air-water two-phase stratified flows

    NASA Astrophysics Data System (ADS)

    Ko, Min Seok; Lee, Sung Yong; Lee, Bo An; Yun, Byong Jo; Kim, Kyung Youn; Kim, Sin

    2013-09-01

    We report a design of an optimized ring-type impedance sensor for water level measurements in air-water stratified flows through horizontal pipes. The ring-type sensor is optimized in view of the sensor linearity. In order to determine an optimal electrode and gap size of a ring-type sensor which generates a linear relationship between the impedance (resistance and/or reactance) and the water level, systematic numerical calculations are performed, and a ring-type impedance sensor of electrode width-to-diameter ratio 0.25 and gap-to-diameter ratio 0.2 has been selected as optimal. Lab-scale static experiments have been conducted to verify the sensor performance in terms of the linearity. Finally, this proposed sensor is installed in a horizontal loop 40 mm in diameter and roughly 5200 mm in length and measures water levels for various stratified flow conditions. The comparisons of water level measurements between the proposed sensor and the high-speed camera images post-processed by the edge detection scheme show that the maximum deviation in dimensionless water level is roughly 0.037, which corresponds to 1.5 mm over the range 40 mm.

  17. 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.

  18. Studies on Electrical behavior of Glucose using Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Juansah, Jajang; Yulianti, Wina

    2016-01-01

    In this work we report the electrical characteristics of glucose at different frequencies. We show the correlation between electrical properties (impedance, reactance, resistance and conductance) of glucose and glucose concentration. Electrical property measurements on glucose solution were performed in order to formulate the correlation. The measurements were conducted for frequencies between 50 Hz and 1 MHz. From the measurements, we developed a single-pole Cole-Cole graph as a function of glucose concentration.

  19. 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.

  20. Readout electrode assembly for measuring biological impedance

    NASA Technical Reports Server (NTRS)

    Montgomery, L. D.; Moody, D. L., Jr. (Inventor)

    1976-01-01

    The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.

  1. Study of the Electrical Impedance Scanning

    DTIC Science & Technology

    2007-11-02

    exhibit conductive changes that cause an impedance variation between cancerous ant health tissues. Since there are very few commercial devices...contribute somehow in the evaluation of the parameters involved. Keywords – Electrical Transimpedance Scanning, Breast cancer I. INTRODUCTION The...Electrical Transimpedance Scanning (ETS) is a new technique, non-invasive, non-irradiant, used in the diagnosis of breast cancer . Combined with other

  2. 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.

  3. [Experimental study on electrical impedance properties of human hepatoma cells].

    PubMed

    Fang, Yun; Tang, Zhiyuan; Zhang, Qian; Zhao, Xin; Ma, Qing

    2014-10-01

    The AC impedance of human hepatoma SMMC-7721 cells were measured in our laboratory by Agilent 4294A impedance analyzer in the frequency range of 0.01-100 MHz. And then the effect of hematocrit on electrical impedance characteristics of hepatoma cells was observed by electrical impedance spectroscopy, Bode diagram, Nyquist diagram and Nichols diagram. The results showed that firstly, there is a frequency dependence, i.e., the increment of real part and the imaginary part of complex electrical impedance (δZ', δZ"), the increment of the amplitude modulus of complex electrical impedance (δ[Z *]) and phase angle (δθ) were all changed with the increasing frequency. Secondly, it showed cell volume fraction (CVF) dependence, i. e. , the increment of low-frequency limit (δZ'0, δ[Z*] 0), peak (δZ"(p), δθ(p)), area and radius (Nyquist diagram, Nichols diagram) were all increased along with the electric field frequency. Thirdly, there was the presence of two characteristic frequencies: the first characteristic frequency (f(c1)) and the second characteristic frequency (f(c2)), which were originated respectively in the polarization effects of two interfaces that the cell membrane and extracellular fluid, cell membrane and cytoplasm. A conclusion can be drawn that the electrical impedance spectroscopy is able to be used to observe the electrical characteristics of human hepatoma cells, and therefore this method can be used to investigate the electrophysiological mechanisms of liver cancer cells, and provide research tools and observation parameters, and it also has important theoretical value and potential applications for screening anticancer drugs.

  4. Towards a self-reporting coronary artery stent--measuring neointimal growth associated with in-stent restenosis using electrical impedance techniques.

    PubMed

    Shedden, Laurie; Kennedy, Simon; Wadsworth, Roger; Connolly, Patricia

    2010-10-15

    Implantable medical devices have become the standard method for treating a variety of cardiovascular diseases (NICE, 2003, 2009), such as coronary artery disease, where coronary artery stents are the device of choice (Fischman et al., 1994; Babapulle et al., 2004). One post-operative problem with these devices is the long-term monitoring of the device-tissue interface, with respect to the complications that often arise from in-stent restenosis. This monitoring, where it is available, is currently performed using imaging techniques such as contrast angiography, IVUS, CT and MRI. In this study we propose an alternative method for the non-invasive monitoring of restenosis in coronary artery stents. This preliminary study uses impedance spectroscopy to measure the electrical impedance of cells and tissues associated with the neointimal growth that characterises in-stent restenosis in coronary artery stents. An in vitro organ culture model, using a stent implanted in a section of pig coronary artery, simulated tissue growth inside a stent. Impedance measurements were made regularly over a 28-day culture period. In a novel step, the stent itself was employed as an electrode. Differences in electrical impedance could be seen between control (stent alone) and artery-embedded stents in culture, which were associated with the presence of biological tissue. This method could potentially be developed to produce a stent that was capable of self-reporting in-stent restenosis. The advantages of such a device would be that monitoring could be non-invasively and easily carried out, allowing more routine follow-ups and the early identification and management of any device complications.

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

    PubMed

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

    2015-05-07

    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.

  6. 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.

  7. Intravascular electric impedance spectroscopy of atherosclerotic lesions using a new impedance catheter system.

    PubMed

    Süselbeck, T; Thielecke, H; Köchlin, J; Cho, S; Weinschenk, I; Metz, J; Borggrefe, M; Haase, K K

    2005-09-01

    Newer techniques are required to identify atherosclerotic lesions that are prone to rupture. Electric impedance spectroscopy (EIS) can characterize biological tissues by measuring the electrical impedance over a frequency range. We tested a newly designed intravascular impedance catheter (IC) by measuring the impedance of different stages of atherosclerosis induced in an animal rabbit model. Six female New Zealand White rabbits were fed for 17 weeks with a 5% cholesterol-enriched diet to induce early forms of atherosclerotic plaques. All aortas were prepared from the aortic arch to the renal arteries and segments of 5-10 mm were marked by ink spots. A balloon catheter system with an integrated polyimide-based microelectrode structure was introduced into the aorta and the impedance was measured at each spot by using an impedance analyzer. The impedance was measured at frequencies of 1 kHz and 10 kHz and compared with the corresponding histomorphometric data of each aortic segment.Forty-four aortic segments without plaques and 48 segments with evolving atherosclerotic lesions could be exactly matched by the histomorphometric analysis. In normal aortic segments (P0) the change of the magnitude of impedance at 1 kHz and at 10 kHz (|Z|(1 kHz) - |Z|(10 kHz), = ICF) was 208.5 +/- 357.6 Omega. In the area of aortic segments with a plaque smaller than that of the aortic wall diameter (PI), the ICF was 137.7 +/- 192.8 Omega. (P 0 vs. P I; p = 0.52), whereas in aortic segments with plaque formations larger than the aortic wall (PII) the ICF was significantly lower -22.2 +/- 259.9 Omega. (P0 vs. PII; p = 0.002). Intravascular EIS could be successfully performed by using a newly designed microelectrode integrated onto a conventional coronary balloon catheter. In this experimental animal model atherosclerotic aortic lesions showed significantly higher ICF in comparison to the normal aortic tissue.

  8. Wavelet-based multiscale analysis of bioimpedance data measured by electric cell-substrate impedance sensing for classification of cancerous and normal cells.

    PubMed

    Das, Debanjan; Shiladitya, Kumar; Biswas, Karabi; Dutta, Pranab Kumar; Parekh, Aditya; Mandal, Mahitosh; Das, Soumen

    2015-12-01

    The paper presents a study to differentiate normal and cancerous cells using label-free bioimpedance signal measured by electric cell-substrate impedance sensing. The real-time-measured bioimpedance data of human breast cancer cells and human epithelial normal cells employs fluctuations of impedance value due to cellular micromotions resulting from dynamic structural rearrangement of membrane protrusions under nonagitated condition. Here, a wavelet-based multiscale quantitative analysis technique has been applied to analyze the fluctuations in bioimpedance. The study demonstrates a method to classify cancerous and normal cells from the signature of their impedance fluctuations. The fluctuations associated with cellular micromotion are quantified in terms of cellular energy, cellular power dissipation, and cellular moments. The cellular energy and power dissipation are found higher for cancerous cells associated with higher micromotions in cancer cells. The initial study suggests that proposed wavelet-based quantitative technique promises to be an effective method to analyze real-time bioimpedance signal for distinguishing cancer and normal cells.

  9. Wavelet-based multiscale analysis of bioimpedance data measured by electric cell-substrate impedance sensing for classification of cancerous and normal cells

    NASA Astrophysics Data System (ADS)

    Das, Debanjan; Shiladitya, Kumar; Biswas, Karabi; Dutta, Pranab Kumar; Parekh, Aditya; Mandal, Mahitosh; Das, Soumen

    2015-12-01

    The paper presents a study to differentiate normal and cancerous cells using label-free bioimpedance signal measured by electric cell-substrate impedance sensing. The real-time-measured bioimpedance data of human breast cancer cells and human epithelial normal cells employs fluctuations of impedance value due to cellular micromotions resulting from dynamic structural rearrangement of membrane protrusions under nonagitated condition. Here, a wavelet-based multiscale quantitative analysis technique has been applied to analyze the fluctuations in bioimpedance. The study demonstrates a method to classify cancerous and normal cells from the signature of their impedance fluctuations. The fluctuations associated with cellular micromotion are quantified in terms of cellular energy, cellular power dissipation, and cellular moments. The cellular energy and power dissipation are found higher for cancerous cells associated with higher micromotions in cancer cells. The initial study suggests that proposed wavelet-based quantitative technique promises to be an effective method to analyze real-time bioimpedance signal for distinguishing cancer and normal cells.

  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. 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.

  12. Pulse Wave Velocity and Cardiac Output vs. Heart Rate in Patients with an Implanted Pacemaker Based on Electric Impedance Method Measurement

    NASA Astrophysics Data System (ADS)

    Soukup, Ladislav; Vondra, Vlastimil; Viščor, Ivo; Jurák, Pavel; Halámek, Josef

    2013-04-01

    The methods and device for estimation of cardiac output and measurement of pulse wave velocity simultaneously is presented here. The beat-to-beat cardiac output as well as pulse wave velocity measurement is based on application of electrical impedance method on the thorax and calf. The results are demonstrated in a study of 24 subjects. The dependence of pulse wave velocity and cardiac output on heart rate during rest in patients with an implanted pacemaker was evaluated. The heart rate was changed by pacemaker programming while neither exercise nor drugs were applied. The most important result is that the pulse wave velocity, cardiac output and blood pressure do not depend significantly on heart rate, while the stroke volume is reciprocal proportionally to the heart rate.

  13. Some stable reconstruction algorithms for electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Berryman, J. G.

    1991-07-01

    An impedance camera 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 and geophysical applications but the analysis of optimal reconstruction algorithms is still progressing. 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 method does not have the resolution of radiological methods, but is 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 to 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 variations issues raised here.

  14. A better method to define electrical chargeability from laboratory measurements of spectral impedance using a parallel Cole-Cole equivalent circuit

    NASA Astrophysics Data System (ADS)

    Enkin, R. J.

    2014-12-01

    Induced polarization (IP) is a successful electric method to identify drill targets for mineral exploration at the property scale. The Paleomagnetism and Petrophysics Laboratory at the Geological Survey of Canada makes petrophysical measurements on cylindrical rock samples, 2.5 cm diameter and 2.2 cm long. This small size has advantages, including allowing measurement of magnetic remanence with standard paleomagnetism equipment, but it is too small to allow a 4-contact electrical impedance measurement. The samples are impregnated with distilled water under vacuum and allowed 24 hours for solutes to dissolve off pore walls, in order to approximate original groundwater ionic conductivity. We use graphite electrodes on the flat surfaces and measure the complex impedance at 5 frequencies per decade from 1 MHz down to 25 mHz. Typical responses on a Cole-Cole plot (i.e., real vs. imaginary components displayed parametrically as a function of frequency) look like a two overlapping circular arcs followed by a constant-phase diffusive response at lowest frequencies. The impedance frequency response is fit with a circuit in which the rock is modelled as a set of parallel resistor and constant-phase-element pathways, connected in series through a modified constant-phase-element representing the low frequency sample-holder response. The program "ZarcFit", written in LabView, allows the operator to tune parameters of an equivalent but far more intuitive series circuit with a set of 13 sliders, and then perform a least-squares optimization. Time domain chargeability is defined by removing the effect of the sample holder, taking the Fourier transform to convert the frequency response to its time-domain equivalent and then integrating under the resulting voltage-decay curve. Time domain measurements using two-electrode sample holders are necessarily contaminated by the low-frequency response of ionic diffusion at the electrodes. Results are compiled in the Canadian Rock Physical

  15. Online Measurement of Real-Time Cytotoxic Responses Induced by Multi-Component Matrices, such as Natural Products, through Electric Cell-Substrate Impedance Sensing (ECIS).

    PubMed

    Fallarero, Adyary; Batista-González, Ana E; Hiltunen, Anna K; Liimatainen, Jaana; Karonen, Maarit; Vuorela, Pia M

    2015-11-12

    Natural products are complex matrices of compounds that are prone to interfere with the label-dependent methods that are typically used for cytotoxicity screenings. Here, we developed a label-free Electric Cell-substrate Impedance Sensing (ECIS)-based cytotoxicity assay that can be applied in the assessment of the cytotoxicity of natural extracts. The conditions to measure the impedance using ECIS were first optimized in mice immortalized hypothalamic neurons GT1-7 cells. The performance of four natural extracts when tested using three conventional cytotoxicity assays in GT1-7 cells, was studied. Betula pendula (silver birch tree) was found to interfere with all of the cytotoxicity assays in which labels were applied. The silver birch extract was also proven to be cytotoxic and, thus, served as a proof-of-concept for the use of ECIS. The extract was fractionated and the ECIS method permitted the distinction of specific kinetic patterns of cytotoxicity on the fractions as well as the extract's pure constituents. This study offers evidence that ECIS is an excellent tool for real-time monitoring of the cytotoxicity of complex extracts that are difficult to work with using conventional (label-based) assays. Altogether, it offers a very suitable cytotoxicity-screening assay making the work with natural products less challenging within the drug discovery workflow.

  16. Online Measurement of Real-Time Cytotoxic Responses Induced by Multi-Component Matrices, such as Natural Products, through Electric Cell-Substrate Impedance Sensing (ECIS)

    PubMed Central

    Fallarero, Adyary; Batista-González, Ana E.; Hiltunen, Anna K.; Liimatainen, Jaana; Karonen, Maarit; Vuorela, Pia M.

    2015-01-01

    Natural products are complex matrices of compounds that are prone to interfere with the label-dependent methods that are typically used for cytotoxicity screenings. Here, we developed a label-free Electric Cell-substrate Impedance Sensing (ECIS)-based cytotoxicity assay that can be applied in the assessment of the cytotoxicity of natural extracts. The conditions to measure the impedance using ECIS were first optimized in mice immortalized hypothalamic neurons GT1-7 cells. The performance of four natural extracts when tested using three conventional cytotoxicity assays in GT1-7 cells, was studied. Betula pendula (silver birch tree) was found to interfere with all of the cytotoxicity assays in which labels were applied. The silver birch extract was also proven to be cytotoxic and, thus, served as a proof-of-concept for the use of ECIS. The extract was fractionated and the ECIS method permitted the distinction of specific kinetic patterns of cytotoxicity on the fractions as well as the extract’s pure constituents. This study offers evidence that ECIS is an excellent tool for real-time monitoring of the cytotoxicity of complex extracts that are difficult to work with using conventional (label-based) assays. Altogether, it offers a very suitable cytotoxicity-screening assay making the work with natural products less challenging within the drug discovery workflow. PMID:26569236

  17. 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

  18. Three-dimensional electrical impedance tomography: a topology optimization approach.

    PubMed

    Mello, Luís Augusto Motta; de Lima, Cícero Ribeiro; Amato, Marcelo Britto Passos; Lima, Raul Gonzalez; Silva, Emílio Carlos Nelli

    2008-02-01

    Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.

  19. Experimental study of two-phase fluid flow in two different porosity types of sandstone by P-wave velocity and electrical Impedance measurement

    NASA Astrophysics Data System (ADS)

    Honda, H.; Mitani, Y.; Kitamura, K.; Ikemi, H.; Takaki, S.

    2015-12-01

    Carbon dioxide (CO2) capture and storage (CCS) is recently expected as the promising method to reduce greenhouse gas emissions. It is important to investigate CO2 behavior in the reservoir, to evaluate the safety and to account the stored CO2 volume. In this study, experimental investigation is conducted to discuss the relationships between injected fluid speed (Flow rate: FR) or capillary number (Ca) and non-wetting fluid flow by compressional wave velocity (Vp) and electrical impedance (Z). In the experiment, N2 and supercritical CO2 were injected into the two sandstones with different porosity (φ), Berea sandstone (φ: 18 %), and Ainoura sandstone (φ: 11.9 %). The dimension of the rock specimens is cored cylinder with a 35 mm diameter and 70 mm height. Experimental conditions are nearly same as the reservoir of deep underground (Confining pressure:15MPa, 40℃). Initial conditions of the specimen are brine (0.1wt%-KCl) saturated. Four piezo-electrical transducers (PZTs) are set on the each surface of the top, middle, lower of the specimen to monitor the CO2 bahavior by Vp. To measuring Z, we use for electrodes method with Ag-AgCl electrodes. Four electrodes are wounded around specimen on the both sides of PZTs. We measured the changes of these parameters with injecting N2, injected fluid speed (FR), the differential pore pressure (DP), N2 saturation (SN2), P-wave velocity (Vp) and electrical impedance (Z), respectively. We also estimated the Ca from measured FR. From these experimental results, there are no obvious Vp changes with increasing Ca, while Z measurement indicates clear and continuous increment. In regards to Vp, Vp reduced at the small FR (0.1 to 0.2 ml/min). As the Ca increases, Vp doesn't indicate large reduction. On the other hand, Z is more sensitive to change the fluid saturation than Vp. It is well-known that both of Vp and Z are the function of fluid saturation. Though, these experimental results are not consistent with previous studies. In

  20. The measurement of peripheral blood volume reactions to tilt test by the electrical impedance technique after exercise in athletes

    NASA Astrophysics Data System (ADS)

    Melnikov, A. A.; Popov, S. G.; Nikolaev, D. V.; Vikulov, A. D.

    2013-04-01

    We have investigated the distribution of peripheral blood volumes in different regions of the body in response to the tilt-test in endurance trained athletes after aerobic exercise. Distribution of peripheral blood volumes (ml/beat) simultaneously in six regions of the body (two legs, two hands, abdomen, neck and ECG) was assessed in response to the tilt-test using the impedance method (the impedance change rate (dZ/dT). Before and after exercise session cardiac stroke (CSV) and blood volumes in legs, arms and neck were higher in athletes both in lying and standing positions. Before exercise the increase of heart rate and the decrease of a neck blood volume in response to tilting was lower (p <0.05) but the decrease of leg blood volumes was higher (p<0.001) in athletes. The reactions in arms and abdomen blood volumes were similar. Also, the neck blood volumes as percentage of CSV (%/CSV) did not change in the control but increased in athletes (p <0.05) in response to the tilt test. After (10 min recovery) the aerobic bicycle exercise (mean HR = 156±8 beat/min, duration 30 min) blood volumes in neck and arms in response to the tilting were reduced equally, but abdomen (p<0.05) and leg blood volumes (p <0.001) were lowered more significantly in athletes. The neck blood flow (%/CSV) did not change in athletes but decreased in control (p<0.01), which was offset by higher tachycardia in response to tilt-test in controls after exercise. The data demonstrate greater orthostatic tolerance in athletes both before and after exercise during fatigue which is due to effective distribution of blood flows aimed at maintaining cerebral blood flow.

  1. Correcting electrode impedance effects in broadband SIP measurements

    NASA Astrophysics Data System (ADS)

    Huisman, Johan Alexander; Zimmermann, Egon; Esser, Odilia; Haegel, Franz-Hubert; Vereecken, Harry

    2016-04-01

    Broadband spectral induced polarization (SIP) measurements of the complex electrical resistivity can be affected by the contact impedance of the potential electrodes above 100 Hz. In this study, we present a correction procedure to remove electrode impedance effects from SIP measurements. The first step in this correction procedure is to estimate the electrode impedance using a measurement with reversed current and potential electrodes. In a second step, this estimated electrode impedance is used to correct SIP measurements based on a simplified electrical model of the SIP measurement system. We evaluated this new correction procedure using SIP measurements on water because of the well-defined dielectric properties. It was found that the difference between the corrected and expected phase of the complex electrical resistivity of water was below 0.1 mrad at 1 kHz for a wide range of electrode impedances. In addition, SIP measurements on a saturated unconsolidated sediment sample with two types of potential electrodes showed that the measured phase of the electrical resistivity was very similar (difference <0.2 mrad) up to a frequency of 10 kHz after the effect of the different electrode impedances was removed. Finally, SIP measurements on variably saturated unconsolidated sand were made. Here, the plausibility of the phase of the electrical resistivity was improved for frequencies up to 1 kHz, but errors remained for higher frequencies due to the approximate nature of the electrode impedance estimates and some remaining unknown parasitic capacitances that led to current leakage. It was concluded that the proposed correction procedure for SIP measurements improved the accuracy of the phase measurements by an order of magnitude in the kHz frequency range. Further improvement of this accuracy requires a method to accurately estimate parasitic capacitances in situ.

  2. 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.

  3. The relationship between skin maturation and electrical skin impedance.

    PubMed

    Emery, M M; Hebert, A A; Aguirre Vila-Coro, A; Prager, T C

    1991-09-01

    When performing electrophysiological testing, high electrical impedance values are sometimes found in neonates. Since excessive impedance can invalidate test results, a study was conducted to delineate the relationship between skin maturation and electrical skin impedance. This study investigated the skin impedance in 72 infants ranging from 196 to 640 days of age from conception. Regression analyses demonstrated a significant relationship between impedance and age, with the highest impedance centered around full-term gestation with values falling precipitously at time points on either side. Clinically, impedance values fall to normal levels at approximately four months following full-term gestation. Skin impedance values are low in premature infants, but rapidly increase as the age approaches that of full-term neonates. Low impedance values in premature infants are attributed to greater skin hydration which results from immature skin conditions such as 1) thinner epidermal layers particularly at the transitional and cornified layers; 2) more blood flow to the skin; and 3) higher percentage of water composition. These factors facilitate the diffusion of water vapor through the skin. As the physical barrier to skin water loss matures with gestational age, the skin impedance reaches a maximum value at full term neonatal age. After this peak, a statistically significant inverse relationship exists between electrical skin impedance and age in the first year of life. This drop in skin impedance is attributed to an increase in skin hydration as a result of the greater functional maturity of eccrine sweat glands.

  4. Voltage biasing, cyclic voltammetry, & electrical impedance spectroscopy for neural interfaces.

    PubMed

    Wilks, Seth J; Richner, Tom J; Brodnick, Sarah K; Kipke, Daryl R; Williams, Justin C; Otto, Kevin J

    2012-02-24

    Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive procedures, and can be used to monitor electrode performance over the long term. EIS measures electrical impedance at multiple frequencies, and increases in impedance indicate increased glial scar formation around the device, while cyclic voltammetry measures the charge carrying capacity of the electrode, and indicates how charge is transferred at different voltage levels. As implanted electrodes age, EIS and CV data change, and electrode sites that previously recorded spiking neurons often exhibit significantly lower efficacy for neural recording. The application of a brief voltage pulse to implanted electrode arrays, known as rejuvenation, can bring back spiking activity on otherwise silent electrode sites for a period of time. Rejuvenation alters EIS and CV, and can be monitored by these complementary methods. Typically, EIS is measured daily as an indication of the tissue response at the electrode site. If spikes are absent in a channel that previously had spikes, then CV is used to determine the charge carrying capacity of the electrode site, and rejuvenation can be applied to improve the interface efficacy. CV and EIS are then repeated to check the changes at the electrode-tissue interface, and neural recordings are collected. The overall goal of rejuvenation is to extend the functional lifetime of implanted arrays.

  5. 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.

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

    PubMed

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

    2009-12-07

    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.

  7. Single cell electric impedance topography: Mapping membrane capacitance

    PubMed Central

    Dharia, Sameera; Ayliffe, Harold E.

    2010-01-01

    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

  8. Imaging Local Electric Field Distribution by Plasmonic Impedance Microscopy.

    PubMed

    Wang, Yixian; Shan, Xiaonan; Wang, Shaopeng; Tao, Nongjian; Blanchard, Pierre-Yves; Hu, Keke; Mirkin, Michael V

    2016-02-02

    We report on imaging of local electric field on an electrode surface with plasmonic electrochemical impedance microscopy (P-EIM). The local electric field is created by putting an electrode inside a micropipet positioned over the electrode and applying a voltage between the two electrodes. We show that the distribution of the surface charge as well as the local electric field at the electrode surface can be imaged with P-EIM. The spatial distribution and the dependence of the local charge density and electric field on the distance between the micropipet and the surface are measured, and the results are compared with the finite element calculations. The work also demonstrates the possibility of integrating plasmonic imaging with scanning ion conductance microscopy (SICM) and other scanning probe microscopies.

  9. Development of electrical impedance tomography of microwave ablation

    NASA Astrophysics Data System (ADS)

    McEwan, A.; Wi, H.; Nguyen, D. T.; Jones, P.; Lam, V.; Hawthorne, W. J.; Barry, M. A.; Oh, T. I.

    2014-04-01

    In this study we assess the feasibility of electrical impedance tomography (EIT) to track the temperature changes during ablation in an ex-vivo ovine liver and in-vivo porcine model. 208 tetrapolar electrical impedance measurements were obtained at 30 frame/s from a 16 electrode EIT system. In the porcine model ventilation artefact was removed by low pass filtering and successful ablation related impedance change image sequences were reconstructed from four of nine liver ablations. This study indicates feasibility of the technique but was limited in the porcine model due to electrode difficulties and the difficulty in positioning the microwave applicator under ultrasound. EIT is more convenient and lower cost than other temperature monitoring methods such as MRI but spatial resolution is constrained by the relatively low number of independent measurements and ill posed reconstruction problem. Future improvements include the use of an internal electrode that could be in practice located on the microwave applicator to provide the reconstruction algorithm with improved prior information and local information of conductivity changes due to ablation.

  10. 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

  11. Body composition of adult cystic fibrosis patients and control subjects as determined by densitometry, bioelectrical impedance, total-body electrical conductivity, skinfold measurements, and deuterium oxide dilution

    SciTech Connect

    Newby, M.J.; Keim, N.L.; Brown, D.L. )

    1990-08-01

    This study contrasts body compositions (by six methods) of eight cystic fibrosis (CF) subjects with those of eight control subjects matched for age, height, and sex. CF subjects weighed 84% as much as control subjects. Densitometry and two bioelectrical impedance-analysis methods suggested that reduced CF weights were due to less lean tissue (10.7, 9.5, and 10.4 kg). Total-body electrical conductivity (TOBEC) and skinfold-thickness measurements indicated that CF subjects were leaner than control subjects and had less fat (5.4 and 3.6 kg) and less lean (5.2 and 7 kg) tissue. D2O dilution showed a pattern similar to TOBEC (8.3 kg less lean, 2.7 kg less fat tissue). Densitometry estimates of fat (mass and percent) were not correlated (r less than 0.74, p greater than 0.05) with any other method for CF subjects but were correlated with all other methods for control subjects. CF subjects contained less fat and lean tissue than did control subjects. Densitometry by underwater weighing is unsuitable for assessing body composition of CF patients.

  12. Structural health monitoring using piezoelectric impedance measurements.

    PubMed

    Park, Gyuhae; Inman, Daniel J

    2007-02-15

    This paper presents an overview and recent advances in impedance-based structural health monitoring. The basic principle behind this technique is to apply high-frequency structural excitations (typically greater than 30kHz) through surface-bonded piezoelectric transducers, and measure the impedance of structures by monitoring the current and voltage applied to the piezoelectric transducers. Changes in impedance indicate changes in the structure, which in turn can indicate that damage has occurred. An experimental study is presented to demonstrate how this technique can be used to detect structural damage in real time. Signal processing methods that address damage classifications and data compression issues associated with the use of the impedance methods are also summarized. Finally, a modified frequency-domain autoregressive model with exogenous inputs (ARX) is described. The frequency-domain ARX model, constructed by measured impedance data, is used to diagnose structural damage with levels of statistical confidence.

  13. Efficient Simultaneous Reconstruction of Time-Varying Images and Electrode Contact Impedances in Electrical Impedance Tomography

    PubMed Central

    Boverman, Gregory; Isaacson, David; Newell, Jonathan C.; Saulnier, Gary J.; Kao, Tzu-Jen; Amm, Bruce C.; Wang, Xin; Davenport, David M.; Chong, David H.; Sahni, Rakesh; Ashe, Jeffrey M.

    2016-01-01

    In Electrical Impedance Tomography (EIT), we apply patterns of currents on a set of electrodes at the external boundary of an object, measure the resulting potentials at the electrodes, and, given the aggregate data set, reconstruct the complex conductivity and permittivity within the object. It is possible to maximize sensitivity to internal conductivity changes by simultaneously applying currents and measuring potentials on all electrodes but this approach also maximizes sensitivity to changes in impedance at the interface. We have therefore developed algorithms to assess contact impedance changes at the interface as well as to efficiently and simultaneously reconstruct internal conductivity/permittivity changes within the body. We use simple linear algebraic manipulations, the generalized SVD, and a dual-mesh finite-element-based framework to reconstruct images in real time. We are also able to efficiently compute the linearized reconstruction for a wide range of regularization parameters and to compute both the Generalized Cross-Validation (GCV) parameter as well as the L-curve, objective approaches to determining the optimal regularization parameter, in a similarly efficient manner. Results are shown using data from a normal subject and from a clinical ICU patient, both acquired with the GE GENESIS prototype EIT system, demonstrating significantly reduced boundary artifacts due to electrode drift and motion artifact. PMID:27295649

  14. 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).

  15. Acoustic Impedance Measurement for Underground Surfaces.

    NASA Astrophysics Data System (ADS)

    Cockcroft, Paul William

    Available from UMI in association with The British Library. Requires signed TDF. This thesis investigates the measurement of acoustic impedance for surfaces likely to be found in underground coal mines. By introducing the concepts of industrial noise, the effects of noise on the ear and relevant legislation the need for the protection of workers can be appreciated. Representative acoustic impedance values are vital as input for existing computer models that predict sound levels in various underground environments. These enable the mining engineer to predict the noise level at any point within a mine in the vicinity of noisy machinery. The concepts of acoustic intensity and acoustic impedance are investigated and different acoustic impedance measurement techniques are detailed. The possible use of either an impedance tube or an intensity meter for these kinds of measurements are suggested. The problems with acoustic intensity and acoustic impedance measurements are discussed with reference to the restraints that an underground environment imposes on any measurement technique. The impedance tube method for work in an acoustics laboratory is shown and the theory explained, accompanied by a few representative results. The use of a Metravib intensity meter in a soundproof chamber to gain impedance values is explained in detail. The accompanying software for the analysis of the two measured pressure signals is shown as well as the actual results for a variety of test surfaces. The use of a Nagra IV-SJ tape recorder is investigated to determine the effect of recording on the measurement and subsequent analysis of the input signals, particularly with reference to the phase difference introduced between the two simultaneous pressure signals. The subsequent use of a Norwegian Electronic intensity meter, including a proposal for underground work, is shown along with results for tests completed with this piece of equipment. Finally, recommendations are made on how to link up

  16. Hyperaemia evaluation in clinical diathermy by four-electrode impedance measurements.

    PubMed

    Olmi, R; Bini, M; Ignesti, A; Feroldi, P; Spiazzi, L; Bodini, G

    1997-01-01

    The four-electrode electrical impedance measurement technique is proposed for the evaluation of the hyperaemia variation in tissues treated by diathermic therapy. An impedance meter suitable for such measurements is described, and an electrical model of the heated tissues, concerning the impedance variation during diathermy and its relation with hyperaemia, is presented. The occurrence of the substantial contribution of blood to the overall transverse impedance is demonstrated by comparing the experimental results with those arising from a 2D electrical/thermal model of the treated tissues. A two-admittance model is proposed to explain the electrical behaviour of the tissues treated by diathermy. The model allows us to separate the impedance violation due to the temperature dependence of tissue conductivity from that due to the change of tissue blood content. The results of preliminary measurements of tissue impedance on healthy volunteers treated by electromagnetic diathermy are presented and discussed, showing the feasibility of impedance detection of hyperaemia variations inside tissues.

  17. Electrical impedance characterization of cell growth on interdigitated microelectrode array.

    PubMed

    Lee, Gi Hyun; Pyun, Jae-Chul; Cho, Sungbo

    2014-11-01

    Electrical cell-substrate impedance sensing is a method for label-free and real-time monitoring of biological cells, which has been increasingly employed in the diagnostic and pharmaceutical industries. In this study, we fabricated an interdigitated electrode (IDE) array, which consists of 10 fingers, with a length of 1.2 mm, width of 50 μm, spacing of 50 μm, and thickness of 75 nm. The impedance spectra of the fabricated IDE were measured without or with cells in the frequency range of 100 Hz to 100 kHz using a lock-in amplifier based system and characterized by equivalent circuit modelling. Regarding the total impedance as a series resistance (R) and capacitance (C) model, R and C parameters were traced at a selected frequency during cell growth. It was able to monitor cell adherence and proliferation dependent on the behaviours and characteristics of cells on the fabricated IDE array by monitoring RC parameters. The degree of changes in RC value during cell growth was dependent on the type of cells used.

  18. Modeling the electric image produced by objects with complex impedance in weakly electric fish.

    PubMed

    Fujita, Kazuhisa; Kashimori, Yoshiki

    2010-08-01

    Weakly electric fish generate an electric field around their body by electric organ discharge (EOD). By measuring the modulation of the electric field produced by an object in the field these fish are able to accurately locate an object. Theoretical and experimental studies have focused on the amplitude modulations of EODs produced by resistive objects. However, little is known about the phase modulations produced by objects with complex impedance. The fish must be able to detect changes in object impedance to discriminate between food and nonfood objects. To investigate the features of electric images produced by objects with complex impedance, we developed a model that can be used to map the electric field around the fish body. The present model allows us to calculate the spatial distribution of the amplitude and phase shift in an electric image. This is the first study to investigate the changes in amplitude and phase shift of electric images induced by objects with complex impedance in wave-type fish. Using the model, we show that the amplitude of the electric image exhibits a sigmoidal change as the capacitance and resistance of an object are increased. Similarly, the phase shift exhibits a significant change within the object capacitance range of 0.1-100 nF. We also show that the spatial distribution of the amplitude and phase shifts of the electric image resembles a "Mexican hat" in shape for varying object distances and sizes. The spatial distribution of the phase shift and the amplitude was dependent on the object distance and size. Changes in the skin capacitance were associated with a tradeoff relationship between the magnitude of the amplitude and phase shift of the electric image. The specific range of skin capacitance (1-100 nF) allows the receptor afferents to extract object features that are relevant to electrolocation. These results provide a useful basis for the study of the neural mechanisms by which weakly electric fish recognize object features

  19. Studies of an Adaptive Kaczmarz Method for Electrical Impedance Imaging

    NASA Astrophysics Data System (ADS)

    Li, Taoran; Isaacson, David; Newell, Jonathan C.; Saulnier, Gary J.

    2013-04-01

    We present an adaptive Kaczmarz method for solving the inverse problem in electrical impedance tomography and determining the conductivity distribution inside an object from electrical measurements made on the surface. To best characterize an unknown conductivity distribution and avoid inverting the Jacobian-related term JTJ which could be expensive in terms of memory storage in large scale problems, we propose to solve the inverse problem by adaptively updating both the optimal current pattern with improved distinguishability and the conductivity estimate at each iteration. With a novel subset scheme, the memory-efficient reconstruction algorithm which appropriately combines the optimal current pattern generation and the Kaczmarz method can produce accurate and stable solutions adaptively compared to traditional Kaczmarz and Gauss-Newton type methods. Several reconstruction image metrics are used to quantitatively evaluate the performance of the simulation results.

  20. Adaptive Kaczmarz Method for Image Reconstruction in Electrical Impedance Tomography

    PubMed Central

    Li, Taoran; Kao, Tzu-Jen; Isaacson, David; Newell, Jonathan C.; Saulnier, Gary J.

    2013-01-01

    We present an adaptive Kaczmarz method for solving the inverse problem in electrical impedance tomography and determining the conductivity distribution inside an object from electrical measurements made on the surface. To best characterize an unknown conductivity distribution and avoid inverting the Jacobian-related term JTJ which could be expensive in terms of computation cost and memory in large scale problems, we propose solving the inverse problem by applying the optimal current patterns for distinguishing the actual conductivity from the conductivity estimate between each iteration of the block Kaczmarz algorithm. With a novel subset scheme, the memory-efficient reconstruction algorithm which appropriately combines the optimal current pattern generation with the Kaczmarz method can produce more accurate and stable solutions adaptively as compared to traditional Kaczmarz and Gauss-Newton type methods. Choices of initial current pattern estimates are discussed in the paper. Several reconstruction image metrics are used to quantitatively evaluate the performance of the simulation results. PMID:23718952

  1. Impedance spectral measurements made through a membrane infection barrier.

    PubMed

    Brown, Brian H; Gonzalez-Correa, Carlos A; Bremner, John; Tidy, John A

    2006-12-01

    Impedance spectra of superficial tissues can be used to detect pre-malignant changes in the cervix but require electrical contact to be made between a probe and the tissue. Using a membrane which is permeable to ions but forms a barrier to agents of infection should enable impedance spectra to be measured without causing an infection risk to the patient. The properties required of such a membrane are considered and measurements on two suitable membranes are presented. It is shown that impedance spectra can be measured through a thin natural cellulose based membrane (Cuprophan) and that these are not significantly different from directly measured spectra. The ability of the membranes to block a virus is tested using expired polio virus vaccine.

  2. The influence of urine volume on body impedance measurement.

    PubMed

    Hong, K H; Park, K S

    2008-01-01

    Bio-signal has some characteristics that the signal is so weak. So, it is good that the factors to influence measured electrical signal are eliminated as much as they can. So, in this paper we will show the influence of urine in bladder on measuring human body impedance. Human urine has different conductivity from other human tissues. Therefore, if the volume of the urine changed, the measured body impedance data also changed.So, in this paper, we will show the influence of urine in bladder with foot-to-foot and thigh-to-thigh current paths. As a result, if the current flows through human bladder, the influence of urine in the bladder must be considered when the body impedance is measured

  3. 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.

  4. 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

  5. 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.

  6. Possibilities for predictive measurement of the transthoracic impedance in defibrillation.

    PubMed

    Krasteva, V; Hatib, F A; Trendafilova, E; Daskalov, I

    2001-01-01

    Transthoracic electrical defibrillation is administered by high voltages and currents applied through large size electrodes. Therefore, the defibrillator load impedance becomes an essential factorfor the efficacy of the procedure. Attempts at prediction of transthoracic impedance by pre-shock measurement with low-amplitude high-frequency current have yielded apparently promising results. A reassessment was undertaken of the comparison between transthoracic impedance measured over a wide frequency range (bioimpedance spectroscopy) and measured during the shock. An estimation of the possibilities for pre-shock 'prediction ' of the impedance was performed, to allow adequate selection of the defibrillation energy or current with the intention of increasing the possibility for positive results with the first shock. Data were obtained from experimental fibrillation/defibrillation cycles on dogs andfrom cardioversion of atrial fibrillation or flutter in patients. The final results suggest that high-frequency low-amplitude impedance measurements cannot predict the corresponding value during the shock with very high accuracy, as differences up to 15-17% were found using biphasic pulses in patients. However, the method can be used for approximate assessments.

  7. 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.

  8. Handheld Electrical Impedance Myography Probe for Assessing Carpal Tunnel Syndrome.

    PubMed

    Li, Zhao; Chen, Lingfen; Zhu, Yu; Wei, Qingquan; Liu, Wenwen; Tian, Dong; Yu, Yude

    2017-03-30

    Electrical impedance myography (EIM) is a novel, noninvasive, and painless technique for quantitatively assessing muscle health as well as disease status and progression. The preparatory work for commercial adhesive electrodes used in previous EIM measurements is tedious, as the electrodes need to be cut, repeatedly applied, and removed. Moreover, the electrode distances need to be measured many times. To overcome these problems, we developed a convenient and practical handheld EIM probe for assessing carpal tunnel syndrome (CTS) in the small hand muscles. To reduce the electrode-skin contact impedance (ESCI), the micropillared and microholed stainless steel electrodes (SSEs) contained in the probe were fabricated using a laser processing technique. When covered with saline, these electrodes showed lower ESCIs than a smooth SSE and Ag/AgCl electrode. The probe was shown to have excellent test-retest reproducibility in both healthy subjects and CTS patients, with intraclass correlation coefficients exceeding 0.975. The reactance and phase values of the abductor pollicis brevis (affected muscle) for CTS patients were consistently lower than those for healthy subjects, with a 50-kHz difference of 37.1% (p < 0.001) and 31.0% (p < 0.001), respectively. Further, no significant differences were detected in the case of the abductor digiti minimi (unaffected muscle). These results indicate that EIM has considerable potential for CTS assessment and hence merits further investigation.

  9. Sensorless battery temperature measurements based on electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Raijmakers, L. H. J.; Danilov, D. L.; van Lammeren, J. P. M.; Lammers, M. J. G.; Notten, P. H. L.

    2014-02-01

    A new method is proposed to measure the internal temperature of (Li-ion) batteries. Based on electrochemical impedance spectroscopy measurements, an intercept frequency (f0) can be determined which is exclusively related to the internal battery temperature. The intercept frequency is defined as the frequency at which the imaginary part of the impedance is zero (Zim = 0), i.e. where the phase shift between the battery current and voltage is absent. The advantage of the proposed method is twofold: (i) no hardware temperature sensors are required anymore to monitor the battery temperature and (ii) the method does not suffer from heat transfer delays. Mathematical analysis of the equivalent electrical-circuit, representing the battery performance, confirms that the intercept frequency decreases with rising temperatures. Impedance measurements on rechargeable Li-ion cells of various chemistries were conducted to verify the proposed method. These experiments reveal that the intercept frequency is clearly dependent on the temperature and does not depend on State-of-Charge (SoC) and aging. These impedance-based sensorless temperature measurements are therefore simple and convenient for application in a wide range of stationary, mobile and high-power devices, such as hybrid- and full electric vehicles.

  10. Plasma Impedance Spectrum Analyzer (PISA): an advanced impedance probe for measuring plasma density and other parameters

    NASA Astrophysics Data System (ADS)

    Rowland, D. E.; Pfaff, R. F.; Uribe, P.; Burchill, J.

    2006-12-01

    as close as possible to the plasma potential, collapsing the ion sheath and minimizing sheath-induced errors in the measurement of the temperature-dependent series resonance frequency. In addition, by stepping the bias voltage through a range of values, we can measure the sheath capacitance as a function of voltage and get an independent measure of the Debye length. 3) Drive voltage amplitude stepping which allows the diagnosis of sheath rectification and non-linear effects that may drive harmonics of the plasma / upper hybrid frequency. By stepping the amplitude through a range, we can also find the optimal drive voltage which provides a reasonable SNR while minimizing the impedance probe's impact on other instruments, such as high frequency electric field probes. We present flight data from representative souding rocket flights of the Goddard Impedance Probe and discuss the instrument performance, error bars, and future improvements.

  11. [Image reconstruction in electrical impedance tomography based on genetic algorithm].

    PubMed

    Hou, Weidong; Mo, Yulong

    2003-03-01

    Image reconstruction in electrical impedance tomography (EIT) is a highly ill-posed, non-linear inverse problem. The modified Newton-Raphson (MNR) iteration algorithm is deduced from the strictest theoretic analysis. It is an optimization algorithm based on minimizing the object function. The MNR algorithm with regularization technique is usually not stable, due to the serious image reconstruction model error and measurement noise. So the reconstruction precision is not high when used in static EIT. A new static image reconstruction method for EIT based on genetic algorithm (GA-EIT) is proposed in this paper. The experimental results indicate that the performance (including stability, the precision and space resolution in reconstructing the static EIT image) of the GA-EIT algorithm is better than that of the MNR algorithm.

  12. 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.

  13. Electric impedance method for evaluation of the release property of calcein-encapsulated liposomes.

    PubMed

    Chen, Guoming; Jiang, Zhongwei; Yoshimoto, Makoto; Wei, Yunlong

    2009-11-01

    This paper is concerned with the study on development of a novel method for evaluation of the liposomes release property by measuring the electric impedance changes of liposome suspensions. Calcein/NaOH encapsulated liposomes (calcein-liposomes) were prepared with deionized water and were treated with ultrasonic irradiation in order to investigate the release property of the liposomes. To validate the proposed impedance measuring method, the calcein release rates were evaluated both by the impedance changes and the fluorescence intensity changes in calcein-liposome suspensions. With the comparison of these results obtained by the two methods, it is shown that the impedance method has much wider detecting concentration range than the fluorescence one. Furthermore, the impedance method can be efficiently used for evaluation of the release property on various ionic substances encapsulated within liposomes.

  14. 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

  15. 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.

  16. [Electrical impedance tomography: standardizing the procedure in pneumology].

    PubMed

    de Lema, Bruno; Casan, Pere; Riu, Pere

    2006-06-01

    The following conditions are optimal for obtaining an adequate number of informative images by electric impedance tomography: a) patient seated or standing with hands at the nape of the neck; b) breathing at rest; c) recording of at least 300 images (at a frequency of 10 Hz), and d) readings taken at the sixth intercostal space.

  17. Using independent component analysis for electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Yan, Peimin; Mo, Yulong

    2004-05-01

    Independent component analysis (ICA) is a way to resolve signals into independent components based on the statistical characteristics of the signals. It is a method for factoring probability densities of measured signals into a set of densities that are as statistically independent as possible under the assumptions of a linear model. Electrical impedance tomography (EIT) is used to detect variations of the electric conductivity of the human body. Because there are variations of the conductivity distributions inside the body, EIT presents multi-channel data. In order to get all information contained in different location of tissue it is necessary to image the individual conductivity distribution. In this paper we consider to apply ICA to EIT on the signal subspace (individual conductivity distribution). Using ICA the signal subspace will then be decomposed into statistically independent components. The individual conductivity distribution can be reconstructed by the sensitivity theorem in this paper. Compute simulations show that the full information contained in the multi-conductivity distribution will be obtained by this method.

  18. Electric impedance microflow cytometry for characterization of cell disease states.

    PubMed

    Du, E; Ha, Sungjae; Diez-Silva, Monica; Dao, Ming; Suresh, Subra; Chandrakasan, Anantha P

    2013-10-07

    The electrical properties of biological cells have connections to their pathological states. Here we present an electric impedance microflow cytometry (EIMC) platform for the characterization of disease states of single cells. This platform entails a microfluidic device for a label-free and non-invasive cell-counting assay through electric impedance sensing. We identified a dimensionless offset parameter δ obtained as a linear combination of a normalized phase shift and a normalized magnitude shift in electric impedance to differentiate cells on the basis of their pathological states. This paper discusses a representative case study on red blood cells (RBCs) invaded by the malaria parasite Plasmodium falciparum. Invasion by P. falciparum induces physical and biochemical changes on the host cells throughout a 48-h multi-stage life cycle within the RBC. As a consequence, it also induces progressive changes in electrical properties of the host cells. We demonstrate that the EIMC system in combination with data analysis involving the new offset parameter allows differentiation of P. falciparum infected RBCs from uninfected RBCs as well as among different P. falciparum intraerythrocytic asexual stages including the ring stage. The representative results provided here also point to the potential of the proposed experimental and analysis platform as a valuable tool for non-invasive diagnostics of a wide variety of disease states and for cell separation.

  19. Electric Impedance Microflow Cytometry for Characterization of Cell Disease States†

    PubMed Central

    Diez-Silva, Monica; Dao, Ming; Suresh, Subra; Chandrakasan, Anantha P.

    2013-01-01

    The electrical properties of biological cells have connections to their pathological states. Here we present an electric impedance microflow cytometry (EIMC) platform for the characterization of disease states of single cells. This platform entails a microfluidic device for a label-free and non-invasive cell-counting assay through electric impedance sensing. We identified a dimensionless offset parameter δ obtained as a linear combination of a normalized phase shift and a normalized magnitude shift in electric impedance to differentiate cells on the basis of their pathological states. This paper discusses a representative case study on red blood cells (RBCs) invaded by Plasmodium falciparum malaria parasites. Invasion of P. falciparum induces physical and biochemical changes on the host cells throughout a 48-h multi-stage life cycle within the RBC. As a consequence, it also induces progressive changes in electrical properties of the host cells .We demonstrate that the EIMC system in combination with data analysis involving the new offset parameter allows differentiation of Pf–invaded RBCs from uninfected RBCs as well as among different P. falciparum intraerythrocytic asexual stages including the ring stage. The representative results provided here also point to the potential of the proposed experimental and analysis platform as a valuable tool for non-invasive diagnostics of a wide variety of disease states and for cell separation. PMID:23925122

  20. The gastric emptying of food as measured by gamma-scintigraphy and electrical impedance tomography (EIT) and its influence on the gastric emptying of tablets of different dimensions.

    PubMed

    Podczeck, Fridrun; Mitchell, Catherine L; Newton, J Michael; Evans, David; Short, Michael B

    2007-11-01

    A study in human volunteers has been designed to evaluate the influence of different food regimes on the gastric emptying of 3 mm and 10 mm diameter tablets. Dextrose and beef drinks were used as liquid food; a mixture of minced beef and mashed potato (shepherd's pie) was used as a solid meal. The gastric emptying of these foods was monitored simultaneously with electrical impedance tomography (EIT) and gamma-scintigraphy (GS), and was quantified in terms of the time before gastric emptying started, the lag time, the mean gastric residence time (MGRT) and its variance (VGRT), and the time for complete emptying. The gastric emptying time of the tablets was established by monitoring the position of the tablets, which had been labelled with suitable radio isotopes, by GS. The two systems for monitoring gastric emptying of the foods did not provide equivalent results: times obtained with EIT were generally shorter than those obtained with GS for the liquid foods, but were longer for the solid meal. There was only a slight difference in the emptying times of the two liquid foods, whereas values for MGRT, VGRT and the time for complete emptying were considerably longer for the solid meal. In nearly all instances the tablets emptied after the foods had emptied completely from the stomach. Gastric emptying times were longer for the 3 mm tablets than the 10 mm tablets, whatever food they were taken with. The difference between the median emptying times was significant when the meal was either a dextrose solution or a beef drink, but not when the meal was shepherd's pie. The increase in gastric emptying time of tablets induced by solid food was greater than that associated with the differences in tablet size. By providing a protocol that did not allow the administration of further food until after the tablets had emptied from the stomach, no tablet emptying times exceeded 6 h.

  1. 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.

  2. Probe impedance measurements for millimeter-wave integrated horn antennas

    NASA Technical Reports Server (NTRS)

    Guo, Yong; Chiao, Jung-Chih; Potter, Kent A.; Rutledge, David B.

    1993-01-01

    In order to achieve an impedance-matched millimeter-wave integrated horn antenna mixer array, the characteristics of the antenna probes inside the horn must be known. This paper describes impedance measurements for various probes in low-frequency model horns of two different types: (1) a 3 x 3 array made of aluminum by electric discharge machining and (2) a half horn made of copper sheet placed on a big copper-clad circuit board that was used as an image plane. The results of measurements indicate that the presence of the horn increases the effective length of the probe element, in agreement with reports of Guo et al. (1991) and theoretical analysis of Eleftheriades et al. (1991). It was also found that the resonant frequencies can be controlled by changing the length of the probes or by loading the probes.

  3. Algorithmic Error Correction of Impedance Measuring Sensors

    PubMed Central

    Starostenko, Oleg; Alarcon-Aquino, Vicente; Hernandez, Wilmar; Sergiyenko, Oleg; Tyrsa, Vira

    2009-01-01

    This paper describes novel design concepts and some advanced techniques proposed for increasing the accuracy of low cost impedance measuring devices without reduction of operational speed. The proposed structural method for algorithmic error correction and iterating correction method provide linearization of transfer functions of the measuring sensor and signal conditioning converter, which contribute the principal additive and relative measurement errors. Some measuring systems have been implemented in order to estimate in practice the performance of the proposed methods. Particularly, a measuring system for analysis of C-V, G-V characteristics has been designed and constructed. It has been tested during technological process control of charge-coupled device CCD manufacturing. The obtained results are discussed in order to define a reasonable range of applied methods, their utility, and performance. PMID:22303177

  4. The electrical properties of Titan's surface at the Huygens landing site measured with the PWA-HASI Mutual Impedance Probe. New approach and new findings

    NASA Astrophysics Data System (ADS)

    Hamelin, Michel; Lethuillier, Anthony; Le Gall, Alice; Grard, Réjean; Béghin, Christian; Schwingenschuh, Konrad; Jernej, Irmgard; López-Moreno, José-Juan; Brown, Vic; Lorenz, Ralph D.; Ferri, Francesca; Ciarletti, Valérie

    2016-05-01

    Ten years after the successful landing of the Huygens Probe on the surface of Titan, we reassess the derivation of ground complex permittivity using the PWA-MIP/HASI measurements (Permittivity, Waves and Altimetry-Mutual Impedance Probe/Huygens Atmospheric Structure Instrument) at the frequencies 45, 90 and 360 Hz. For this purpose, we have developed a numerical method, namely "the capacity-influence matrix method", able to account for new insights on the Huygens Probe attitude at its final resting position. We find that the surface of Titan at the landing site has a dielectric constant of 2.5 ± 0.3 and a conductivity of 1.2 ± 0.6 nS/m, in agreement with previously published results but with much more reliable error estimates. These values speak in favour of a photochemical origin of the material in the first meter of the subsurface. We also propose, for the first time, a plausible explanation for the sudden change observed by PWA-MIP ∼11 min after landing: this change corresponds to a drop in the ground conductivity, probably due to the removal of a superficial conductive layer in association with the release of volatile materials warmed by the Huygens Probe.

  5. 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.

  6. Measurement of the Impedance of Frog Skeletal Muscle Fibers

    PubMed Central

    Valdiosera, R.; Clausen, C.; Eisenberg, R. S.

    1974-01-01

    Impedance measurements are necessary to determine the passive electrical properties of cells including the equivalent circuits of the several pathways for current flow. Such measurements are usually made with microelectrodes of high impedance (some 15 MΩ) over a wide frequency range (1-10,000 Hz) and so are subject to many errors. An input amplifier has been developed which has negligible phase shift in this frequency range because it uses negative feedback to keep tiny the voltage on top of the microelectrode. An important source of artifact is the extracellular potential produced by capacitive current flow through the wall of the microelectrodes and the effective resistance of the bathing solution. This artifact is reduced some 10 times by shielding the current microelectrode with a conductive paint. The residual artifact is analyzed, measured, and subtracted from our results. The interelectrode coupling capacitance is reduced below 2 × 10-17 F and can be neglected. Phase and amplitude measurements are made with phase-sensitive detectors insensitive to noise. The entire apparatus is calibrated at different signal to noise ratios and the nature of the extracellular potential is investigated. The phase shift in the last 5-20 μm of the microelectrode tip is shown to be small and quite independent of frequency under several conditions. Experimental measurements of the phase characteristic of muscle fibers in normal Ringer are presented. The improvements in apparatus and the physiological significance of impedance measurements are discussed. It is suggested that the interpretation of impedance measurements is sensitive to small errors and so it is necessary to present objective evidence of the reliability of one's apparatus and measurements. PMID:4857358

  7. Noninvasive measurement of transdermal drug delivery by impedance spectroscopy

    PubMed Central

    Arpaia, Pasquale; Cesaro, Umberto; Moccaldi, Nicola

    2017-01-01

    The effectiveness in transdermal delivery of skin permeation strategies (e.g., chemical enhancers, vesicular carrier systems, sonophoresis, iontophoresis, and electroporation) is poorly investigated outside of laboratory. In therapeutic application, the lack of recognized techniques for measuring the actually-released drug affects the scientific concept itself of dosage for topically- and transdermally-delivered drugs. Here we prove the suitability of impedance measurement for assessing the amount of drug penetrated into the skin after transdermal delivery. In particular, the measured amount of drug depends linearly on the impedance magnitude variation normalized to the pre-treated value. Three experimental campaigns, based on the electrical analysis of the biological tissue behavior due to the drug delivery, are reported: (i) laboratory emulation on eggplants, (ii) ex-vivo tests on pig ears, and finally (iii) in-vivo tests on human volunteers. Results point out that the amount of delivered drug can be assessed by reasonable metrological performance through a unique measurement of the impedance magnitude at one single frequency. In particular, in-vivo results point out sensitivity of 23 ml−1, repeatability of 0.3%, non-linearity of 3.3%, and accuracy of 5.7%. Finally, the measurement resolution of 0.20 ml is compatible with clinical administration standards. PMID:28338008

  8. A 4-compartment model based validation of air displacement plethysmography, dual energy X-ray absorptiometry, skinfold technique & bio-electrical impedance for measuring body fat in Indian adults

    PubMed Central

    Kuriyan, Rebecca; Thomas, Tinku; Ashok, Sangeetha; J, Jayakumar; Kurpad, Anura V.

    2014-01-01

    Background & objectives: Many methods are available for measuring body fat of an individual, each having its own advantages and limitations. The primary objective of the present study was to validate body fat estimates from individual methods using the 4-compartment (4C) model as reference. The second objective was to obtain estimates of hydration of fat free mass (FFM) using the 4C model. Methods: The body fat of 39 adults (19 men and 20 women) aged 20-40 yr was estimated using air displacement plethysmography (ADP), dual energy X-ray absorptiometry (DEXA), 4-skinfold technique and bio-electrical impedance (BIA). Total body water was estimated using isotope dilution method. Results: All the methods underestimated body fat when compared to 4C model, except for DEXA and the mean difference from the reference was lowest for DEXA and ADP. The precision of the fat mass estimated from 4C model using the propagation of error was 0.25 kg, while the mean hydration factor obtained by the 4C model was found to be 0.74 ± 0.02 in the whole group of men and women. Interpretations & conclusion: The results of the present study suggest that DEXA and ADP methods can provide reasonably accurate estimates of body fat, while skinfold and bio-electrical impedance methods require the use of population specific equations. PMID:25027079

  9. Nuclear radiation-warning detector that measures impedance

    DOEpatents

    Savignac, Noel Felix; Gomez, Leo S; Yelton, William Graham; Robinson, Alex; Limmer, Steven

    2013-06-04

    This invention is a nuclear radiation-warning detector that measures impedance of silver-silver halide on an interdigitated electrode to detect light or radiation comprised of alpha particles, beta particles, gamma rays, X rays, and/or neutrons. The detector is comprised of an interdigitated electrode covered by a layer of silver halide. After exposure to alpha particles, beta particles, X rays, gamma rays, neutron radiation, or light, the silver halide is reduced to silver in the presence of a reducing solution. The change from the high electrical resistance (impedance) of silver halide to the low resistance of silver provides the radiation warning that detected radiation levels exceed a predetermined radiation dose threshold.

  10. In vivo intravascular electric impedance spectroscopy using a new catheter with integrated microelectrodes.

    PubMed

    Süselbeck, Tim; Thielecke, Hagen; Weinschenk, Ines; Reininger-Mack, Alexandra; Stieglitz, Thomas; Metz, Jürgen; Borggrefe, Martin; Robitzki, Andrea; Haase, Karl K

    2005-01-01

    Interventional techniques are necessary, which allow the characterization of intravascular pathological processes. Electric impedance spectroscopy (EIS) can provide cellular information of biological tissue. We tested the feasibility of intravascular EIS by using a new impedance catheter system with integrated microelectrodes in an experimental animal model. Eighteen stents were implanted into the iliac arteries of female New Zealand White rabbits (n = 11) to induce intimal proliferation. After 14, 28 and 56 days the electric impedance was measured inside and outside of the stented arterial segments by using a balloon catheter with four integrated microelectrodes. The impedance was recorded at a frequency ranging from 1 Hz to 1 MHz. After the measurements, the stents were explanted and histomorphometry was performed. The impedance inside and outside the stent was analysed and compared with the histomorphometric data. Fourteen (n = 6), 28 (n = 5) and 56 (n = 6) days after stent implantation the difference of the electrical impedance between the native and the stented iliac artery segment increased from -924 +/- 715 Ohm to 3689 +/- 1385 Ohm (14 days vs. 28 days; p < 0.05) and 8637 +/- 2881 Ohm (14 days vs. 56 days; p < 0.05), respectively. The increase of the electrical impedance corresponded to an increased neointimal proliferation in the stented arterial segment of 3.6% +/-0.7% after 14 days, 8.4% +/- 4.8% after 28 days (14 days vs. 28 days; p < 0.05) and 10.0% +/- 4.1% after 56 days (14 days vs. 56 days; p < 0.01). Intravascular EIS can be performed by a balloon catheter with integrated microelectrodes and allows the detection of neointimal proliferation after stent implantation.

  11. Novel method to determine instantaneous blood volume in pulsatile blood pump using electrical impedance.

    PubMed

    Sasaki, E; Nakatani, T; Taenaka, Y; Takano, H; Hirose, H

    1994-08-01

    A novel real-time volumetric method was developed for a pulsatile pump. This method, the impedance method, used electrical impedance change in the blood chamber according to volume change while pumping. This method was evaluated with two kinds of air-driven diaphragm pumps. During in vitro tests, the impedance method indicated real-time volume change, and there was excellent correlation between computed stroke volume with the impedance method and measured stroke volume with the electromagnetic flowmeter. In chronic animal tests with goats and in a clinical case, the impedance method measured pump output accurately, and it detected diaphragm motion in real-time. In addition, excellent durability was seen. Full-fill to full-empty drive was realized accurately with this method. Application of the impedance method was easy, and it did not deteriorate native antithrombogencity of the pump. The impedance method is practical and useful to estimate the pumping condition of a pulsatile blood pump, especially a diaphragm pump. This method would be useful in clinical application.

  12. Parallel hybrid algorithm for solution in electrical impedance equation

    NASA Astrophysics Data System (ADS)

    Ponomaryov, Volodymyr; Robles-Gonzalez, Marco; Bucio-Ramirez, Ariana; Ramirez-Tachiquin, Marco; Ramos-Diaz, Eduardo

    2015-02-01

    This work is dedicated to the analysis of the forward and the inverse problem to obtain a better approximation to the Electrical Impedance Tomography equation. In this case, we employ for the forward problem the numerical method based on the Taylor series in formal power and for the inverse problem the Finite Element Method. For the analysis of the forward problem, we proposed a novel algorithm, which employs a regularization technique for the stability, additionally the parallel computing is used to obtain the solution faster; this modification permits to obtain an efficient solution of the forward problem. Then, the found solution is used in the inverse problem for the approximation employing the Finite Element Method. The algorithms employed in this work are developed in structural programming paradigm in C++, including parallel processing; the time run analysis is performed only in the forward problem because the Finite Element Method due to their high recursive does not accept parallelism. Some examples are performed for this analysis, in which several conductivity functions are employed for two different cases: for the analytical cases: the exponential and sinusoidal functions are used, and for the geometrical cases the circle at center and five disk structure are revised as conductivity functions. The Lebesgue measure is used as metric for error estimation in the forward problem, meanwhile, in the inverse problem PSNR, SSIM, MSE criteria are applied, to determine the convergence of both methods.

  13. Bioelectrical impedance analysis. What does it measure?

    NASA Technical Reports Server (NTRS)

    Schoeller, D. A.

    2000-01-01

    Bioelectrical impedance analysis (BIA) has been proposed for measuring fat-free mass, total body water, percent fat, body cell mass, intracellular water, and extracellular water: a veritable laboratory in a box. Although it is unlikely that BIA is quite this versatile, correlations have been demonstrated between BIA and all of these body compartments. At the same time, it is known that all of the compartments are correlated among themselves. Because of this, it is difficult to determine whether BIA is specific for any or all of these compartments. To investigate this question, we induced acute changes in total body water and its compartments over a 3-h period. Using this approach, we demonstrated that multifrequency BIA, using the Cole-Cole model to calculate the zero frequency and infinite frequency resistance, measures extracellular and intracellular water.

  14. All electronic approach for high-throughput cell trapping and lysis with electrical impedance monitoring.

    PubMed

    Ameri, Shideh Kabiri; Singh, Pramod K; Dokmeci, Mehmet R; Khademhosseini, Ali; Xu, Qiaobing; Sonkusale, Sameer R

    2014-04-15

    We present a portable lab-on-chip device for high-throughput trapping and lysis of single cells with in-situ impedance monitoring in an all-electronic approach. The lab-on-chip device consists of microwell arrays between transparent conducting electrodes within a microfluidic channel to deliver and extract cells using alternating current (AC) dielectrophoresis. Cells are lysed with high efficiency using direct current (DC) electric fields between the electrodes. Results are presented for trapping and lysis of human red blood cells. Impedance spectroscopy is used to estimate the percentage of filled wells with cells and to monitor lysis. The results show impedance between electrodes decreases with increase in the percentage of filled wells with cells and drops to a minimum after lysis. Impedance monitoring provides a reasonably accurate measurement of cell trapping and lysis. Utilizing an all-electronic approach eliminates the need for bulky optical components and cameras for monitoring.

  15. 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.

  16. Electric impedance tomography for monitoring volume and size of the urinary bladder.

    PubMed

    Leonhardt, Steffen; Cordes, Axel; Plewa, Harry; Pikkemaat, Robert; Soljanik, Irina; Moehring, Klaus; Gerner, Hans J; Rupp, Rüdiger

    2011-12-01

    A novel non-invasive technique for monitoring fluid content in the human bladder is described. Specifically, a precommercial electric impedance tomograph (EIT) was applied to measure and visualize impedance changes in the lower torso due to changes in bladder volume. Preliminary measurements were conducted during routine urodynamic tests of nine male paraplegic patients, in whom a contrast agent was slowly infused into the bladder for diagnostic purposes. In some patients, a good correlation between bladder volume and EIT measurements was found, whereas in others the correlation was still good but inverted, presumably due to a poor electrode positioning. These preliminary results indicate that a sufficiently accurate finite element modeling of the impedance distribution in the abdomen, and proper electrode positioning aids, are important prerequisites to enable this technology to be used for routine measurement of bladder volume.

  17. Evaluation of a novel correction procedure to remove electrode impedance effects from broadband SIP measurements

    NASA Astrophysics Data System (ADS)

    Huisman, Johan Alexander; Zimmermann, Egon; Esser, Odilia; Haegel, Franz-Hubert; Treichel, Andrea; Vereecken, Harry

    2016-12-01

    Broadband spectral induced polarization (SIP) measurements of the complex electrical resistivity can be affected by the contact impedance of the potential electrodes above 100 Hz. In this study, we present a correction procedure to remove electrode impedance effects from SIP measurements to improve the accuracy of broadband complex electrical resistivity measurements. The first step in this correction procedure is to estimate the electrode impedance using a measurement with reversed current and potential electrodes. In a second step, this estimated electrode impedance is used to correct SIP measurements based on a simplified electrical model of the SIP measurement system. We evaluated this new correction procedure using SIP measurements on water because of the well-defined dielectric properties. It was found that the difference between the corrected and expected phase of the complex electrical resistivity of water was below 0.1 mrad at 1 kHz for a wide range of electrode impedances. In addition, SIP measurements on a saturated unconsolidated sediment sample with two types of potential electrodes showed that the measured phase of the electrical resistivity was very similar (difference < 0.2 mrad) up to a frequency of 10 kHz after the effect of the different electrode impedances was removed. Finally, SIP measurements on variably saturated unconsolidated sand were made. Here, the plausibility of the phase of the electrical resistivity was improved for frequencies up to 1 kHz, but errors remained for higher frequencies due to the approximate nature of the electrode impedance estimates and some remaining unknown parasitic capacitances that led to current leakage. It was concluded that the proposed correction procedure for SIP measurements improved the accuracy of the phase measurements by an order of magnitude in the kHz frequency range. Further improvement of this accuracy requires a method to accurately estimate parasitic capacitances in situ.

  18. 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.

  19. The use of electrical impedance spectroscopy in the detection of cervical intraepithelial neoplasia.

    PubMed

    Abdul, S; Brown, B H; Milnes, P; Tidy, J A

    2006-01-01

    The objective of this study was to assess the performance of cervical impedance spectroscopy in the detection of cervical intraepithelial neoplasia (CIN) using the new MKIII impedance probe. A prospective observational study recruited women referred to colposcopy with an abnormal Papanicolaou smear. A pencil probe incorporating four gold electrodes was used to measure electrical impedance spectra from cervical epithelium. Colposcopy examinations, including probe positioning, were video recorded to allow for correlation between results obtained from colposcopic impression, histopathologic examination of colposcopic punch biopsies, and impedance measurements. Cervical impedance-derived parameters R, S, R/S, C, and Fc were assessed to see if significant difference in values obtained in CIN and normal epithelium existed. The performance of the probe in identifying women with CIN was also assessed. One hundred seventy-six women were recruited and 1168 points analyzed. Parameters R, S, and Fc showed significant separation of CIN or squamous intraepithelial lesion (SIL) from squamous, mature metaplastic, and columnar epithelium. Sensitivities of 74% and specificity of 53% can be achieved in identifying CIN 2/3 (High-grade SIL) in screened women. We conclude that cervical impedance spectrometry provides a potentially promising real-time screening tool for CIN with similar sensitivity and specificity to currently used screening tests. Further research is ongoing to develop the probe for potential clinical use.

  20. Transthoracic electrical impedance: artifacts associated with electrode movement.

    PubMed

    Hull, E T; Irie, T; Heemstra, H; Wildevuur, R H

    1978-01-01

    The applicability of transthoracic impedance measurements for estimating thoracic fluid volume and tidal volume is limited by large variations associated with electrode movement, repeated application of electrodes and inter-individual differences. These sources of variation were studied with a four-electrode impedance-measuring device in anaesthetized dogs. Electrode movement artifacts affecting both the resting expiratory value of impedance (Zo) and the respiratory change of impedance (deltaZ/VT) could be largely eliminated by rigidly fixing the distances between the current-supplying and the potential-sensing electrodes. The reproducibility of Zo and deltaZ/VT was found to be affected adversely by local conductivity changes in the skin induced by repeated removal of the glued electrodes. Inter-individual variations in Zo and deltaZ/VT correlated with the thickness of thoracic subcutaneous fat (r = 0.86) and thoracic circumference (r = -0.95) respectively. Correction for these sources of inter-individual variation allowed the standard deviations of Zo and deltaZ/VT to be reduced from 18% to 7% and from 51% to 17% of their respective mean values.

  1. Cell Electrical Impedance as a Novel Approach for Studies on Senescence Not Based on Biomarkers

    PubMed Central

    Cha, Jung-Joon; Park, Yangkyu; Yun, Joho; Kim, Hyeon Woo; Park, Chang-Ju; Kang, Giseok; Jung, Minhyun; Pak, Boryeong; Jin, Suk-Won

    2016-01-01

    Senescence of cardiac myocytes is frequently associated with heart diseases. To analyze senescence in cardiac myocytes, a number of biomarkers have been isolated. However, due to the complex nature of senescence, multiple markers are required for a single assay to accurately depict complex physiological changes associated with senescence. In single cells, changes in both cytoplasm and cell membrane during senescence can affect the changes in electrical impedance. Based on this phenomenon, we developed MEDoS, a novel microelectrochemical impedance spectroscopy for diagnosis of senescence, which allows us to precisely measure quantitative changes in electrical properties of aging cells. Using cardiac myocytes isolated from 3-, 6-, and 18-month-old isogenic zebrafish, we examined the efficacy of MEDoS and showed that MEDoS can identify discernible changes in electrical impedance. Taken together, our data demonstrated that electrical impedance in cells at different ages is distinct with quantitative values; these results were comparable with previously reported ones. Therefore, we propose that MEDoS be used as a new biomarker-independent methodology to obtain quantitative data on the biological senescence status of individual cells. PMID:27812531

  2. Focused impedance measurement (FIM). A new technique with improved zone localization.

    PubMed

    Rabbani, K S; Sarker, M; Akond, M H; Akter, T

    1999-04-20

    Conventional four-electrode impedance measurements (FEIM) cannot localize a zone of interest in a volume conductor. On the other hand, the recently developed electrical impedance tomography (EIT) system offers an image with reasonable resolution, but is complex and needs many electrodes. By placing two FEIM systems perpendicular to each other over a common zone at the center and combining the two results, it is possible to obtain enhanced sensitivity over this central zone. This is the basis of the proposed new method of focused impedance measurement (FIM). Sensitivity maps in both 2D and 3D show the desired improvement. A comparison of stomach-emptying studies also indicates the improvement achieved. This new method may be useful for impedance measurements of large organs like stomach, heart, and lungs. Being much simpler in comparison to EIT, multifrequency systems can be simply built for FIM. Besides, FIM may have utility in other fields like geology where impedance measurements are performed.

  3. 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

  4. 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

  5. Quantitative assessment of impedance tomography for temperature measurements in hyperthermia.

    PubMed

    Blad, B; Persson, B; Lindström, K

    1992-01-01

    The objective of this study is a non-invasive assessment of the thermal dose in hyperthermia. Electrical impedance tomography (EIT) has previously been given a first trial as a temperature monitoring method together with microwave-induced hyperthermia treatment, but it has not been thoroughly investigated. In the present work we have examined this method in order to investigate the correlation in vitro between the true spatial temperature distribution and the corresponding measured relative resistivity changes. Different hyperthermia techniques, such as interstitial water tubings, microwave-induced, laser-induced and ferromagnetic seeds have been used. The results show that it is possible to find a correlation between the measured temperature values and the tomographically measured relative resistivity changes in tissue-equivalent phantoms. But the uncertainty of the temperature coefficients, which has been observed, shows that the method has to be improved before it can be applied to clinical in vivo applications.

  6. Patterns of gas and liquid reflux during transient lower oesophageal sphincter relaxation: a study using intraluminal electrical impedance

    PubMed Central

    Sifrim, D; Silny, J; Holloway, R; Janssens, J

    1999-01-01

    Background—Belching has been proposed as a major mechanism underlying acid gastro-oesophageal reflux in normal subjects. However, the presence of oesophageal gas has not been measured directly but only inferred from manometry. 
Aims—To investigate, using intraluminal electrical impedance, the patterns of gas and liquid reflux during transient lower oesophageal sphincter (LOS) relaxations, the main mechanism of acid reflux in normal subjects. 
Methods—Impedance changes associated with the passage of gas were studied in vitro, and in vivo in cats. Oesophageal manometry, pH, and intraluminal electrical impedance measurements were performed in 11 normal subjects after a meal. 
Results—Gas reflux caused a sudden increase in impedance that propagated rapidly to the proximal oesophagus whereas liquid reflux induced a retrogressively propagated fall in impedance. Impedance showed gas or liquid reflux during most (102/141) transient LOS relaxations. When acid reflux occurred, impedance showed evidence of intraoesophageal retrograde flow of liquid in the majority (78%) of events. Evidence of gas retroflow was found in almost half (47%) of acid reflux episodes. When present together, however, liquid preceded gas on 44% of occasions. Overall, gas reflux occurred as the initial event in only 25% of acid reflux episodes. 
Conclusions—These findings suggest that in upright normal subjects, although belching can precipitate acid reflux, most acid reflux occurs as a primary event. 

 Keywords: belching; gastro-oesophageal reflux disease; oesophageal manometry; intraluminal electrical impedance; lower oesophageal sphincter PMID:9862825

  7. Transverse impedance measurement in RHIC and the AGS

    SciTech Connect

    Biancacci, Nicolo; Blaskiewicz, M.; Dutheil, Y.; Liu, C.; Mernick, M.; Minty, M.; White, S. M.

    2014-05-12

    The RHIC luminosity upgrade program aims for an increase of the polarized proton luminosity by a factor 2. To achieve this goal a significant increase in the beam intensity is foreseen. The beam coupling impedance could therefore represent a source of detrimental effects for beam quality and stability at high bunch intensities. For this reason it is essential to quantify the accelerator impedance budget and the major impedance sources, and possibly cure them. In this MD note we summarize the results of the 2013 transverse impedance measurements in the AGS and RHIC. The studies have been performed measuring the tune shift as a function of bunch intensity and deriving the total accelerator machine transverse impedance. For RHIC, we could obtain first promising results of impedance localization measurements as well.

  8. Modeling of lung's electrical impedance using fractional calculus for analysis of heat generation during RF-ablation.

    PubMed

    Yamazaki, Nozomu; Kobayashi, Yo; Kikuchi, Hayato; Isobe, Yosuke; Lu, XiaoWei; Miyashita, Tomoyuki; Fujie, Masakatsu G

    2014-01-01

    Recently, Radio Frequency Ablation (RFA) is becoming a popular therapy for various cancers such as liver, breast, or lung cancer. RFA is one kinds of thermal therapy. However, it has been often reported about excessive ablation or non-ablation due to difficult control of ablation energy. In order to solve these difficulties, we have been proposed robotized RF-ablation system for precise cancer treatment. We have been tried to control heat energy by control of electromagnetic-wave frequency. In this paper, we reported about relation among electrical impedance of lung, lung's internal air volumes, and heat energy by use of electromagnetic-wave. In case of RFA for lung cancer, heat energy depends on electrical impedance and lung's internal air volumes. Electrical impedance has the dependence of electromagnetic-wave frequency and the dependence of lung's internal air volumes. Therefore, firstly we considered about fractional calculus model between lung's internal air volumes and electrical impedance. Secondly, we measured electric impedance frequency characteristic of lung with change of lung's internal air volumes. The measured and modeled results showed that use of fractional calculus realized high accurate model for electrical impedance of lung. And, from the results of numerical analysis of heat energy, it is supposed that control of electromagnetic-wave frequency has a small effectiveness for lung tissue ablation even if lung includes abundant air.

  9. Influence of sodium chloride content in electrolyte solution on electrochemical impedance measurements of human dentin

    PubMed Central

    Eldarrat, Aziza; High, Alec; Kale, Girish

    2017-01-01

    Background: The aim of this study was to investigate the influence of sodium chloride (NaCl) content in electrolyte solution on electrochemical impedance measurements of human dentin by employing electrochemical impedance spectroscopy. Materials and Methods: Dentin samples were prepared from extracted molars. Electrochemical impedance measurements were carried out over a wide frequency range (0.01Hz-10MHz). After measurements, samples were characterized using scanning electron microscopy. Results: Electrochemical impedance measurements showed that the mean values of dentin electrical resistance were 4284, 2062, 1336, 53 and 48kΩ at different NaCl contents in electrolyte solution. One-way ANOVA test of mean values of dentin electrical resistance revealed a significant difference (P < 0.0001) as a function of NaCl content in electrolyte solution. Comparing electrical resistance values of dentin samples at 0.05% w/v and 0.9% w/v concentrations were found to be significantly different (P < 0.05 at 95% confidence level). Scanning electron microscopy revealed structure of dentin sample with intertubular dentin matrix and distribution of patent dentinal tubules. Conclusion: This in vitro study indicated, through electrochemical impedance spectroscopy measurements, that electrical resistance of dentin was affected by the concentration of NaCl in electrolyte solution. It is clear from the current study that NaCl concentration in electrolyte solution has a marked influence on dentin electrical resistance. Therefore, this baseline data need to be considered in any future study on dental samples. PMID:28348614

  10. Electric cell-substrate impedance sensing for the quantification of endothelial proliferation, barrier function, and motility.

    PubMed

    Szulcek, Robert; Bogaard, Harm Jan; van Nieuw Amerongen, Geerten P

    2014-03-28

    Electric Cell-substrate Impedance Sensing (ECIS) is an in vitro impedance measuring system to quantify the behavior of cells within adherent cell layers. To this end, cells are grown in special culture chambers on top of opposing, circular gold electrodes. A constant small alternating current is applied between the electrodes and the potential across is measured. The insulating properties of the cell membrane create a resistance towards the electrical current flow resulting in an increased electrical potential between the electrodes. Measuring cellular impedance in this manner allows the automated study of cell attachment, growth, morphology, function, and motility. Although the ECIS measurement itself is straightforward and easy to learn, the underlying theory is complex and selection of the right settings and correct analysis and interpretation of the data is not self-evident. Yet, a clear protocol describing the individual steps from the experimental design to preparation, realization, and analysis of the experiment is not available. In this article the basic measurement principle as well as possible applications, experimental considerations, advantages and limitations of the ECIS system are discussed. A guide is provided for the study of cell attachment, spreading and proliferation; quantification of cell behavior in a confluent layer, with regard to barrier function, cell motility, quality of cell-cell and cell-substrate adhesions; and quantification of wound healing and cellular responses to vasoactive stimuli. Representative results are discussed based on human microvascular (MVEC) and human umbilical vein endothelial cells (HUVEC), but are applicable to all adherent growing cells.

  11. Impedance measurements for detecting pathogens attached to antibodies

    DOEpatents

    Miles, Robin R.; Venkateswaran, Kodumudi S.; Fuller, Christopher K.

    2004-12-28

    The use of impedance measurements to detect the presence of pathogens attached to antibody-coated beads. In a fluidic device antibodies are immobilized on a surface of a patterned interdigitated electrode. Pathogens in a sample fluid streaming past the electrode attach to the immobilized antibodies, which produces a change in impedance between two adjacent electrodes, which impedance change is measured and used to detect the presence of a pathogen. To amplify the signal, beads coated with antibodies are introduced and the beads would stick to the pathogen causing a greater change in impedance between the two adjacent electrodes.

  12. Linearity of electrical impedance tomography during maximum effort breathing and forced expiration maneuvers.

    PubMed

    Ngo, Chuong; Leonhardt, Steffen; Zhang, Tony; Lüken, Markus; Misgeld, Berno; Vollmer, Thomas; Tenbrock, Klaus; Lehmann, Sylvia

    2017-01-01

    Electrical impedance tomography (EIT) provides global and regional information about ventilation by means of relative changes in electrical impedance measured with electrodes placed around the thorax. In combination with lung function tests, e.g. spirometry and body plethysmography, regional information about lung ventilation can be achieved. Impedance changes strictly correlate with lung volume during tidal breathing and mechanical ventilation. Initial studies presumed a correlation also during forced expiration maneuvers. To quantify the validity of this correlation in extreme lung volume changes during forced breathing, a measurement system was set up and applied on seven lung-healthy volunteers. Simultaneous measurements of changes in lung volume using EIT imaging and pneumotachography were obtained with different breathing patterns. Data was divided into a synchronizing phase (spontaneous breathing) and a test phase (maximum effort breathing and forced maneuvers). The EIT impedance changes correlate strictly with spirometric data during slow breathing with increasing and maximum effort ([Formula: see text]) and during forced expiration maneuvers ([Formula: see text]). Strong correlations in spirometric volume parameters [Formula: see text] ([Formula: see text]), [Formula: see text]/FVC ([Formula: see text]), and flow parameters PEF, [Formula: see text], [Formula: see text], [Formula: see text] ([Formula: see text]) were observed. According to the linearity during forced expiration maneuvers, EIT can be used during pulmonary function testing in combination with spirometry for visualisation of regional lung ventilation.

  13. 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.

  14. 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.

  15. Estimation of postmortem interval using an electric impedance spectroscopy technique: a preliminary study.

    PubMed

    Mao, Shiwei; Dong, Xiuzhen; Fu, Feng; Seese, Ronald R; Wang, Zhenyuan

    2011-09-01

    The objective of this study was to develop a rapid method for the estimation of postmortem interval (PMI) using electric impedance spectroscopy. Postmortem rat spleens were studied at 10°C, 20°C, and 30°C; The results obtained demonstrated that postmortem interval negatively correlated with the absolute value of Im Z(//) (capacitive reactance component) in electrical impedance. This suggests that electric impedance spectroscopy may be a sensitive tool to determine the postmortem interval.

  16. Controlling the electrical impedance of nanomechanical oscillators by electromigration

    NASA Astrophysics Data System (ADS)

    Sun, Fengpei; Zou, Jie; Chan, Ho Bun

    2015-03-01

    Detection of nanomechanical motion is of fundamental and practical interests. For doubly clamped nanobeams, a common method is the magnetomotive reflection technique. However, this technique usually suffers from large signal background due to the mismatch of the electrical resistance (Re) of the oscillators to the impedance (50ohm usually) of the cables for detection. The large signal background precludes the possibility of driving the device into self-sustaining oscillations using a phase-locked loop. We develop a reproducible method of minimizing the signal background in the magnetomotive reflection technique. A gold nanowire with a junction in the middle is fabricated on the top of a doubly-clamped SixNy nanobeam via e-beam lithography. By passing a large direct current through the nanowire, migration of the gold atoms around the junction is activated due to the heat dissipated. An analog feedback loop is designed to maintain a stable process of electromigration until the target Re is reached. Initially Re is smaller than 50ohm. The motional impedance of the nanowire shifts the total impedance closer to 50ohm so that the resonance of the nanobeam appears as a dip on a large background in the amplitude spectrum. As Re is increased to near 50ohm, the background reaches a minimum, and the resonance of the nanobeam turns into a peak. Self-sustaining oscillations of the nanobeam are successfully achieved via a phase-locked loop in this case. As Re is further increased, the background becomes higher again. The dependence of the background signal on Re agrees with calculations.

  17. Crosstalk Compensation for a Rapid, Higher Resolution Impedance Spectrum Measurement

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; David M. Rose; William H. Morrison; Chester G. Motloch

    2012-03-01

    Batteries and other energy storage devices are playing larger roles in various industries (e.g., military, automotive, electric utilities, etc.) as the U.S. seeks to reduce its dependence on foreign energy resources. As such, there exists a significant need for accurate, robust state-of-health assessment techniques. Present techniques tend to focus on simple, passive monitoring of voltage and current at a given ambient temperature. However, this approach has the disadvantage of ignoring key elements of health, that is, changes in resistance growth and power fade. Impedance spectroscopy is considered a useful laboratory tool in gauging changes in the resistance and power performance, but it has not been widely considered as an onboard diagnostic tool due to the length of time required to complete the measurement. Cross-Talk Compensation (CTC) is a novel approach that enables rapid, high resolution impedance spectra measurements using a hardware platform that could be designed as an embedded system. This input signal consists of a sum-of-sines excitation current that has a known frequency spread and a duration of one period of the lowest frequency. The voltage response is then captured at a sufficiently fast sample rate. Previously developed rapid impedance spectrum measurement techniques either required a longer excitation signal or a sum-of-sines signal that was separated by harmonic frequencies to reduce or eliminate, respectively, the cross-talk interference in the calculated results. The distinct advantage of CTC, however, is that non-harmonic frequencies can now be included within the excitation signal while still keeping the signal duration at one period of the lowest frequency. Since the frequency spread of the input signal is known, the crosstalk interference between sinusoidal signals within the sum-of-sines at a given frequency of interest can be pre-determined and assigned to an error matrix. Consequently, the real and imaginary components of the

  18. Electrochemical impedance measurement of a carbon nanotube probe electrode

    NASA Astrophysics Data System (ADS)

    Inaba, Akira; Takei, Yusuke; Kan, Tetsuo; Matsumoto, Kiyoshi; Shimoyama, Isao

    2012-12-01

    We measured and analyzed the electrochemical impedance of carbon nanotube (CNT) probe electrodes fabricated through the physical separation of insulated CNT bridges. The fabricated CNT electrodes were free-standing CNTs that were completely covered with an insulator, except for their tips. Typical dimensions of the nanoelectrodes were 1-10 nm in CNT diameter, 80-300 nm in insulator diameter, 0.5-4 μm in exposed CNT length and 1-10 μm in probe length. The electrochemical impedance at frequencies ranging from 40 Hz to 1 MHz was measured in physiological saline. The measured impedance of the CNT electrode was constant at 32 MΩ at frequencies below 1 kHz and was inversely proportional to frequency at frequencies above 10 kHz. By means of comparison with the parasitic capacitive impedance of the insulator membrane, we confirmed that the electrode was sufficiently insulated such that the measured constant impedance was given by the exposed CNT tip. Consequently, we can use the CNT electrode for highly localized electrochemical impedance measurements below 1 kHz. Considering an equivalent circuit and the nanoscopic dimensions of the CNT electrode, we demonstrated that the constant impedance was governed by diffusion impedance, whereas the solution resistance, charge-transfer resistance and double-layer capacitance were negligible.

  19. Measurement of Single-Cell Deformability Using Impedance Analysis on Microfluidic Chip

    NASA Astrophysics Data System (ADS)

    Kim, Dongil; Choi, Eunpyo; Choi, Sung Sik; Lee, Sangho; Park, Jungyul; Yun, Kwang-Seok

    2010-12-01

    In this paper, we propose a microfluidic chip that measures the deformability of single cells by an impedance measurement method. The proposed chip is designed to differentiate the deformability of various cells by measuring the length of their stretched membrane indirectly according to the variation of the impedance after applying aspiration pressure to the cell membrane. The length of the stretched cell membrane is proportional to the applied pressure. Lengths of 18 and 21 µm were observed at the same suction pressure for human breast normal cells (MCF-10A) and caner cells (MCF-7), respectively. Electrical measurement was performed using an impedance analyzer at various frequencies. Results revealed that the impedance measurement method can be used to analyze the biomechanical characteristics of single cells, which indicates the state of malignancy of cells.

  20. Recent Progress on the Factorization Method for Electrical Impedance Tomography

    PubMed Central

    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

  1. Multispectral Electrical Impedance Tomography using Optimization over Manifolds

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    Electrical impedance tomography under spectral constraints uses a material basis decomposition to combine the different information embedded in the tissue spectra. This approach offers an alternative to static imaging while benefiting from systemic error cancellation using difference data. It suits well cases where no prior solution is known and the contrast lies entirely between frequencies, e.g. to diagnose acute stroke or cancer. In this work, a computational framework is presented to deal with the extra frequency dimensions and the constraints during reconstruction. A fraction volume approach is demonstrated with explicit Euclidean gradient, usage of a finite volume element solver and minimization over the oblique manifold. It is applied to synthetic data. Parameter estimations are compared between a monofrequency inversion and the proposed multispectral implementation. Results suggest that the proposed workflow enables to reduce the computational workload of multispectral inversion while ensuring valid proportions of materials within each control volume.

  2. Sensing fluid viscosity and density through mechanical impedance measurement using a whisker transducer

    NASA Astrophysics Data System (ADS)

    Ju, Feng; Ling, Shih-Fu

    2013-05-01

    This paper presents a new technique for fluid viscosity and density sensing through measuring the mechanical impedance of the fluid load applied on a sphere. A piezoelectric whisker transducer (WT) is proposed which acts simultaneously as both the actuator to excite the sphere tip to oscillate in the fluid and the sensor to measure the force, velocity and mechanical impedance. The relationship between mechanical impedance of the fluid load and electrical impedance of the WT is derived based on a transduction matrix model which characterizes the electro-mechanical transduction process of the WT in both directions. The mechanical impedance is further related to the fluid viscosity and density using a theoretical model. The establishment of this fluid-mechanical-electrical relationship allows the WT to extract the fluid viscosity and density conveniently and accurately just from its electrical impedance. Experimental studies are carried out to calibrate the WT and test its performance using glycerol-water mixtures. It is concluded that the WT is capable of providing results comparable to those of standard viscometers within a wide measurement range due to its low working frequency and large vibration amplitude. Its unique self-actuation-and-sensing feature makes it a suitable solution for online fluid sensing.

  3. Effect of Feeding and Suction on Gastric Impedance Spectroscopy Measurements.

    PubMed

    Beltran, Nohra E; Sánchez-Miranda, Gustavo; Sacristan, Emilio

    2015-01-01

    A specific device and system has been developed and tested for clinical monitoring of gastric mucosal reactance in the critically ill as an early warning of splanchnic hypoperfusion associated with shock and sepsis. This device has been proven effective in clinical trials and is expected to become commercially available next year. The system uses a combination nasogastric tube and impedance spectroscopy probe as a single catheter. Because this device has a double function, the question is: Does enteral feeding or suction affect the gastric reactance measurements? This study was designed to evaluate the effect of feeding and suction on the measurement of gastric impedance spectroscopy in healthy volunteers. Impedance spectra were obtained from the gastric wall epithelia of 18 subjects. The spectra were measured for each of the following conditions: postinsertion of gastric probe, during active suction, postactive suction, and during enteral feeding (236 ml of nutritional supplement). Impedance spectra were reproducible in all volunteers under all conditions tested. There was a slight increase in impedance parameters after suction, and a decrease in impedance after feeding; however, these observed differences were insignificant compared to patient-to-patient variability, and truly negligible compared with previously observed changes associated with splanchnic ischemia in critically ill patients. Our results demonstrate that suction or feeding when using the impedance spectro-metry probe/nasogastric tube does not significantly interfere with gastric impedance spectrometer measurements.

  4. Interdigitated microelectrode-based microchip for electrical impedance spectroscopic study of oral cancer cells.

    PubMed

    Mamouni, Jaouad; Yang, Liju

    2011-12-01

    In this study, electric/electrochemical impedance spectroscopy and cyclic voltammetry were used to study the cellular activities of oral cancer cell line CAL 27, including the kinetics of cell adhesion, spreading, and cell proliferation on interdigitated microelectrodes (IMEs). Impedance spectra of CAL 27 cells on IMEs electrodes were obtained in cell growth medium and in 0.1 M PBS with 50 mM [Fe(CN)₆]³⁻/⁴⁻ as redox probe. Equivalent circuits were used to model both cases. In cell growth medium, impedance spectra allowed us to analyze the changes in capacitance and resistance due to cell attachment on the IMEs over the entire experiment period. It was found that cell spreading caused the most significant decrease in capacitance component and slight increase in resistance component. Impedance change at given frequencies (between 10 kHz to 100 kHz) was found to be linearly increased with increasing cell number of CAL 27 on the IMEs. In comparison with non-cancer oral epithelial cells (Het-1A), at equal cell number, cancer cells always generated impedance several folds higher than that of non-cancer cells. In the presence of [Fe(CN)₆]³⁻/⁴⁻, impedance spectra allowed us to analyze the change in electron transfer resistance of IMEs due to cell attachment, in which an increase trend was observed at 24 h with increasing cell number from 2500 cells to 10,000 cells on IMEs. Double layer capacitance was also affected by cell attachment, and a decrease in double layer capacitance was observed with increasing cell number on the electrodes. Cyclic voltammetric measurements correlated well with the impedance results. The results of this study demonstrated the use of electrochemical approaches to obtain and understand cellular behaviors/activities of oral cancer cells, potentially providing useful tools for cancer cell research.

  5. Grinding process monitoring based on electromechanical impedance measurements

    NASA Astrophysics Data System (ADS)

    Marchi, Marcelo; Guimarães Baptista, Fabricio; de Aguiar, Paulo Roberto; Bianchi, Eduardo Carlos

    2015-04-01

    Grinding is considered one of the last processes in precision parts manufacturing, which makes it indispensable to have a reliable monitoring system to evaluate workpiece surface integrity. This paper proposes the use of the electromechanical impedance (EMI) method to monitor the surface grinding operation in real time, particularly the surface integrity of the ground workpiece. The EMI method stands out for its simplicity and for using low-cost components such as PZT (lead zirconate titanate) piezoelectric transducers. In order to assess the feasibility of applying the EMI method to the grinding process, experimental tests were performed on a surface grinder using a CBN grinding wheel and a SAE 1020 steel workpiece, with PZT transducers mounted on the workpiece and its holder. During the grinding process, the electrical impedance of the transducers was measured and damage indices conventionally used in the EMI method were calculated and compared with workpiece wear, indicating the surface condition of the workpiece. The experimental results indicate that the EMI method can be an efficient and cost-effective alternative for monitoring precision workpieces during the surface grinding process.

  6. Static imaging of the electrical impedance tomography on cylinder physical phantom.

    PubMed

    Liu, Ruigang; Fu, Feng; You, Fusheng; Shi, Xuetao; Dong, Xiuzhen

    2015-01-01

    Static imaging of the electrical impedance tomography can obtain the absolute electrical conductivity distribution at one section of the subject. The test is performed on a cylinder physical phantom in which slim rectangle, hollow cylinder, small rectangle or three cylinders are selected to simulate complex conductivity perturbation objects. The measurement data is obtained by a data acquisition system with 32 compound electrodes. A group of static images of conductivity distribution in the cylinder phantom are reconstructed by the modified Newton-Raphson algorithm with two kinds of regularization methods. The results show correct position, size, conductivity difference, and similar shape of the perturbation objects in the images.

  7. Electric impedance sensing during the inhibition of cell-cell adhesion.

    PubMed

    Wiertz, R F; Rutten, W C; Marani, E

    2008-01-01

    Electric cell impedance sensing (ECIS) was used to monitor the change of in vitro neuron-neuron adhesion in response to the blocking of N-Cam, N-Cadherin and L1. ECIS is a method in which cell morphology and cell mobility can be indirectly measured by changes in intercellular resistance. Antibodies and soluble extracellular domains of the cell adhesion molecules N-Cam, N-Cadherin and L1 were used as blockers of these adhesion molecules on the cell surface. In a 96 hour aggregation assay on a low adhesive substrate, the effect of mentioned blockers on the aggregation was investigated. The N-Cadherin antibody showed effective in aggregation inhibition at concentrations of 3 and 10 micrograms/ml. Up to 96 hours no aggregation occurred. A similar effect was achieved by the N-Cadherin protein, although less distinct. Blocking of N-CAM and L1 revealed no inhibition of aggregation. Results from impedance measurements correspond to those of the aggregation assays. The neuron-neuron adhesion in monolayers was inhibited by blocking of cell adhesion molecules and monitored by ECIS. Impedances of neuron covered electrodes were significantly lower in the presence of N-Cadherin antibody and protein at concentrations of 1, 3 and 10 micrograms/ml, indicating a less profound binding between adjacent neuron.The results from both the aggregation assays and the impedance measurements demonstrate the applicability of CAM blocking for the regulation of culture topography.

  8. Design rule for optimization of microelectrodes used in electric cell-substrate impedance sensing (ECIS).

    PubMed

    Price, Dorielle T; Rahman, Abdur Rub Abdur; Bhansali, Shekhar

    2009-03-15

    This paper presents an experimentally derived design rule for optimization of microelectrodes used in electric cell-substrate impedance sensing (ECIS) up to 10MHz. The effect of change in electrode design (through electrode sensor area, lead trace widths, and passivation coating thickness) on electrode characteristics was experimentally evaluated using electrochemical impedance spectroscopy (EIS) measurements and analyzed using equivalent circuit models. A parasitic passivation coating impedance was successfully minimized by designing electrodes with either a thicker passivation layer or a smaller lead trace area. It was observed that the passivated lead trace area to passivation coating thickness ratio has a critical value of 5.5, under which the impedance contribution of the coating is minimized. The optimized design of ECIS-based microelectrode devices reported in this work will make it possible to probe the entire beta dispersion region of adherent biological cell layers by reducing measurement artifacts and improving the quality of data across the beta-dispersion region. The new design will enable the use of the commonly used ECIS technique to measure real-time cellular properties in high frequency ranges (beta dispersion) that was not possible thus far.

  9. 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.

  10. 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.

  11. Electric impedance of human embryonic stem cell-derived retinal pigment epithelium.

    PubMed

    Onnela, Niina; Savolainen, Virpi; Juuti-Uusitalo, Kati; Vaajasaari, Hanna; Skottman, Heli; Hyttinen, Jari

    2012-02-01

    The barrier properties of epithelium are conventionally defined by transepithelial resistance (TER). TER provides information about the tightness of the epithelium. Electrical impedance spectroscopy (EIS) provides additional information regarding cell membrane properties, such as changes in electric capacitance and possible parallel or serial pathways that may correlate with the morphology of the cell layer. This study presents EIS of retinal pigment epithelial (RPE) cell model of the putative RPE differentiated from human embryonic stem cells (hESC-RPE). The generally utilized RPE cell model, ARPE-19, was used as immature control. The measured EIS was analyzed by fitting an equivalent electrical circuit model describing the resistive and capacitive properties of the RPE. Our results indicated that TER of hESC-RPE cells was close to the values of human RPE presented in the literature. This provides evidence that the stem cell-derived RPE in vitro can reach high-barrier function. Furthermore, hESC-RPE cells produced impedance spectra that can be modeled by the equivalent circuit of one time constant. ARPE-19 cells produced low-barrier properties, that is, an impedance spectra that suggested poor maturation of ARPE-19 cells. To conclude, EIS could give us means for non-invasively estimating the functionality and maturation of differentiated-RPE cells.

  12. Automated electrical impedance technique for rapid enumeration of fecal coliforms in effluents from sewage treatment plants.

    PubMed

    Silverman, M P; Munoz, E F

    1979-03-01

    Fecal coliforms growing in a selective lactose-based broth medium at 44.5 degrees C generate a change in the electrical impedance of the culture relative to a sterile control when populations reach 10(6) to 10(7) per ml. The ratio of these changes was measured automatically, and the data were processed by computer. A linear relation was found between the log10 of the number of fecal coliforms in an inoculum and the time required for an electrical impedance ratio signal to be detected. Pure culture inocula consisting of 100 fecal coliforms in log phase or stationary phase were detected in 6.5 and 7.7 h, respectively. Standard curves of log10 fecal coliforms in wastewater inocula versus detection time, based on samples collected at a sewage treatment plant over a 4-month period, were found to vary from one another with time. Nevertheless, detection times were rapid and ranged from 5.8 to 7.9 h for 200 fecal coliforms to 8.7 to 11.4 h for 1 fecal coliform. Variations in detection times for a given number of fecal coliforms were also found among sewage treatment plants. A strategy is proposed which takes these variations into account and allows for rapid, automated enumeration of fecal coliforms in wastewater by the electrical impedance ratio technique.

  13. Automated electrical impedance technique for rapid enumeration of fecal coliforms in effluents from sewage treatment plants.

    PubMed Central

    Silverman, M P; Munoz, E F

    1979-01-01

    Fecal coliforms growing in a selective lactose-based broth medium at 44.5 degrees C generate a change in the electrical impedance of the culture relative to a sterile control when populations reach 10(6) to 10(7) per ml. The ratio of these changes was measured automatically, and the data were processed by computer. A linear relation was found between the log10 of the number of fecal coliforms in an inoculum and the time required for an electrical impedance ratio signal to be detected. Pure culture inocula consisting of 100 fecal coliforms in log phase or stationary phase were detected in 6.5 and 7.7 h, respectively. Standard curves of log10 fecal coliforms in wastewater inocula versus detection time, based on samples collected at a sewage treatment plant over a 4-month period, were found to vary from one another with time. Nevertheless, detection times were rapid and ranged from 5.8 to 7.9 h for 200 fecal coliforms to 8.7 to 11.4 h for 1 fecal coliform. Variations in detection times for a given number of fecal coliforms were also found among sewage treatment plants. A strategy is proposed which takes these variations into account and allows for rapid, automated enumeration of fecal coliforms in wastewater by the electrical impedance ratio technique. PMID:378128

  14. Insulator-based DEP with impedance measurements for analyte detection

    DOEpatents

    Davalos, Rafael V.; Simmons, Blake A.; Crocker, Robert W.; Cummings, Eric B.

    2010-03-16

    Disclosed herein are microfluidic devices for assaying at least one analyte specie in a sample comprising at least one analyte concentration area in a microchannel having insulating structures on or in at least one wall of the microchannel which provide a nonuniform electric field in the presence of an electric field provided by off-chip electrodes; and a pair of passivated sensing electrodes for impedance detection in a detection area. Also disclosed are assay methods and methods of making.

  15. Measurement and simulation of the RHIC abort kicker longitudinal impedence

    SciTech Connect

    Abreu,N.P.; Hahn,H.; Choi, E.

    2009-09-01

    In face of the new upgrades for RHIC the longitudinal impedance of the machine plays an important role in setting the threshold for instabilities and the efficacy of some systems. In this paper we describe the measurement of the longitudinal impedance of the abort kicker for RHIC as well as computer simulations of the structure. The impedance measurement was done by the S{sub 21} wire method covering the frequency range from 9 kHz to 2.5 GHz. We observed a sharp resonance peak around 10 MHz and a broader peak around 20 MHz in both, the real and imaginary part, of the Z/n. These two peaks account for a maximum imaginary longitudinal impedance of j15 {Omega}, a value an order of magnitude larger than the estimated value of j0.2 {Omega}, which indicates that the kicker is one of the main sources of longitudinal impedance in the machine. A computer model was constructed for simulations in the CST MWS program. Results for the magnet input and the also the beam impedance are compared to the measurements. A more detail study of the system properties and possible changes to reduce the coupling impedance are presented.

  16. Comparison of impedance measurements near the skin of newborns and adults.

    PubMed

    Amm, Bruce; Kao, Tzu-Jen; Newell, Jonathan; Isaacson, David; Saulnier, Gary; Shoudy, David; Boverman, Greg; Sahni, Rakesh; Weindler, Marilyn; Chong, David; DiBardino, David; Davenport, David; Ashe, Jeffrey

    2016-06-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technology that has been extensively studied for monitoring lung function of neonatal and adult subjects, especially in neonatal intensive care unit (NICU) and intensive care unit (ICU) environments. The sources of the total impedance in these applications include internal organs, near-boundary tissues, electrode-skin impedance, electrodes and conducting wires. This total impedance must be considered for system design and setting voltage gain since it will contribute to the measured voltage. To adapt a single instrument for use on infants and adults, we studied the difference between the impedance near the skin in both classes of patients. We used a simultaneous multi-source EIT (SMS-EIT) system to make impedance measurements. Characteristic resistance was calculated for two different current patterns: one that is more sensitive to boundary region impedance and another that is more sensitive to interior changes. We present ratios of these resistances to assess the relative contribution of near-skin effects to the overall impedance. Twenty adult ICU subjects (10 male, 10 female, age: 49.05  ±  16.32 years (mean  ±  standard deviation)) and 45 neonates (23 male, 22 female, gestational age: 37.67  ±  2.11 weeks, postnatal age, 2.56  ±  2.67 d) were studied at Columbia University Medical Center. Impedance measurements at 10 kHz were collected for approximately one hour from each subject. The characteristic resistance ratio for each subject was computed and analyzed. The result shows the impedance at or near the skin of newborns is significantly higher than in adult subjects.

  17. Damage detection technique by measuring laser-based mechanical impedance

    SciTech Connect

    Lee, Hyeonseok; Sohn, Hoon

    2014-02-18

    This study proposes a method for measurement of mechanical impedance using noncontact laser ultrasound. The measurement of mechanical impedance has been of great interest in nondestructive testing (NDT) or structural health monitoring (SHM) since mechanical impedance is sensitive even to small-sized structural defects. Conventional impedance measurements, however, have been based on electromechanical impedance (EMI) using contact-type piezoelectric transducers, which show deteriorated performances induced by the effects of a) Curie temperature limitations, b) electromagnetic interference (EMI), c) bonding layers and etc. This study aims to tackle the limitations of conventional EMI measurement by utilizing laser-based mechanical impedance (LMI) measurement. The LMI response, which is equivalent to a steady-state ultrasound response, is generated by shooting the pulse laser beam to the target structure, and is acquired by measuring the out-of-plane velocity using a laser vibrometer. The formation of the LMI response is observed through the thermo-mechanical finite element analysis. The feasibility of applying the LMI technique for damage detection is experimentally verified using a pipe specimen under high temperature environment.

  18. Optimally tuned resonant negative capacitance for piezoelectric shunt damping based on measured electromechanical impedance

    NASA Astrophysics Data System (ADS)

    Salloum, Rogério; Heuss, Oliver; Götz, Benedict; Mayer, Dirk

    2015-04-01

    In this paper, a new tuning method for shunt damping with a series resistance, inductance and negative capacitance is proposed and its validity is investigated. It is based on the measured electromechanical impedance of a piezoelectric system, which is represented through an equivalent electrical circuit that takes into account the characteristics of the piezoelectric transducer and the host structure. Afterwards, an additional circuit representing the shunt is connected and the Norton equivalent impedance is obtained at the terminals that represent the mechanical mode of interest. During the tuning process, the optimal shunt parameters are found by minimizing the maximum absolute value of the Norton equivalent impedance over a defined frequency range through a numerical optimization. Taking benefit from the analogy between electrical impedance and mechanical admittance, the minimization of different mechanical responses (displacement, velocity or acceleration) is also proposed and the different optimum shunt parameters obtained are compared. In view of real technical applications, this method allows the integration of a real negative capacitance circuit, i.e., a negative impedance converter, rather than an ideal component. It is thus possible to use the impedance of this circuit and optimize the individual component values. Since this method is based on one simple measurement, it can be applied to arbitrary structures without the need of complex dynamic tests or expensive finite elements calculations. Finally, an experimental analysis is carried out in order to compare the damping performance of the proposed method and the conventional analytical method that minimizes a mechanical frequency response function.

  19. A physics-based model of the electrical impedance of ionic polymer metal composites

    NASA Astrophysics Data System (ADS)

    Cha, Youngsu; Aureli, Matteo; Porfiri, Maurizio

    2012-06-01

    In this paper, we analyze the chemoelectrical behavior of ionic polymer metal composites (IPMCs) in the small voltage range with a novel hypothesis on the charge dynamics in proximity of the electrodes. In particular, we homogenize the microscopic properties of the interfacial region through a so-called composite layer which extends between the polymer membrane and the metal electrode. This layer accounts for the dissimilar properties of its constituents by describing the charge distribution via two species of charge carriers, that is, electrons and mobile counterions. We model the charge dynamics in the IPMC by adapting the multiphysics formulation based on the Poisson-Nernst-Planck (PNP) framework, which is enriched through an additional term to capture the electron transport in the composite layer. Under the hypothesis of small voltage input, we use the linearized PNP model to derive an equivalent IPMC circuit model with lumped elements. The equivalent model comprises a resistor connected in series with the parallel of a capacitor and a Warburg impedance element. These elements idealize the phenomena of charge build up in the double layer region and the faradaic impedance related to mass transfer, respectively. We validate the equivalent model through measurements on in-house fabricated samples addressing both IPMC step response and impedance, while assessing the influence of repeated plating cycles on the electrical properties of IPMCs. Experimental results are compared with theoretical findings to identify the equivalent circuit parameters. Findings from this study are compared with alternative impedance models proposed in the literature.

  20. Ionic conductivity and electrical relaxation of nanocrystalline scandia-stabilized c-zirconia using complex impedance analysis

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Manna, I.

    2008-07-01

    A solid solution of 8 mol% of scandia-stabilized cubic-zirconia (8ScSZ) has been prepared by co-precipitation technique. The synthesized powder has an average crystallite size ∼40 nm, surface area of 8.49 m 2/g, and agglomerated particle size of 150 nm. The activation energy of 8ScSZ has been calculated from impedance loss spectra; electrical modulus spectra are in the range of 0.90-1.30 eV. The frequency and temperature-dependent conductivities and impedance were measured in range of 50 Hz-1 MHz and 300-900 K, respectively. Complex impedance spectra, complex modulus formalism and complex conductivity spectra have been carefully analyzed in order to separate the grain, grain boundary and electrode-electrolyte effects. Analysis of ac impedance data using complex impedance indicates a typical negative temperature coefficient of resistance (NTCR) behavior of the materials. The intrinsic conductivity is mainly due to hopping of mobile ions among the available localized site. Relaxation time obtained from complex conductivity spectra are matched well with the impedance loss and modulus loss spectra. Impedance analysis suggests the presence of temperature-dependent electrical relaxation process in the material.

  1. A microchip integrating cell array positioning with in situ single-cell impedance measurement.

    PubMed

    Guo, Xiaoliang; Zhu, Rong; Zong, Xianli

    2015-10-07

    This paper presents a novel microarray chip integrating cell positioning with in situ, real-time and long-time impedance measurement on a single cell. The microchip integrates a plurality of quadrupole-electrode units (termed positioning electrodes) patterned into an array with pairs of planar electrodes (termed measuring electrodes) located at the centers of each quadrupole-electrode unit. The positioning electrodes are utilized to trap and position living cells onto the measuring electrodes based on negative dielectrophoresis (nDEP), while the measuring electrodes are used to measure impedances of the trapped single cells. Each measuring electrode has a small footprint area of 7 × 7 μm(2) to ensure inhabiting only one single cell on it. However, the electrode with a small surface area has a low double-layer capacitance when it is immersed in a liquid solution, thus generating a large double-layer impedance, which reduces the sensitivity for impedance measurement on the single cell. To enlarge the effective surface areas of the measuring electrodes, a novel surface-modification process is proposed to controllably construct gold nanostructures on the surfaces of the measuring electrodes while the positioning electrodes are unstained. The double layer capacitances of the modified electrodes are increased by about one order after surface-modification. The developed microchip is used to monitor the adhering behavior of a single HeLa cell by measuring its impedance spectra in real time. The measured impedance is analyzed and used to extract cellular electrical parameters, which demonstrated that the cell compresses the electrical double layer in the process of adherence and adheres onto the measuring electrodes after 4-5 hours.

  2. Influence of heart motion on cardiac output estimation by means of electrical impedance tomography: a case study.

    PubMed

    Proença, Martin; Braun, Fabian; Rapin, Michael; Solà, Josep; Adler, Andy; Grychtol, Bartłomiej; Bohm, Stephan H; Lemay, Mathieu; Thiran, Jean-Philippe

    2015-06-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technique that can measure cardiac-related intra-thoracic impedance changes. EIT-based cardiac output estimation relies on the assumption that the amplitude of the impedance change in the ventricular region is representative of stroke volume (SV). However, other factors such as heart motion can significantly affect this ventricular impedance change. In the present case study, a magnetic resonance imaging-based dynamic bio-impedance model fitting the morphology of a single male subject was built. Simulations were performed to evaluate the contribution of heart motion and its influence on EIT-based SV estimation. Myocardial deformation was found to be the main contributor to the ventricular impedance change (56%). However, motion-induced impedance changes showed a strong correlation (r = 0.978) with left ventricular volume. We explained this by the quasi-incompressibility of blood and myocardium. As a result, EIT achieved excellent accuracy in estimating a wide range of simulated SV values (error distribution of 0.57 ± 2.19 ml (1.02 ± 2.62%) and correlation of r = 0.996 after a two-point calibration was applied to convert impedance values to millilitres). As the model was based on one single subject, the strong correlation found between motion-induced changes and ventricular volume remains to be verified in larger datasets.

  3. Feasibility of Bioelectrical Impedance Spectroscopy Measurement before and after Thoracentesis

    PubMed Central

    Weyer, Sören; Pauly, Karolin; Napp, Andreas; Dreher, Michael; Leonhardt, Steffen; Marx, Nikolaus; Schauerte, Patrick; Mischke, Karl

    2015-01-01

    Background. Bioelectrical impedance spectroscopy is applied to measure changes in tissue composition. The aim of this study was to evaluate its feasibility in measuring the fluid shift after thoracentesis in patients with pleural effusion. Methods. 45 participants (21 with pleural effusion and 24 healthy subjects) were included. Bioelectrical impedance was analyzed for “Transthoracic,” “Foot to Foot,” “Foot to Hand,” and “Hand to Hand” vectors in low and high frequency domain before and after thoracentesis. Healthy subjects were measured at a single time point. Results. The mean volume of removed pleural effusion was 1169 ± 513 mL. The “Foot to Foot,” “Hand to Hand,” and “Foot to Hand” vector indicated a trend for increased bioelectrical impedance after thoracentesis. Values for the low frequency domain in the “Transthoracic” vector increased significantly (P < 0.001). A moderate correlation was observed between the amount of removed fluid and impedance change in the low frequency domain using the “Foot to Hand” vector (r = −0.7). Conclusion. Bioelectrical impedance changes in correlation with the thoracic fluid level. It was feasible to monitor significant fluid shifts and loss after thoracentesis in the “Transthoracic” vector by means of bioelectrical impedance spectroscopy. The trial is registered with Registration Numbers IRB EK206/11 and NCT01778270. PMID:25861647

  4. 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.

  5. 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

  6. What the electrical impedance can tell about the intrinsic properties of an electrodynamic shaker.

    PubMed

    Lütkenhöner, Bernd

    2017-01-01

    Small electrodynamic shakers are becoming increasingly popular for diagnostic investigations of the human vestibular system. More specifically, they are used as mechanical stimulators for eliciting a vestibular evoked myogenic potential (VEMP). However, it is largely unknown how shakers perform under typical measurement conditions, which considerably differ from the normal use of a shaker. Here, it is shown how the basic properties of a shaker can be determined without requiring special sensors such as accelerometers or force gauges. In essence, the mechanical parts of the shaker leave a signature in the electrical impedance, and an interpretation of this signature using a simple model allows for drawing conclusions about the properties of the shaker. The theory developed (which is quite general so that it is usable also in other contexts) is applied to experimental data obtained for the minishaker commonly used in VEMP measurements. It is shown that the experimental conditions substantially influence the properties of the shaker. Relevant factors are, in particular, the spatial orientation of the shaker (upright, horizontal or upside-down) and the static force acting on the table of the shaker (which in a real measurement corresponds to the force by which the shaker is pressed against the test person's head). These results underline the desirability of a proper standardization of VEMP measurements. Direct measurements of displacement and acceleration prove the consistency of the conclusions derived from the electrical impedance.

  7. What the electrical impedance can tell about the intrinsic properties of an electrodynamic shaker

    PubMed Central

    Lütkenhöner, Bernd

    2017-01-01

    Small electrodynamic shakers are becoming increasingly popular for diagnostic investigations of the human vestibular system. More specifically, they are used as mechanical stimulators for eliciting a vestibular evoked myogenic potential (VEMP). However, it is largely unknown how shakers perform under typical measurement conditions, which considerably differ from the normal use of a shaker. Here, it is shown how the basic properties of a shaker can be determined without requiring special sensors such as accelerometers or force gauges. In essence, the mechanical parts of the shaker leave a signature in the electrical impedance, and an interpretation of this signature using a simple model allows for drawing conclusions about the properties of the shaker. The theory developed (which is quite general so that it is usable also in other contexts) is applied to experimental data obtained for the minishaker commonly used in VEMP measurements. It is shown that the experimental conditions substantially influence the properties of the shaker. Relevant factors are, in particular, the spatial orientation of the shaker (upright, horizontal or upside-down) and the static force acting on the table of the shaker (which in a real measurement corresponds to the force by which the shaker is pressed against the test person’s head). These results underline the desirability of a proper standardization of VEMP measurements. Direct measurements of displacement and acceleration prove the consistency of the conclusions derived from the electrical impedance. PMID:28328999

  8. Measurement and modelling the sensitivity of tetrapolar transfer impedance measurements.

    PubMed

    Naydenova, E; Cavendish, S; Wilson, A J

    2016-10-01

    Finite element method (FEM) modelling of a small disk in a homogeneous saline medium showed that the sensitivity distribution for tetrapolar transfer impedance measurements was dependant on the ratio, σdisk/σsaline, and not absolute conductivity values. In addition, the amplitude of the negative sensitivity regions between the drive and receive electrodes decreased non-linearly with σdisk/σsaline for σdisk/σsaline < 1, eventually becoming zero. This non-linear behaviour determined the limit of the assumption of a small change in conductivity in Geselowitz's lead theorem with 0.5 <σdisk/σsaline <1.5 for the measurements reported. The modelling supported the design of a sensitivity measurement system using an insulating support and a metal disk in a saline filled tank. Measurements were shown to give good agreement with sensitivity predictions from Geselowitz's lead theorem. Replacing the homogeneous medium in the FEM model with layers of different conductivity parallel to the plane of the electrodes changed the sensitivity distribution when the thickness of the layers adjacent to the electrodes were less than ½ the electrode spacing. A layer of greater conductivity over a layer of lesser conductivity next to the electrodes gave a peak in the sensitivity distribution and extended regions of negative sensitivity further into the tissue.

  9. Tissue type determination by impedance measurement: A bipolar and monopolar comparison

    PubMed Central

    Sharp, Jack; Bouazza-Marouf, Kaddour; Noronha, Dorita; Gaur, Atul

    2017-01-01

    Background: In certain medical applications, it is necessary to be able to determine the position of a needle inside the body, specifically with regards to identifying certain tissue types. By measuring the electrical impedance of specific tissue types, it is possible to determine the type of tissue the tip of the needle (or probe) is at. Materials and Methods: Two methods have been investigated for electric impedance detection; bipolar and monopolar. Commercially available needle electrodes are of a monopolar type. Although many patents exist on the bipolar setups, these have not as yet been commercialized. This paper reports a comparison of monopolar and bipolar setups for tissue type determination. In vitro experiments were carried out on pork to compare this investigation with other investigations in this field. Results: The results show that both monopolar and bipolar setups are capable of determining tissue type. However, the bipolar setup showed slightly better results; the difference between the different soft tissue type impedances was greater compared to the monopolar method. Conclusion: Both monopolar and bipolar electrical impedance setups work very similarly in inhomogeneous volumes such as biological tissue. There is a clear potential for clinical applications with impedance-based needle guidance, with both the monopolar and bipolar setups. It is, however, worth noting that the bipolar setup is more versatile. PMID:28217047

  10. In situ impedance measurement of microwave atmospheric pressure plasma

    NASA Astrophysics Data System (ADS)

    Lee, S. T.; Nam, W. J.; Lee, J. K.; Yun, G. S.

    2017-04-01

    The impedance of atmospheric pressure argon plasma jets driven by microwave frequency is determined in situ by a novel ‘two frequency method’. In the conventional method of reflection coefficient ({{S}}11) measurement, the frequency of the driving microwave power is scanned, which inevitably affects the plasma characters and leads to uncertainty in the estimated plasma impedance. In our proposed method, the frequency-scanning signal additional to the driving power is used to measure {{S}}11 over a wide frequency range, which enables accurate determination of the plasma impedance based on an equivalent circuit model. The measured resistance and reactance of the plasma increase with the driving power in agreement with the transmission line theory. Based on this in situ measurement of the plasma impedance, the net power coupled to the plasma has been determined. The overall power efficiency remains approximately unchanged around 45% for different input power levels owing to the competing effects between the impedance mismatch and the volume change of the plasma.

  11. 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.

  12. Damage detection in plates using the electromechanical impedance technique based on decoupled measurements of piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Tinoco, Hector A.; Robledo-Callejas, Leonardo; Marulanda, Dairon J.; Serpa, Alberto L.

    2016-12-01

    Electromechanical impedance (EMI) technique plays an important role in the monitoring of structures with piezoelectric transducers (PT). According to the EMI technique, diagnosis and prognosis can be carried out to detect structural modifications in an operative state. However, to develop an efficient methodology for damage detection; damage metrics and patterns should be defined using indices to quantify changes in the signals. In this study, a new approach is proposed considering the electrical impedance (EI) of PT as an array of coupled electrical impedances. It means that when a PT is bonded to a structure, the EI is governed by an electrical circuit that is assumed to be parallel and composed by electrical contributions of both, the structure and the PT. In our perspective, each free PT presents unique mechanical characteristics and those differences may influence the measured electrical signals, therefore the electrical contributions generated by each piezo-transducer are taken into account. To evaluate the electrical decoupling, two methodologies of damage detection are proposed to identify and locate an induced damage. In these methodologies, the damage metrics are based on ellipses of Gaussian confidence. Four experimental tests were performed to evaluate the methodologies, applying two damage intensities. The results show that the partial process of identification of a damage type is a feasible and applicable procedure, moreover the proposed method was able to evidence the damage location..

  13. Analogies between the measurement of acoustic impedance via the reaction on the source method and the automatic microwave vector network analyzer technique

    NASA Astrophysics Data System (ADS)

    McLean, James; Sutton, Robert; Post, John

    2003-10-01

    One useful method of acoustic impedance measurement involves the measurement of the electrical impedance ``looking into'' the electrical port of a reciprocal electroacoustic transducer. This reaction on the source method greatly facilitates the measurement of acoustic impedance by borrowing highly refined techniques to measure electrical impedance. It is also well suited for in situ acoustic impedance measurements. In order to accurately determine acoustic impedance from the measured electrical impedance, the characteristics of the transducer must be accurately known, i.e., the characteristics of the transducer must be ``removed'' completely from the data. The measurement of acoustic impedance via the measurement of the reaction on the source is analogous to modern microwave measurements made with an automatic vector network analyzer. The action of the analyzer is described as de-embedding the desired data (such as acoustic impedance) from the raw data. Such measurements are fundamentally substitution measurements in that the transducer's characteristics are determined by measuring a set of reference standards. The reaction on the source method is extended to take advantage of improvements in microwave measurement techniques which allow calibration via imperfect standard loads. This removes one of the principal weaknesses of the method in that the requirement of high-quality reference standards is relaxed.

  14. 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.

  15. Effect of electrode impedance on spread of excitation and pitch perception using electrically coupled “dual-electrode” stimulation

    PubMed Central

    Hughes, Michelle L.; Baudhuin, Jacquelyn L.; Goehring, Jenny L.

    2014-01-01

    Objective In newer-generation Cochlear Ltd. cochlear implants, two adjacent electrodes can be electrically coupled to produce a single contact or “dual electrode” (DE). The goal of the present study was to evaluate whether relatively large impedance differences (>3.0 kOhms) between coupled electrodes affect the excitation pattern and pitch percepts produced by the DE. Design Fifteen electrode pairs in six recipients were tested. Neural spread-of-excitation (SOE) patterns and pitch perception were measured for adjacent physical electrodes (PEs) and the resulting DE to determine if the lower-impedance PE in the pair dominates the DE response pattern. Results were compared to a “normative sample” (impedance differences <3.0 kOhms) from two earlier studies. Results In general, SOE patterns for DEs more closely approximated those of the lower-impedance PE in each pair. The DE was more easily distinguished in pitch from the higher-impedance PE than the lower-impedance PE. The ECAP and perceptual results generally differed from those of the normative group. Conclusions Impedance differences between adjacent PEs should be considered if DE stimulation is implemented in future research studies or clinical coding strategies. PMID:25250960

  16. Impedance spectroscopy as an indicator for successful in vivo electric field mediated gene delivery in a murine model.

    PubMed

    Atkins, Reginald M; Fawcett, Timothy J; Gilbert, Richard; Hoff, Andrew M; Connolly, Richard; Brown, Douglas W; Llewellyn, Anthony J; Jaroszeski, Mark J

    2017-06-01

    In vivo gene electro transfer technology has been very successful both in animal models and in clinical trials over the past 20years. However, variable transfection efficiencies can produce inconsistent outcomes. This can be due to differences in tissue architecture and/or chemical composition which may effectively create unique biological environments from subject to subject that may respond differently to the identical electric pulses. This study investigates the integration of impedance spectroscopy into the gene electro transfer process to measure murine skin impedance spectra before, during (after pulse delivery), and after gene electro transfer pulse application to determine if changes in impedance correlate with reporter gene expression. Both post-treatment impedance spectra and gene expression were dependent upon the applied electric field strength. These results indicate that alterations in tissue impedance produced by the applied electric field represent an excellent parameter to predict degrees of transfection and gene expression. These results could ultimately be used to alter pulsing parameters in order to optimize delivery/expression.

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

    PubMed Central

    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 mm2, 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 μA. Each CR channel occupies an area of 0.21 mm2. The chip consumes between 530 μA and 690 μA 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. 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

  19. Real-time monitoring of flavivirus induced cytopathogenesis using cell electric impedance technology.

    PubMed

    Fang, Ying; Ye, Peifang; Wang, Xiaobo; Xu, Xiao; Reisen, William

    2011-05-01

    A real-time cell analysis (RTCA) system based on cell-substrate electric impedance technology was used to monitor cytopathic effects (CPE) in Vero cell cultures infected with West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) at infectious doses ranging from 10(1) to 10(6) plaque forming units (PFU) of virus. A kinetic parameter characterizing virus-induced CPE, CIT(50) or the time to 50% decrease in cell impedance, was inversely proportional to virus infectious dose. In WNV-infected cells, the onset and rate of CPE was earlier and faster than in SLEV-infected cells, which was consistent with viral cytolytic activity. A mathematical model simulating impedance-based CPE kinetic curves indicated that the replication rate of WNV was about 3 times faster than SLEV. The RTCA system also was used for quantifying the level of cell protection by specific neutralizing antibodies against WNV and SLEV. The onset of WNV or SLEV-induced CPE was delayed in the presence of specific anti-sera, and this delay in the CIT(50) was well correlated with the titer of the neutralizing antibody as measured independently by plaque reduction neutralization tests (PRNT). The RTCA system provided a high throughput and quantitative method for real-time monitoring viral growth in cell culture and its inhibition by neutralizing antibodies.

  20. A simple mathematical model for electric cell-substrate impedance sensing with extended applications.

    PubMed

    Xiao, Caide; Luong, John H T

    2010-03-15

    This paper presents a simple mathematical model to predict the impedance data acquired by electric cell-substrate impedance sensing (ECIS) at frequencies between 25 Hz and 60 kHz. With this model, the equivalent resistance (R) and capacitance (C) of biological samples adhered on gold surfaces could be more precisely measured at 4 kHz. ECIS applications were extended for real-time monitoring of living bacteria cultivated in Luria Bertani (LB) culture medium by two different approaches. In the former, we used a ferri/ferrocyanide redox couple in LB medium as an indicator for bacterial multiplication. Because the redox couple was toxic to some bacteria, we developed a second approach, in which l-cysteine self-assembled monolayers (SAM) on gold electrodes were used to detect living bacteria. The l-cysteine SAM could also be detected by ECIS. Unlike traditional impedance microbiological methods which need special culture media with low ions, our procedures significantly enhanced signal/noise ratios so bacteria could be detected in general purpose culture media. It was easy and convenient to obtain bacterial doubling times and evaluate the resistance of bacteria to antibiotics from ECIS spectra.

  1. 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

  2. Electrical Impedance Spectroscopy of Microchannel-Nanochannel Interface Devices

    NASA Astrophysics Data System (ADS)

    Schiffbauer, Jarrod; Park, Sinwook; Yossifon, Gilad

    2013-05-01

    We report experimental verification of the depression of the slope in the Warburg branch of the electrochemical impedance spectrum using a fabricated microchannel-nanochannel device. This was previously theoretically predicted to occur with increasing dc bias voltage as a result of nanochannel electro-osmotic flow and provides an example of the influence of net fluid flow on electrokinetic transport. The dominant influence of nanochannel polarization in the kHz range of the impedance response is also demonstrated experimentally. This latter effect may be significant in both fundamental electrokinetics of micronanochannel devices as well as in practical molecular sensing applications.

  3. Tissue characterization using electrical impedance spectroscopy data: a linear algebra approach.

    PubMed

    Laufer, Shlomi; Solomon, Stephen B; Rubinsky, Boris

    2012-06-01

    In this study, we use a new linear algebra manipulation on electrical impedance spectroscopy measurements to provide real-time information regarding the nature of the tissue surrounding the needle in minimal invasive procedures. Using a Comsol Multiphysics three-dimensional model, a phantom based on ex vivo animal tissue and in vivo animal data, we demonstrate how tissue inhomogeneity can be characterized without any previous knowledge of the electrical properties of the different tissues, except that they should not be linearly dependent on a certain frequency range. This method may have applications in needle biopsies, radiation seeds, or minimally invasive surgery and can reduce the number of computer tomography or magnetic resonance imaging images. We conclude by demonstrating how this mathematical approach can be useful in other applications.

  4. TOPICAL REVIEW: Electrical impedance tomography and Calderón's problem

    NASA Astrophysics Data System (ADS)

    Uhlmann, G.

    2009-12-01

    We survey mathematical developments in the inverse method of electrical impedance tomography which consists in determining the electrical properties of a medium by making voltage and current measurements at the boundary of the medium. In the mathematical literature, this is also known as Calderón's problem from Calderón's pioneer contribution (Calderón 1980 Seminar on Numerical Analysis and its Applications to Continuum Physics (Río de Janeiro, 1980) p 65 (Soc. Brasil. Mat.)). We concentrate this review around the topic of complex geometrical optics solutions that have led to many advances in the field. In the last section, we review some counterexamples to Calderón's problems that have attracted a lot of interest because of connections with cloaking and invisibility.

  5. Bunch Length and Impedance Measurements at SPEAR3

    SciTech Connect

    Corbett, W.J.; Cheng, W.X.; Fisher, A.S.; Huang, X.; /SLAC

    2011-11-02

    Streak camera measurements were made at SPEAR3 to characterize longitudinal coupling impedance. For the nominal optics, data was taken at three rf voltages and a single-bunch current range of 0-20mA. Both bunchcentroid phase shift and bunch lengthening were recorded to extract values for resistive and reactive impedance. An (R+L) and a Q=1 model were then back-substituted into the Haissinski equation and compared with raw profile data. In the short bunch (low-{alpha}) mode, distribution 'bursting' was observed.

  6. The development of the miniaturized waveform receiver with the function measuring Antenna Impedance in space plasmas

    NASA Astrophysics Data System (ADS)

    Ishii, H.; Kojima, H.; Fukuhara, H.; Okada, S.; Yamakawa, H.

    2012-04-01

    Plasma wave is one of the most essential physical quantities in the solar terrestrial physics. The role of plasma wave receiver onboard satellites is to detect plasma waves in space with a good signal to noise ratio. There are two types of plasma wave receivers, the sweep frequency analyzer and the waveform capture. While the sweep frequency analyzer provides plasma wave spectra, the waveform capture obtains waveforms with phase information that is significant in studying nonlinear phenomena. Antenna sensors to observe electric fields of the plasma waves show different features in plasmas from in vacuum. The antenna impedances have specific characteristics in the frequency domain because of the dispersion of plasmas. These antenna impedances are expressed with complex number. We need to know not only the antenna impedances but also the transfer functions of plasma wave receiver's circuits in order to calibrate observed waveforms precisely. The impedances of the electric field antennas are affected by a state of surrounding plasmas. Since satellites run through various regions with different plasma parameters, we precisely should measure the antenna impedances onboard spacecraft. On the contrary, we can obtain the plasma density and by measuring the antenna impedances. Several formulas of the antenna impedance measurement system were proposed. A synchronous detection method is used on the BepiColombo Mercury Magnetospheric Orbiter (MMO), which will be launched in 2014. The digital data are stored in the onboard memory. They are read out and converted to the analog waveforms by D/A converter. They are fed into the input of the preamplifiers of antenna sensors through a resistor. We can calculate a transfer function of the circuit by applying the synchronous detection method to the output waveform from waveform receivers and digital data as a signal source. The size of this system is same as an A5 board. In recent years, Application Specific Integrated Circuit (ASIC

  7. High Dynamic Range Complex Impedance Measurement System for Petrophysical Usage

    NASA Astrophysics Data System (ADS)

    Chen, R.; He, X.; Yao, H.; Tan, S.; Shi, H.; Shen, R.; Yan, C.; Zeng, P.; He, L.; Qiao, N.; Xi, F.; Zhang, H.; Xie, J.

    2015-12-01

    Spectral induced polarization method (SIP) or complex resistivity method is increasing its application in metalliferous ore exploration, hydrocarbon exploration, underground water exploration, monitoring of environment pollution, and the evaluation of environment remediation. And the measurement of complex resistivity or complex impedance of rock/ore sample and polluted water plays a fundamental role in improving the application effect of SIP and the application scope of SIP. However, current instruments can't guaranty the accuracy of measurement when the resistance of sample is less than 10Ω or great than 100kΩ. A lot of samples, such as liquid, polluted sea water, igneous rock, limestone, and sandstone, can't be measured with reliable complex resistivity result. Therefore, this problem projects a shadow in the basic research and application research of SIP. We design a high precision measurement system from the study of measurement principle, sample holder, and measurement instrument. We design input buffers in a single board. We adopt operation amplifier AD549 in this system because of its ultra-high input impedance and ultra-low current noise. This buffer is good in acquiring potential signal across high impedance sample. By analyzing the sources of measurement error and errors generated by the measurement system, we propose a correction method to remove the error in order to achieve high quality complex impedance measurement for rock and ore samples. This measurement system can improve the measurement range of the complex impedance to 0.1 Ω ~ 10 GΩ with amplitude error less than 0.1% and phase error less than 0.1mrad when frequency ranges as 0.01 Hz ~ 1 kHz. We tested our system on resistors with resistance as 0.1Ω ~ 10 GΩ in frequency range as 1 Hz ~ 1000 Hz, and the measurement error is less than 0.1 mrad. We also compared the result with LCR bridge and SCIP, we can find that the bridge's measuring range only reaches 100 MΩ, SCIP's measuring range

  8. Rapid, electrical impedance detection of bacterial pathogens using immobilized antimicrobial peptides.

    PubMed

    Lillehoj, Peter B; Kaplan, Christopher W; He, Jian; Shi, Wenyuan; Ho, Chih-Ming

    2014-02-01

    The detection of bacterial pathogens plays an important role in many biomedical applications, including clinical diagnostics, food and water safety, and biosecurity. Most current bacterial detection technologies, however, are unsuitable for use in resource-limited settings where the highest disease burdens often exist. Thus, there is an urgent need to develop portable, user-friendly biosensors capable of rapid detection of multiple pathogens in situ. We report a microfluidic chip for multiplexed detection of bacterial cells that uses antimicrobial peptides (AMPs) with species-specific targeting and binding capabilities. The AMPs are immobilized onto an electrical impedance microsensor array and serve as biorecognition elements for bacterial cell detection. Characterization of peptide immobilization on the sensors revealed robust surface binding via cysteine-gold interactions and vertical alignment relative to the sensor surface. Samples containing Streptococcus mutans and Pseudomonas aeruginosa were loaded in the chip, and both microorganisms were detected at minimum concentrations of 10⁵ cfu/mL within 25 min. Measurements performed in a variety of solutions revealed that high-conductivity solutions produced the largest impedance values. By integrating a highly specific bacterial cell capture scheme with rapid electrical detection, this device demonstrates great potential as a next-generation, point-of-care diagnostic platform for the detection of disease-causing pathogenic agents.

  9. 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.

  10. 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

  11. Effects of steroids and lubricants on electrical impedance and tissue response following cochlear implantation.

    PubMed

    Huang, Christie Qi; Tykocinski, Michael; Stathopoulos, Dimitra; Cowan, Robert

    2007-09-01

    The present study examined the effects of steroids and lubricants on electrical impedance and tissue response following cochlear implantation in animal models. Guinea pigs were implanted following either no treatment, or intrascalar injection with dexamethasone, triamcinolone, sodium hyaluronate or saline. Cats were implanted following either no treatment, or intrascalar injection with dexamethasone, triamcinolone or a mixture of triamcinolone with sodium hyaluronate. In guinea pigs, impedance changes and intracochlear tissue response were less for the hyaluronate and saline groups. In cats, impedance in the dexamethasone group increased similar to non-treated cats. Impedance of triamcinolone treated cats remained low for about two months after implantation, before increasing to levels similar to the other groups. Significant fibrous tissue growth was observed histologically. The results of the present study indicate that a single intracochlear application of hyaluronate or triamcinolone may postpone, but will ultimately not prevent the rise in impedance following cochlear implantation.

  12. Assessment of Optimized Electrode Configuration for Electrical Impedance Myography Using Genetic Algorithm via Finite Element Model

    PubMed Central

    Baidya, Somen

    2016-01-01

    Electrical Impedance Myography (EIM) is a noninvasive neurophysiologic technique to diagnose muscle health. Besides muscle properties, the EIM measurements vary significantly with the change of some other anatomic and nonanatomic factors such as skin fat thickness, shape and thickness of muscle, and electrode size and spacing due to its noninvasive nature of measurement. In this study, genetic algorithm was applied along with finite element model of EIM as an optimization tool in order to figure out an optimized EIM electrode setup, which is less affected by these factors, specifically muscle thickness variation, but does not compromise EIM's ability to detect muscle diseases. The results obtained suggest that a particular arrangement of electrodes and minimization of electrode surface area to its practical limit can overcome the effect of undesired factors on EIM parameters to a larger extent. PMID:27843937

  13. Determination of Complex Microcalorimeter Parameters with Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Saab, T.; Bandler, S. R.; Chervenak, J.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C. A.; Lindeman, M. A.; Porter, F. S.; Sadleir, J.

    2005-01-01

    The proper understanding and modeling of a microcalorimeter s response requires the accurate knowledge of a handful of parameters, such as C, G, alpha, . . . . While a few of these, such 8s the normal state resistance and the total thermal conductance to the heat bath (G) are directly determined from the DC IV characteristics, some others, notoriously the heat capacity (C) and alpha, appear in degenerate combinations in most measurable quantities. The case of a complex microcalorimeter, i.e. one in which the absorber s heat capacity is connected by a finite thermal impedance to the sensor, and subsequently by another thermal impedance to the heat bath, results in an added ambiguity in the determination of the individual C's and G's. In general, the dependence of the microcalorimeter s complex impedance on these parameters varies with frequency. This variation allows us to determine the individual parameters by fitting the prediction of the microcalorimeter model to the impedance data. We describe in this paper our efforts at characterizing the Goddard X-ray microcalorimeters. Using the parameters determined with this method we them compare the pulse shape and noise spectra predicted by the microcalorimeter model to data taken with the same devices.

  14. Contactless impedance sensors and their application to flow measurements.

    PubMed

    Opekar, František; Tůma, Petr; Stulík, Karel

    2013-02-27

    The paper provides a critical discussion of the present state of the theory of high-frequency impedance sensors (now mostly called contactless impedance or conductivity sensors), the principal approaches employed in designing impedance flow-through cells and their operational parameters. In addition to characterization of traditional types of impedance sensors, the article is concerned with the use of less common sensors, such as cells with wire electrodes or planar cells. There is a detailed discussion of the effect of the individual operational parameters (width and shape of the electrodes, detection gap, frequency and amplitude of the input signal) on the response of the detector. The most important problems to be resolved in coupling these devices with flow-through measurements in the liquid phase are also discussed. Examples are given of cell designs for continuous flow and flow-injection analyses and of detection systems for miniaturized liquid chromatography and capillary electrophoresis. New directions for the use of these sensors in molecular biology and chemical reactors and some directions for future development are outlined.

  15. 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.

  16. Linearized image reconstruction method for ultrasound modulated electrical impedance tomography based on power density distribution

    NASA Astrophysics Data System (ADS)

    Song, Xizi; Xu, Yanbin; Dong, Feng

    2017-04-01

    Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results.

  17. A new non-iterative reconstruction method for the electrical impedance tomography problem

    NASA Astrophysics Data System (ADS)

    Ferreira, A. D.; Novotny, A. A.

    2017-03-01

    The electrical impedance tomography (EIT) problem consists in determining the distribution of the electrical conductivity of a medium subject to a set of current fluxes, from measurements of the corresponding electrical potentials on its boundary. EIT is probably the most studied inverse problem since the fundamental works by Calderón from the 1980s. It has many relevant applications in medicine (detection of tumors), geophysics (localization of mineral deposits) and engineering (detection of corrosion in structures). In this work, we are interested in reconstructing a number of anomalies with different electrical conductivity from the background. Since the EIT problem is written in the form of an overdetermined boundary value problem, the idea is to rewrite it as a topology optimization problem. In particular, a shape functional measuring the misfit between the boundary measurements and the electrical potentials obtained from the model is minimized with respect to a set of ball-shaped anomalies by using the concept of topological derivatives. It means that the objective functional is expanded and then truncated up to the second order term, leading to a quadratic and strictly convex form with respect to the parameters under consideration. Thus, a trivial optimization step leads to a non-iterative second order reconstruction algorithm. As a result, the reconstruction process becomes very robust with respect to noisy data and independent of any initial guess. Finally, in order to show the effectiveness of the devised reconstruction algorithm, some numerical experiments into two spatial dimensions are presented, taking into account total and partial boundary measurements.

  18. Electrode-Skin contact impedance: In vivo measurements on an ovine model

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The problem of electrical impedance between the skin and the electrode is an on-going challenge in bio-electronics. This is particularly true in the case of Electrical Impedance Tomography (EIT), which uses a large number of skin-contact electrodes and is very sensitive to noise. In the present article, contact impedance is measured and compared for a range of electrodes placed on the thorax of an ovine model. The study has been approved by the Westmead Hospital Animal Ethics Committee. The electrode models that were employed in the research are Ag/AgCl electrodes (E1), commonly used for ECG and EIT measurements in both humans and animal models, stainless steel crocodile clips (E2), typically used on animal models, and novel multi-point dry electrodes in two modifications: bronze plated (E3) and nickel plated (E4). Further, since the contact impedance is mostly attributed to the acellular outer layer of the skin, in our experiment, we attempted to study the effect of this layer by comparing the results when the skin is intact and when electrodes are introduced underneath the skin through small cuts. This boundary effect was assessed by comparison of measurements obtained during E2 skin surface contact, and sub-cutaneous contact (E5). Twelve gauge intradermal needles were also tested as an electrode (E6). The full impedance spectrum, from 500 Hz to 300 kHz, was recorded, analysed and compared. As expected, the contact impedance in the more invasive cases, i.e the electrodes under the skin, is significantly lower than in the non-invasive cases. At the frequency of 50 kHz which is commonly used in lung EIT acquisition, electrodes E3, E4 and E6 demonstrated contact impedance of less than 200 Ω, compared to more than 400 Ω measured for electrodes E1, E2 and E5. In conclusion, the novel multipoint electrodes proved to be best suited for EIT purposes, because they are non-invasive and have lower contact impedance than Ag/AgCl and crocodile clips, in both invasive and

  19. Impedance of Polymer-Dispersed Liquid Crystals with Carbon Nanofibers in Weak Electric Fields

    NASA Astrophysics Data System (ADS)

    Zhdanov, K. R.; Romanenko, A. I.; Zharkova, G. M.; Podyacheva, O. Yu.

    2016-11-01

    Impedance of polymer-dispersed liquid crystals modified by carbon nanofibers is studied in fields lower than the threshold field of the director reorientation of a liquid crystal. It is shown that the real and imaginary parts of the impedance obey to the relationship (Zre - X0)2 + (Zim - Y0)2 = R 0 2 , where X0, Y0, and R0 are the fitting parameters depending on the frequency of the exciting electric field.

  20. Impedance spectroscopy applied to the fast wounding dynamics of an electrical wound-healing assay in mammalian cells

    NASA Astrophysics Data System (ADS)

    Bellotti, Mariela I.; Giana, Fabián E.; Bonetto, Fabián J.

    2015-08-01

    Electrical wound-healing assays are often used as a means to study in vitro cell migration and proliferation. In such analysis, a cell monolayer that sits on a small electrode is electrically wounded and its spectral impedance is then continuously measured in order to monitor the healing process. The relatively slow dynamics of the cell healing have been extensively studied, while those of the much faster wounding phase have not yet been investigated. An analysis of the electrical properties of a particular cell type during this phase could give extra information about the changes in the cell membrane due to the application of the wounding current, and could also be useful to optimize the wounding regime for different cell types. The main issue when trying to register information about these dynamics is that the traditional measurement scheme employed in typical wound-healing assays doesn’t allow the simultaneous application of the wounding signal and measurement of the system’s impedance. In this paper, we overcome this limitation by implementing a measurement strategy consisting of cycles of fast alternating low- and high-voltage signals applied on electrodes covered with mammalian cells. This approach is capable of registering the fast impedance changes during the transient regime corresponding to the cell wounding process. Furthermore, these quasi-simultaneous high- and low-voltage measurements can be compared in order to obtain an empirical correlation between both quantities.

  1. Automated, Multiplexed Electrical Impedance Spectroscopy Platform for Continuous Monitoring of Microtissue Spheroids.

    PubMed

    Bürgel, Sebastian C; Diener, Laurin; Frey, Olivier; Kim, Jin-Young; Hierlemann, Andreas

    2016-11-15

    Microtissue spheroids in microfluidic devices are increasingly used to establish novel in vitro organ models of the human body. As the spheroids are comparably sizable, it is difficult to monitor larger numbers of them by optical means. Therefore, electrical impedance spectroscopy (EIS) emerges as a viable alternative to probing spheroid properties. Current spheroid EIS systems are, however, not suitable for investigating multiple spheroids in parallel over extended time in an automated fashion. Here we address this issue by presenting an automated, multiplexed EIS (AMEIS) platform for impedance analysis in a microfluidic setting. The system was used to continuously monitor the effect of the anticancer drug fluorouracil (5-FU) on HCT116 cancer spheroids. Simultaneous EIS monitoring of up to 15 spheroids was performed in parallel over 4 days at a temporal resolution of 2 min without any need for pumps. The measurements were continuous in nature, and the setup was kept in a standard incubator under controlled conditions during the measurements. A baseline normalization method to improve robustness and to reduce the influence of slow changes in the medium conductivity on the spheroid EIS readings has been developed and validated by experiments and means of a finite-element model. The same method and platform was then used for online monitoring of cardiac spheroids. The beating frequency of each cardiac spheroid could be read out in a completely automated fashion. The developed system constitutes a promising method for simultaneously evaluating drug impact and/or toxic effects on multiple microtissue spheroids.

  2. Numerical analysis on effective electric field penetration depth for interdigital impedance sensor

    NASA Astrophysics Data System (ADS)

    Kim, Chon-ung; Li, Guofeng; Li, Jie; Jong, Hakchol; Ro, Cholwu; Song, Yunho; Pak, Gilhung; Im, Songil

    2013-03-01

    Interdigital (finger-like) electrodes are widely used for electrical impedance and capacitance tomography of composite dielectric materials and complex insulating structures. Because of their advantages, they are now effectively introduced as capacitance sensors into a variety of industrial branches, agriculture, medical science, biological engineering, military branches, etc. In order to effectively apply the so-called interdigital impedance sensors in practice, of great importance is to optimize the sensor design parameters such as the electric field penetration depth, signal strength and so on. The general design principles of the interdigital capacitance sensor have been discussed for a long time by many researchers. However, there is no consensus on the definition of the effective electric field penetration depth of interdigital electrode. This paper discusses how to determine the effective electric field penetration depth of interdigital sensor on the basis of the refractive principle of electric field intensity and the FEM analyses of electric field distribution and capacitance for the sensor model.

  3. Unfolding plasma density from cylindrical monopole impedance measurements in ionosphere

    NASA Astrophysics Data System (ADS)

    Kiraga, A.

    2003-04-01

    Several common problems occur in measurement techniques and interpretation of plasma natural emissions and impedance data. Antenna characteristics are of prime importance in equivalent circuit analysis. Spacecraft - plasma interaction contributes to variability of equivalent circuit impedances and e.m.f. components and imposes constrains on usefulness of experimental data. In order to have independent, built in estimate of local plasma frequency and to get deeper insight into properties of equivalent circuit for wave diagnostics, impedance measurement was integrated with radio receivers on the ACTIVE, APEX and CORONAS satellites. Impedance measurements of 7.5m long monopole were performed in frequency range .1-10MHz with the frequency step of 50kHz, in voltage divider configuration. Due to high inclination of 82.5deg and altitude range of 500-3000km, data from very different plasmas were collected. Data can be split into quasi normal, disturbed and very disturbed measurements. Equivalent circuit structure evolved in attempt to match even very disturbed measurements. For quasi normal measurements, satisfactory matching is obtained with computed gyrofrequency fc and fitted plasma frequency fn, stray capacitance Cs and capacitance Cv of phenomenological vacuum sheath. With formulas for monopole impedance in cold magnetoplasma, two basic pectral structures are explained. For sufficiently magnetized plasma (roughly fn/fc<2 if Cs=20pF), circuit parallel resonance frequency Fr falls into upper hybrid band (max(fn,fc),fu), resonance amplitude is reduced by high antenna resistance and horn like absolute maximum points fu. For values of fn/fc ratio, greater then critical, Fr is less than fn and broad absolute maximum at Fr follows from low antenna resistance. Further increase of fn/fc results in increasing lag of Fr behind fn. Critical ratio fn/fc increases with decreasing stray capacitance Cs. It follows from data analysis that stray capacitance may change in flight, at

  4. 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

  5. Biomedical engineering meets acupuncture - development of a miniaturized 48-channel skin impedance measurement system for needle and laser acupuncture

    PubMed Central

    2010-01-01

    Background Due to controversially discussed results in scientific literature concerning changes of electrical skin impedance before and during acupuncture a new measurement system has been developed. Methods The prototype measures and analyzes the electrical skin impedance computer-based and simultaneously in 48 channels within a 2.5×3.5 cm matrix. Preliminary measurements in one person were performed using metal needle and violet laser (405 nm) acupuncture at the acupoint Kongzui (LU6). The new system is an improvement on devices previously developed by other researchers for this purpose. Results Skin impedance in the immediate surroundings of the acupoint was lowered reproducibly following needle stimulation and also violet laser stimulation. Conclusions A new instrumentation for skin impedance measurements is presented. The following hypotheses suggested by our results will have to be tested in further studies: Needle acupuncture causes significant, specific local changes of electrical skin impedance parameters. Optical stimulation (violet laser) at an acupoint causes direct electrical biosignal changes. PMID:21092296

  6. Cryogenic calibration setup for broadband complex impedance measurements

    NASA Astrophysics Data System (ADS)

    Diener, P.; Couëdo, F.; Marrache-Kikuchi, C.; Aprili, M.; Gabelli, J.

    2014-08-01

    Reflection measurements give access to the complex impedance of a material on a wide frequency range. This is of interest to study the dynamical properties of various materials, for instance disordered superconductors. However reflection measurements made at cryogenic temperature suffer from the difficulty to reliably subtract the circuit contribution. Here we report on the design and first tests of a setup able to precisely calibrate in situ the sample reflection, at 4.2 K and up to 2 GHz, by switching and measuring, during the same cool down, the sample and three calibration standards.

  7. Hydrodynamic and electrical considerations in the design of a four-electrode impedance-based microfluidic device.

    PubMed

    Justin, Gusphyl; Nasir, Mansoor; Ligler, Frances S

    2011-05-01

    A four-electrode impedance-based microfluidic device has been designed with tunable sensitivity for future applications to the detection of pathogens and functionalized microparticles specifically bound to molecular recognition molecules on the surface of a microfluidic channel. In order to achieve tunable sensitivity, hydrodynamic focusing was employed to confine the electric current by simultaneous introduction of two fluids (high- and low-conductivity solutions) into a microchannel at variable flow-rate ratios. By increasing the volumetric flow rate of the low-conductivity solution (sheath fluid) relative to the high-conductivity solution (sample fluid), increased focusing of the high-conductivity solution over four coplanar electrodes was achieved, thereby confining the current during impedance interrogation. The hydrodynamic and electrical properties of the device were analyzed for optimization and to resolve issues that would impact sensitivity and reproducibility in subsequent biosensor applications. These include variability in the relative flow rates of the sheath and sample fluids, changes in microchannel dimensions, and ionic concentration of the sample fluid. A comparative analysis of impedance measurements using four-electrode versus two-electrode configurations for impedance measurements also highlighted the advantages of using four electrodes for portable sensor applications.

  8. 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

  9. Compensation for geometric modeling errors by positioning of electrodes in electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Hyvönen, N.; Majander, H.; Staboulis, S.

    2017-03-01

    Electrical impedance tomography aims at reconstructing the conductivity inside a physical body from boundary measurements of current and voltage at a finite number of contact electrodes. In many practical applications, the shape of the imaged object is subject to considerable uncertainties that render reconstructing the internal conductivity impossible if they are not taken into account. This work numerically demonstrates that one can compensate for inaccurate modeling of the object boundary in two spatial dimensions by finding compatible locations and sizes for the electrodes as a part of a reconstruction algorithm. The numerical studies, which are based on both simulated and experimental data, are complemented by proving that the employed complete electrode model is approximately conformally invariant, which suggests that the obtained reconstructions in mismodeled domains reflect conformal images of the true targets. The numerical experiments also confirm that a similar approach does not, in general, lead to a functional algorithm in three dimensions.

  10. Circuit modeling of the electrical impedance: part III. Disuse following bone fracture.

    PubMed

    Shiffman, C A

    2013-05-01

    Multifrequency measurements of the electrical impedance of muscle have been extended to the study of disuse following bone fracture, and analyzed using the five-element circuit model used earlier in the study of the effects of disease. Eighteen subjects recovering from simple fractures on upper or lower limbs were examined (ten males, eight females, aged 18-66). Muscles on uninjured contralateral limbs were used as comparison standards, and results are presented in terms of the ratios p(injured)/p(uninjured), where p stands for the circuit parameter r1, r2, r3, 1/c1 or 1/c2. These are strikingly similar to the diseased-to-healthy ratios for patients with neuromuscular disease, reported in part I of this series. In particular, r1 is virtually unaffected and the ratios for r2, r3, 1/c1 and 1/c2 can be as large as in serious disease. Furthermore, the same pattern of relationships between the parameters is found, suggesting that there is a common underlying mechanism for the impedance changes. Atrophy and fibrosis are examined as candidates for that mechanism, but it is argued that their effects are too small to explain the observed changes. Fundamental considerations aside, the sensitivity, reproducibility and technical simplicity of the technique recommend its use for in-flight assessments of muscles during orbital or interplanetary missions.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

  12. 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

  13. A Versatile and Reproducible Multi-Frequency Electrical Impedance Tomography System

    PubMed Central

    Avery, James; Dowrick, Thomas; Faulkner, Mayo; Goren, Nir; Holder, David

    2017-01-01

    A highly versatile Electrical Impedance Tomography (EIT) system, nicknamed the ScouseTom, has been developed. The system allows control over current amplitude, frequency, number of electrodes, injection protocol and data processing. Current is injected using a Keithley 6221 current source, and voltages are recorded with a 24-bit EEG system with minimum bandwidth of 3.2 kHz. Custom PCBs interface with a PC to control the measurement process, electrode addressing and triggering of external stimuli. The performance of the system was characterised using resistor phantoms to represent human scalp recordings, with an SNR of 77.5 dB, stable across a four hour recording and 20 Hz to 20 kHz. In studies of both haeomorrhage using scalp electrodes, and evoked activity using epicortical electrode mats in rats, it was possible to reconstruct images matching established literature at known areas of onset. Data collected using scalp electrode in humans matched known tissue impedance spectra and was stable over frequency. The experimental procedure is software controlled and is readily adaptable to new paradigms. Where possible, commercial or open-source components were used, to minimise the complexity in reproduction. The hardware designs and software for the system have been released under an open source licence, encouraging contributions and allowing for rapid replication. PMID:28146122

  14. A Versatile and Reproducible Multi-Frequency Electrical Impedance Tomography System.

    PubMed

    Avery, James; Dowrick, Thomas; Faulkner, Mayo; Goren, Nir; Holder, David

    2017-01-31

    A highly versatile Electrical Impedance Tomography (EIT) system, nicknamed the ScouseTom, has been developed. The system allows control over current amplitude, frequency, number of electrodes, injection protocol and data processing. Current is injected using a Keithley 6221 current source, and voltages are recorded with a 24-bit EEG system with minimum bandwidth of 3.2 kHz. Custom PCBs interface with a PC to control the measurement process, electrode addressing and triggering of external stimuli. The performance of the system was characterised using resistor phantoms to represent human scalp recordings, with an SNR of 77.5 dB, stable across a four hour recording and 20 Hz to 20 kHz. In studies of both haeomorrhage using scalp electrodes, and evoked activity using epicortical electrode mats in rats, it was possible to reconstruct images matching established literature at known areas of onset. Data collected using scalp electrode in humans matched known tissue impedance spectra and was stable over frequency. The experimental procedure is software controlled and is readily adaptable to new paradigms. Where possible, commercial or open-source components were used, to minimise the complexity in reproduction. The hardware designs and software for the system have been released under an open source licence, encouraging contributions and allowing for rapid replication.

  15. Study of Paclitaxel-Treated HeLa Cells by Differential Electrical Impedance Flow Cytometry

    PubMed Central

    Kirkegaard, Julie; Clausen, Casper Hyttel; Rodriguez-Trujillo, Romen; Svendsen, Winnie Edith

    2014-01-01

    This work describes the electrical investigation of paclitaxel-treated HeLa cells using a custom-made microfluidic biosensor for whole cell analysis in continuous flow. We apply the method of differential electrical impedance spectroscopy to treated HeLa cells in order to elucidate the changes in electrical properties compared with non-treated cells. We found that our microfluidic system was able to distinguish between treated and non-treated cells. Furthermore, we utilize a model for electrical impedance spectroscopy in order to perform a theoretical study to clarify our results. This study focuses on investigating the changes in the electrical properties of the cell membrane caused by the effect of paclitaxel. We observe good agreement between the model and the obtained results. This establishes the proof-of-concept for the application in cell drug therapy. PMID:25587422

  16. An image reconstruction framework based on boundary voltages for ultrasound modulated electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Song, Xizi; Xu, Yanbin; Dong, Feng

    2016-11-01

    A new image reconstruction framework based on boundary voltages is presented for ultrasound modulated electrical impedance tomography (UMEIT). Combining the electric and acoustic modalities, UMEIT reconstructs the conductivity distribution with more measurements with position information. The proposed image reconstruction framework begins with approximately constructing the sensitivity matrix of the imaging object with inclusion. Then the conductivity is recovered from the boundary voltages of the imaging object. To solve the nonlinear inverse problem, an optimization method is adopted and the iterative method is tested. Compared with that for electrical resistance tomography (ERT), the newly constructed sensitivity matrix is more sensitive to the inclusion, even in the center of the imaging object, and it contains more effective information about the inclusions. Finally, image reconstruction is carried out by the conjugate gradient algorithm, and results show that reconstructed images with higher quality can be obtained for UMEIT with a faster convergence rate. Both theory and image reconstruction results validate the feasibility of the proposed framework for UMEIT and confirm that UMEIT is a potential imaging technique.

  17. Harmonic decomposition in PDE-based denoising technique for magnetic resonance electrical impedance tomography.

    PubMed

    Lee, Byung Il; Lee, Suk-Ho; Kim, Tae-Seong; Kwon, Ohin; Woo, Eung Je; Seo, Jin Keun

    2005-11-01

    Recent progress in magnetic resonance electrical impedance tomography (MREIT) research via simulation and biological tissue phantom studies have shown that conductivity images with higher spatial resolution and accuracy are achievable. In order to apply MREIT to human subjects, one of the important remaining problems to be solved is to reduce the amount of the injection current such that it meets the electrical safety regulations. However, by limiting the amount of the injection current according to the safety regulations, the measured MR data such as the z-component of magnetic flux density Bz in MREIT tend to have low SNR and get usually degraded in their accuracy due to the nonideal data acquisition system of an MR scanner. Furthermore, numerical differentiations of the measured Bz required by the conductivity image reconstruction algorithms tend to further deteriorate the quality and accuracy of the reconstructed conductivity images. In this paper, we propose a denoising technique that incorporates a harmonic decomposition. The harmonic decomposition is especially suitable for MREIT due to the physical characteristics of Bz. It effectively removes systematic and random noises, while preserving important key features in the MR measurements, so that improved conductivity images can be obtained. The simulation and experimental results demonstrate that the proposed denoising technique is effective for MREIT, producing significantly improved quality of conductivity images. The denoising technique will be a valuable tool in MREIT to reduce the amount of the injection current when it is combined with an improved MREIT pulse sequence.

  18. Study of surfactant-skin interactions by skin impedance measurements.

    PubMed

    Lu, Guojin; Moore, David J

    2012-02-01

    The stratum corneum (SC) plays a very critical physiological role as skin barrier in regulating water loss through the skin and protects the body from a wide range of physical and chemical exogenous insults. Surfactant-containing formulations can induce skin damage and irritation owing to surfactant absorption and penetration. It is generally accepted that reduction in skin barrier properties occurs only after surfactants have penetrated/permeated into the skin barrier. To mitigate the harshness of surfactant-based cleansing products, penetration/permeation of surfactants should be reduced. Skin impedance measurements have been taken in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, temperature and pH on skin barrier integrity. These skin impedance results demonstrate excellent correlation with other published methods for assessing skin damage and irritation from different surfactant chemistry, concentration, pH, time of exposure and temperature. This study demonstrates that skin impedance can be utilized as a routine approach to screen surfactant-containing formulations for their propensity to compromise the skin barrier and hence likely lead to skin irritation.

  19. 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.

  20. Generation of optimum pseudorandom signals for respiratory impedance measurements.

    PubMed

    Daróczy, B; Hantos, Z

    1990-02-01

    Spontaneous breathing may impair the reliability of forced oscillatory impedance estimates at low frequencies, especially when the oscillatory power is distributed among many frequency values. Since the amplitude of the external forcing is limited to avoid non-linearities, it is suggested that the total energy of a composite electrical signal driving the loudspeaker be maximized at a given amplitude by finding the optimum phase relationships of the signal components, and that the low-frequency components increase in energy at the expense of the less disturbed high-frequency region. In healthy children and adults and in obstructed patients, the coherences and the coefficients of variation of the respiratory system impedance (Zrs) at 2 and 3 Hz were studied in the case of three test signals of 2-15 Hz bandwidth. Signals T1 and T2 had a flat power spectrum, whereas the components of T3 decreased sharply between 2 and 5 Hz; T1 was generated by simple random selection of phase angles, while optimization for maximum energy was done for T2 and T3. Optimization alone (T2) increased the reliability of the Zrs estimates at all frequencies, whereas enhancement of the low-frequency power (T3) resulted in a radical improvement of the estimates at 2 and 3 Hz, without loss in reliability at higher frequencies.

  1. Supplementary pathway for vitality of wounds and wound age estimation in bruises using the electric impedance spectroscopy technique.

    PubMed

    Mao, Shiwei; Fu, Feng; Dong, Xiuzhen; Wang, Zhenyuan

    2011-07-01

    Determination of wound vitality and estimation of wound age are central issues in daily forensic practice. The objective of this study was to develop a new and rapid method for determining wound vitality and estimating wound age in bruises using electric impedance spectroscopy. Forty Sprague-Dawley rats (140-170 g) were divided into five groups: group 1 (n=8): controls, group 2 (n=8): postmortem bruises, group 3 (n=8): bruises 1 h before death, group 4 (n=8): bruises 3 h before death, group 5 (n=8): bruises 6 h before death. Measurements of the right gluteus maximus muscle were taken at 6, 24, and 48 h after the rats were sacrificed by cervical dislocation. The results from this study indicate that electric impedance spectroscopy is clearly sensitive enough to differentiate between vital and postmortem wound infliction and to determine the survival time after the infliction of an injury.

  2. Time course of electrical impedance during red blood cell aggregation in a glass tube: comparison with light transmittance.

    PubMed

    Baskurt, Oguz K; Uyuklu, Mehmet; Meiselman, Herbert J

    2010-04-01

    Red blood cells (RBC) in normal human blood undergo reversible aggregation at low flow or stasis. The extent and kinetics of this phenomenon have been studied using various optical and electrical methods, yet results using such methods are not always in concordance. This study employed a horizontal glass tube in which blood flow could be established, then abruptly stopped. Normal blood and RBC suspensions with enhanced or decreased aggregation were studied. Light transmittance (LT) and electrical impedance at 100 kHz were recorded during high-shear flow and for 120 s after flow was abruptly stopped during which RBC aggregation occurs. Capacitance values were also obtained based on the imaginary part of impedance data and recorded. Various aggregation parameters were calculated, using the time course of LT, impedance, and capacitance, then compared with each other and with results from laboratory aggregometers. RBC aggregation parameters were calculated, using the time course of impedance data often failed to correlate with known changes of aggregation, even reporting aggregation for cells in nonaggregating media (i.e., RBC in buffered saline). Alternatively, RBC aggregation parameters based upon the time course of capacitance data are in general agreement with those derived from LT data and with RBC aggregation indexes, measured using commercial instruments.

  3. A new method for electric impedance imaging using an eddy current with a tetrapolar circuit.

    PubMed

    Ahsan-Ul-Ambia; Toda, Shogo; Takemae, Tadashi; Kosugi, Yukio; Hongo, Minoru

    2009-02-01

    A new contactless technique for electrical impedance imaging, using an eddy current managed along with the tetrapolar circuit method, is proposed. The eddy current produced by a magnetic field is superimposed on a constant current that is normally used in the tetrapolar circuit method, and thus is used to control the current distribution in the body. By changing the current distribution, a set of voltage differences is measured with a pair of electrodes. This set of voltage differences is used in the image reconstruction of the resistivity distribution. The least square error minimization method is used in the reconstruction algorithm. The principle of this method is explained theoretically. A backprojection algorithm was used to get 2-D images. Based on this principle, a measurement system was developed and model experiments were conducted with a saline-filled phantom. The estimated shape of each model in the reconstructed image was similar to that of the corresponding model. From the results of these experiments, it is confirmed that the proposed method is applicable to the realization of electrical conductivity imaging.

  4. Remote detection of human electroencephalograms using ultrahigh input impedance electric potential sensors

    NASA Astrophysics Data System (ADS)

    Harland, C. J.; Clark, T. D.; Prance, R. J.

    2002-10-01

    In this letter, we demonstrate the use of very high performance, ultrahigh impedance, electric potential probes in the detection of electrical activity in the brain. We show that these sensors, requiring no electrical or physical contact with the body, can be used to monitor the human electroencephalogram (EEG) revealing, as examples, the α and β rhythms and the α blocking phenomenon. We suggest that the advantages offered by these sensors compared with the currently used contact (Ag/AgCl) electrodes may act to stimulate new developments in multichannel EEG monitoring and in real-time electrical imaging of the brain.

  5. A new method to measure the acoustic surface impedance outdoors.

    PubMed

    Carpinello, S; L'Hermite, Ph; Bérengier, M; Licitra, G

    2004-01-01

    In the European countries noise pollution is considered to be one of the most important environmental problems. With respect to traffic noise, different researchers are working on the reduction of noise at the source, on the modelling of the acoustic absorption of the road structure and on the effects of the pavement on the propagation. The aim of this paper is to propose a new method to measure the acoustic impedance of surfaces located outdoors, which allows us to further noise propagation models, in order to evaluate exactly the noise exposure.

  6. Auditory evoked field measurement using magneto-impedance sensors

    SciTech Connect

    Wang, K. Tajima, S.; Song, D.; Uchiyama, T.; Hamada, N.; Cai, C.

    2015-05-07

    The magnetic field of the human brain is extremely weak, and it is mostly measured and monitored in the magnetoencephalography method using superconducting quantum interference devices. In this study, in order to measure the weak magnetic field of the brain, we constructed a Magneto-Impedance sensor (MI sensor) system that can cancel out the background noise without any magnetic shield. Based on our previous studies of brain wave measurements, we used two MI sensors in this system for monitoring both cerebral hemispheres. In this study, we recorded and compared the auditory evoked field signals of the subject, including the N100 (or N1) and the P300 (or P3) brain waves. The results suggest that the MI sensor can be applied to brain activity measurement.

  7. Auditory evoked field measurement using magneto-impedance sensors

    NASA Astrophysics Data System (ADS)

    Wang, K.; Tajima, S.; Song, D.; Hamada, N.; Cai, C.; Uchiyama, T.

    2015-05-01

    The magnetic field of the human brain is extremely weak, and it is mostly measured and monitored in the magnetoencephalography method using superconducting quantum interference devices. In this study, in order to measure the weak magnetic field of the brain, we constructed a Magneto-Impedance sensor (MI sensor) system that can cancel out the background noise without any magnetic shield. Based on our previous studies of brain wave measurements, we used two MI sensors in this system for monitoring both cerebral hemispheres. In this study, we recorded and compared the auditory evoked field signals of the subject, including the N100 (or N1) and the P300 (or P3) brain waves. The results suggest that the MI sensor can be applied to brain activity measurement.

  8. System for simultaneous measurements of bilaterally symmetrical acupoints multifrequency impedances.

    PubMed

    Su, Mi-Yong; Tan, Yong-Hong; Wang, Zi-Min; Gan, Cai-Jun; Chen, Shou-Hong

    2013-01-01

    Devices which can obtain comparable bilaterally symmetrical acupoints (BSA) multifrequency impedances (MFI) are often needed in the detection of the energy balance states of acupoints in traditional Chinese medicine. To satisfy these needs, a two-channel impedance measurement system has been introduced which is capable of accurately and simultaneously measuring BSA MFI. The system includes a set of five electrodes, two of which are injected with exciting current signal to synchronously and equally excite BSA; the other three electrodes are used as sensors to simultaneously sense the response signal from both sides. The system also includes a PC-based time-domain signal testing platform with arbitrary current waveform generation and three channels (one exciting current and two response voltages) simultaneously sampling, and a set of MFI simultaneously unbiased computing algorithms based on special odd multisine current signal input. Preliminary validating experiments suggest that the system allows accurate and synchronous measurement of BSA MFI at least in the frequency range of 10 Hz to 60 kHz, and the obtained BSA MFI are well comparable.

  9. Spatial analysis of slowly oscillating electric activity in the gut of mice using low impedance arrayed microelectrodes.

    PubMed

    Taniguchi, Mizuki; Kajioka, Shunichi; Shozib, Habibul B; Sawamura, Kenta; Nakayama, Shinsuke

    2013-01-01

    Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ∼1 mm(2). The size of each recording electrode was 50×50 µm(2), however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/W(v) mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/W(v) mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity.

  10. 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.

  11. Optimization of Acoustic Pressure Measurements for Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Watson, W. R.; Nark, D. M.

    2007-01-01

    As noise constraints become increasingly stringent, there is continued emphasis on the development of improved acoustic liner concepts to reduce the amount of fan noise radiated to communities surrounding airports. As a result, multiple analytical prediction tools and experimental rigs have been developed by industry and academia to support liner evaluation. NASA Langley has also placed considerable effort in this area over the last three decades. More recently, a finite element code (Q3D) based on a quasi-3D implementation of the convected Helmholtz equation has been combined with measured data acquired in the Langley Grazing Incidence Tube (GIT) to reduce liner impedance in the presence of grazing flow. A new Curved Duct Test Rig (CDTR) has also been developed to allow evaluation of liners in the presence of grazing flow and controlled, higher-order modes, with straight and curved waveguides. Upgraded versions of each of these two test rigs are expected to begin operation by early 2008. The Grazing Flow Impedance Tube (GFIT) will replace the GIT, and additional capabilities will be incorporated into the CDTR. The current investigation uses the Q3D finite element code to evaluate some of the key capabilities of these two test rigs. First, the Q3D code is used to evaluate the microphone distribution designed for the GFIT. Liners ranging in length from 51 to 610 mm are investigated to determine whether acceptable impedance eduction can be achieved with microphones placed on the wall opposite the liner. This analysis indicates the best results are achieved for liner lengths of at least 203 mm. Next, the effects of moving this GFIT microphone array to the wall adjacent to the liner are evaluated, and acceptable results are achieved if the microphones are placed off the centerline. Finally, the code is used to investigate potential microphone placements in the CDTR rigid wall adjacent to the wall containing an acoustic liner, to determine if sufficient fidelity can be

  12. Detection of Chamber Conditioning Through Optical Emission and Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, Meyya

    2001-01-01

    During oxide etch processes, buildup of fluorocarbon residues on reactor sidewalls can cause run-to-run drift and will necessitate some time for conditioning and seasoning of the reactor. Though diagnostics can be applied to study and understand these phenomena, many of them are not practical for use in an industrial reactor. For instance, measurements of ion fluxes and energy by mass spectrometry show that the buildup of insulating fluorocarbon films on the reactor surface will cause a shift in both ion energy and current in an argon plasma. However, such a device cannot be easily integrated into a processing system. The shift in ion energy and flux will be accompanied by an increase in the capacitance of the plasma sheath. The shift in sheath capacitance can be easily measured by a common commercially available impedance probe placed on the inductive coil. A buildup of film on the chamber wall is expected to affect the production of fluorocarbon radicals, and thus the presence of such species in the optical emission spectrum of the plasma can be monitored as well. These two techniques are employed on a GEC (Gaseous Electronics Conference) Reference Cell to assess the validity of optical emission and impedance monitoring as a metric of chamber conditioning. These techniques are applied to experimental runs with CHF3 and CHF3/O2/Ar plasmas, with intermediate monitoring of pure argon plasmas as a reference case for chamber conditions.

  13. Spatial-temporal modeling for electrical impedance imaging of a mixing process

    NASA Astrophysics Data System (ADS)

    West, R. M.; Meng, S.; Aykroyd, R. G.; Williams, R. A.

    2005-07-01

    The use of electrical tomography techniques for process visualization and investigation is a well-known example of a nonlinear, ill-posed, and underdetermined inverse problem. Hence stable and reliable solution is not possible using measured data alone, but requires regularization through prior information. The rôle of a Bayesian approach is therefore of fundamental importance, and when coupled with Markov chain Monte Carlo (MCMC) sampling, it can provide valuable statistical information about solution behavior and reliability, which is in contrast to most current approaches which provide only a single image reconstruction with unquantified errors. For many applications of dynamic electrical impedance imaging, some degree of both spatial and temporal smoothness is expected. Often temporal smoothness is ignored and only spatial smoothing is used. In the current application, the addition of an aliquot to a mixing vessel, smoothness is not appropriate prior information. Instead an aliquot prior is proposed, parameterized in terms of location, size, and resistivity. This approach leads to data-driven and adaptive smoothing, in contrast to the more usual global smoothing of standard regularization methods. Of further interest is the inclusion of temporal prior information: it is known that the aliquot moves and disperses in a specific manner. With this added temporal information, imaging is improved as are derived process parameters.

  14. Measurement of the coupling impedances of the kickers in the SIS and ESR at GSI.

    NASA Astrophysics Data System (ADS)

    Blell, U.

    1997-05-01

    At high particle intensities coherent transverse beam oscillations may be excited due to the coupling of the beam to individual accelerators structures. The characteristic values to describe these beam instabilities are the longitudinal- and transverse coupling impedances. One reason for this beam instability is the inductive interaction between the beam and the kicker magnets. The type of the magnet, e.g. window-frame magnet or C-magnet, and its external electrical network are the most important quantities to identify the coupling impedances below the cut-off frequency of the beam pipe. For the kicker modules in the SIS and ESR accelerators at GSI the mathematical basis, theory and measured results will be presented.

  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. Investigation of low frequency electrolytic solution behavior with an accurate electrical impedance method

    NASA Astrophysics Data System (ADS)

    Ho, Kung-Chu; Su, Vin-Cent; Huang, Da-Yo; Lee, Ming-Lun; Chou, Nai-Kuan; Kuan, Chieh-Hsiung

    2017-01-01

    This paper reports the investigation of strong electrolytic solutions operated in low frequency regime through an accurate electrical impedance method realized with a specific microfluidic device and high resolution instruments. Experimental results show the better repeatability and accuracy of the proposed impedance method. Moreover, all electrolytic solutions appear the so-called relaxation frequency at each peak value of dielectric loss due to relaxing total polarization inside the device. The relaxation frequency of concentrated electrolytes becomes higher owing to the stronger total polarization behavior coming from the higher conductivity as well as the lower resistance in the electrolytic solutions.

  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. Effect of diffusion on impedance measurements in a hydrodynamic flow focusing sensor.

    PubMed

    Nasir, Mansoor; Price, Dorielle T; Shriver-Lake, Lisa C; Ligler, Frances

    2010-10-21

    This paper investigated the effects of diffusion between non-conductive sheath and conductive sample fluids in an impedance-based biosensor. Impedance measurements were made with 2- and 4-electrode configurations. The 4-electrode design offers the advantage of impedance measurements at low frequencies (<1 kHz) without the deleterious effects of double layer impedance which are present in the 2-electrode design. Hydrodynamic flow focusing was achieved with a modified T-junction design with a smaller cross-section for the sample channel than for the focusing channel, which resulted in 2D focusing of the sample stream with just one sheath stream. By choosing a non-conductive sheath fluid and a conductive sample fluid, the electric field was confined to the focused stream. In order to utilize this system for biosensing applications, we characterized it for electrical and flow parameters. In particular, we investigated the effects of varying flow velocities and flow-rate ratios on the focused stream. Increasing flow-rate ratios reduced the cross-sectional area of the focused streams as was verified by finite element modeling and confocal microscopy. Antibody mediated binding of Escherichia coli to the electrode surface caused an increase in solution resistance at low frequencies. The results also showed that the diffusion mass transport at the interface of the two streams limited the benefits of increased flow focusing. Increasing flow velocities could be used to offset the diffusion effect. To optimize detection sensitivity, flow parameters and mass transport must be considered in conjunction, with the goal of reducing diffusion of conducting species out of the focused stream while simultaneously minimizing its cross-sectional area.

  19. Static conductivity imaging using variational gradient Bz algorithm in magnetic resonance electrical impedance tomography.

    PubMed

    Park, Chunjae; Park, Eun-Jae; Woo, Eung Je; Kwon, Ohin; Seo, Jin Keun

    2004-02-01

    A new image reconstruction algorithm is proposed to visualize static conductivity images of a subject in magnetic resonance electrical impedance tomography (MREIT). Injecting electrical current into the subject through surface electrodes, we can measure the induced internal magnetic flux density B = (Bx, By, Bz) using an MRI scanner. In this paper, we assume that only the z-component Bz is measurable due to a practical limitation of the measurement technique in MREIT. Under this circumstance, a constructive MREIT imaging technique called the harmonic Bz algorithm was recently developed to produce high-resolution conductivity images. The algorithm is based on the relation between inverted delta2Bz and the conductivity requiring the computation of inverted delta2Bz. Since twice differentiations of noisy Bz data tend to amplify the noise, the performance of the harmonic Bz algorithm is deteriorated when the signal-to-noise ratio in measured Bz data is not high enough. Therefore, it is highly desirable to develop a new algorithm reducing the number of differentiations. In this work, we propose the variational gradient Bz algorithm where Bz is differentiated only once. Numerical simulations with added random noise confirmed its ability to reconstruct static conductivity images in MREIT. We also found that it outperforms the harmonic Bz algorithm in terms of noise tolerance. From a careful analysis of the performance of the variational gradient Bz algorithm, we suggest several methods to further improve the image quality including a better choice of basis functions, regularization technique and multilevel approach. The proposed variational framework utilizing only Bz will lead to different versions of improved algorithms.

  20. Real time three-dimensional electrical impedance tomography applied in multiphase flow imaging

    NASA Astrophysics Data System (ADS)

    Heikkinen, L. M.; Kourunen, J.; Savolainen, T.; Vauhkonen, P. J.; Kaipio, J. P.; Vauhkonen, M.

    2006-08-01

    In many industrial applications the aim is to obtain information on three-dimensional (3D) material distribution within the process vessels. With standard two-dimensional (2D) techniques only vague cross-sectional information can be obtained. It could be possible to carry out several 2D reconstructions on different layers and in this way to obtain 3D information. However, in this approach errors are induced since no real 3D information is utilized in the image reconstruction. In this paper we describe an approach to measure, reconstruct and visualize three-dimensional electrical impedance tomography images in real time. The reconstruction is based on a difference imaging scheme. An efficient current injection and voltage measurement protocol is used in order to increase the sensitivity and reduce the data collection time. The proposed approach can produce and visualize up to 15 3D EIT images per second when 80 measurement electrodes are used. Imaging results from a stirred vessel and a flow loop will be shown. The reconstructions show, for example, that 3D air/liquid distribution in the stirred vessel can reliably be visualized in real time and material flow can be monitored in a 3D section of the flow loop. Reconstructions can be visualized and analysed in many different ways in order to produce essential information on the behaviour of the processes.

  1. The Bayesian approximation error approach for electrical impedance tomography—experimental results

    NASA Astrophysics Data System (ADS)

    Nissinen, A.; Heikkinen, L. M.; Kaipio, J. P.

    2008-01-01

    Inverse problems can be characterized as problems that tolerate measurement and modelling errors poorly. While the measurement error issue has been widely considered as a solved problem, the modelling errors have remained largely untreated. The approximation and modelling errors can, however, be argued to dominate the measurement errors in most applications. There are several applications in which the temporal and memory requirements dictate that the computational complexity of the forward solver be radically reduced. For example, in process tomography the reconstructions have to be carried out typically in a few tens of milliseconds. Recently, a Bayesian approach for the treatment of approximation and modelling errors for inverse problems has been proposed. This approach has proven to work well in several classes of problems, but the approach has not been verified in any problem with real data. In this paper, we study two different types of modelling errors in the case of electrical impedance tomography: one related to model reduction and one concerning partially unknown geometry. We show that the approach is also feasible in practice and may facilitate the reduction of the computational complexity of the nonlinear EIT problem at least by an order of magnitude.

  2. Direct inversion from partial-boundary data in electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Hauptmann, Andreas; Santacesaria, Matteo; Siltanen, Samuli

    2017-02-01

    In electrical impedance tomography (EIT) one wants to image the conductivity distribution of a body from current and voltage measurements carried out on its boundary. In this paper we consider the underlying mathematical model, the inverse conductivity problem, in two dimensions and under the realistic assumption that only a part of the boundary is accessible to measurements. In this framework our data are modeled as a partial Neumann-to-Dirichlet map (ND map). We compare this data to the full-boundary ND map and prove that the error depends linearly on the size of the missing part of the boundary. The same linear dependence is further proved for the difference of the reconstructed conductivities—from partial and full boundary data. The reconstruction is based on a truncated and linearized D-bar method. Auxiliary results include an extrapolation method to estimate the full-boundary data from the measured one, an approximation of the complex geometrical optics solutions computed directly from the ND map as well as an approximate scattering transform for reconstructing the conductivity. Numerical verification of the convergence results and reconstructions are presented for simulated test cases.

  3. Antenna impedance measurements in a magnetized plasma. I. Spherical antenna

    SciTech Connect

    Blackwell, David D.; Walker, David N.; Messer, Sarah J.; Amatucci, William E.

    2007-09-15

    The input impedance of a metal sphere immersed in a magnetized plasma is measured with a network analyzer at frequencies up to 1 GHz. The experiments were done in the Space Physics Simulation Chamber at the Naval Research Laboratory. The hot-filament argon plasma was varied between weakly ({omega}{sub ce}<{omega}{sub pe}) and strongly ({omega}{sub ce}>{omega}{sub pe}) magnetized plasma with electron densities in the range 10{sup 7}-10{sup 10} cm{sup -3}. It is observed that the lower-frequency resonance of the impedance characteristic previously associated with series sheath resonance {omega}{sub sh} in the unmagnetized plasma occurs at a hybrid sheath frequency of {omega}{sub r}{sup 2}={omega}{sub sh}{sup 2}+{kappa}{omega}{sub ce}{sup 2}, where {kappa} is a constant 0.5<{kappa}<1. As seen in previous experiments, the higher frequency resonance associated with the electron plasma frequency {omega}{sub pe} in the unmagnetized plasma is relocated to the upper hybrid frequency {omega}{sub uh}{sup 2}={omega}{sub pe}{sup 2}+{omega}{sub ce}{sup 2}. As with the unmagnetized plasma, the maximum power deposition occurs at the lower frequency resonance {omega}{sub r}.

  4. 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.

  5. 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.

  6. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

    2004-06-16

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 0.1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002, Tseng et al., 2003). Electric and magnetic sensors are being tested and calibrated on sea water and in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  7. High Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Framgos, William

    1999-06-01

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  8. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

    2002-11-20

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  9. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen; Choi, Youngki

    2001-06-10

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  10. High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring, and Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex

    2000-06-01

    Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach (Song et al., 1997). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.

  11. Microfluidic chip with integrated electrical cell-impedance sensing for monitoring single cancer cell migration in three-dimensional matrixes.

    PubMed

    Nguyen, Tien Anh; Yin, Tsung-I; Reyes, Diego; Urban, Gerald A

    2013-11-19

    Cell migration has been recognized as one hallmark of malignant tumor progression. By integrating the method of electrical cell-substrate impedance sensing (ECIS) with the Boyden chamber design, the state-of-the-art techniques provide kinetic information about cell migration and invasion processes in three-dimensional (3D) extracellular matrixes. However, the information related to the initial stage of cell migration with single-cell resolution, which plays a unique role in the metastasis-invasion cascade of cancer, is not yet available. In this paper, we present a microfluidic device integrated with ECIS for investigating single cancer cell migration in 3D matrixes. Using microfluidics techniques without the requirement of physical connections to off-chip pneumatics, the proposed sensor chip can efficiently capture single cells on microelectrode arrays for sequential on-chip 2D or 3D cell culture and impedance measurement. An on-chip single-cell migration assay was successfully demonstrated within several minutes. Migration of single metastatic MDA-MB-231 cells in their initial stage can be monitored in real time; it shows a rapid change in impedance magnitude of approximately 10 Ω/s, whereas no prominent impedance change is observed for less-metastasis MCF-7 cells. The proposed sensor chip, allowing for a rapid and selective detection of the migratory properties of cancer cells at the single-cell level, could be applied as a new tool for cancer research.

  12. Non-invasive determination of absolute lung resistivity in adults using electrical impedance tomography.

    PubMed

    Zhang, Jie; Patterson, Robert

    2010-08-01

    Lung resistivity is a physiological parameter that describes the electrical characteristics of the lungs. Lung composition changes due to changes in the lung tissues, fluid and air volume. Various diseases that can cause a change in lung composition may be monitored by measuring lung resistivity. Currently, there is no accepted non-invasive method to measure lung resistivity. In this study, we presented a method and framework to non-invasively determine lung resistivity using electrical impedance tomography (EIT). By comparing actual measurements from subjects with data from a 3D human thorax model, an EIT image can be reconstructed to show a resistivity difference between the model and the subject. By adjusting the lung resistivity in the model, the resistivity difference in the lung regions can be reduced to near zero. This resistivity value then is the estimation of the lung resistivity of the subject. Using the proposed method, the lung resistivities of four normal adult males (43 +/- 13 years, 78 +/- 10 kg) in the supine position at air volumes starting at functional residual capacity (FRC--end expiration) and increasing in 0.5 l steps to 1.5 l were studied. The averaged lung resistivity changes 12.59%, from 1406 Omega cm to 1583 Omega cm, following the inspiration of 1.5 l air from FRC. The coefficients of variation (CV) of precision for the four subjects are less than 10%. The experiment was repeated five times at each air volume on a subject to test the reproducibility. The CVs are less than 3%. The results show that it is feasible to determine absolute lung resistivity using an EIT-based method.

  13. Method to detect the end-point for PCR DNA amplification using an ionically labeled probe and measuring impedance change

    DOEpatents

    Miles, Robin R.; Belgrader, Phillip; Fuller, Christopher D.

    2007-01-02

    Impedance measurements are used to detect the end-point for PCR DNA amplification. A pair of spaced electrodes are located on a surface of a microfluidic channel and an AC or DC voltage is applied across the electrodes to produce an electric field. An ionically labeled probe will attach to a complementary DNA segment, and a polymerase enzyme will release the ionic label. This causes the conductivity of the solution in the area of the electrode to change. This change in conductivity is measured as a change in the impedance been the two electrodes.

  14. 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

  15. 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.

  16. Dependence of Impedance Measurement Sensitivity of Cell Growth on Sensing Area of Circular Interdigitated Electrode.

    PubMed

    Park, Jinsoo; Hwang, Kyo Seon; Cho, Sungbo

    2015-10-01

    A circular interdigitated electrode (IDE) array for label-free and real-time impedance monitoring of cell growth was fabricated and evaluated. Both the width and spacing of fingers were 50 μm, and the exposed sensing area of the circular IDE was 1.3~3.4 mm. The electrical characteristics of the fabricated circular IDE were modeled as an equivalent circuit, and the values of the circuit parameters extrapolated from the fitting to the measured spectra in different concentrations of NaCl or sensing areas of the circular IDE were analyzed. During cell growth, the resistance of cells extrapolated from the fitting was increased and the maximum rate of change in the real part of the impedance was observed at frequencies of 10 to 22 kHz. The normalized real part of the impedance measured at 10 kHz during cell growth was increased more with decreasing the electrode sensing area, albeit the number of cells to be investigated showed a corresponding increase.

  17. A direct method for measuring acoustic ground impedance in long-range propagation experiments.

    PubMed

    Soh, Jin H; Gilbert, Kenneth E; Frazier, W M Garth; Talmadge, Carrick L; Waxler, Roger

    2010-11-01

    A method is reported for determining ground impedance in long-range propagation experiments by using the definition of impedance directly. The method is envisioned as way of measuring the impedence at multiple locations along the propagation path, using the signals broadcast during the experiment itself. In a short-range (10 m) test, the direct method was in good agreement with a more conventional model-based least-squares method. The utility of the direct method was demonstrated in a 400 m propagation experiment in a agricultural field. The resulting impedance was consistent with the impedance measured previously in the same field.

  18. Accuracy of two osmometers on standard samples: electrical impedance technique and freezing point depression technique

    NASA Astrophysics Data System (ADS)

    García-Resúa, Carlos; Pena-Verdeal, Hugo; Miñones, Mercedes; Gilino, Jorge; Giraldez, Maria J.; Yebra-Pimentel, Eva

    2013-11-01

    High tear fluid osmolarity is a feature common to all types of dry eye. This study was designed to establish the accuracy of two osmometers, a freezing point depression osmometer (Fiske 110) and an electrical impedance osmometer (TearLab™) by using standard samples. To assess the accuracy of the measurements provided by the two instruments we used 5 solutions of known osmolarity/osmolality; 50, 290 and 850 mOsm/kg and 292 and 338 mOsm/L. Fiske 110 is designed to be used in samples of 20 μl, so measurements were made on 1:9, 1:4, 1:1 and 1:0 dilutions of the standards. Tear Lab is addressed to be used in tear film and only a sample of 0.05 μl is required, so no dilutions were employed. Due to the smaller measurement range of the TearLab, the 50 and 850 mOsm/kg standards were not included. 20 measurements per standard sample were used and differences with the reference value was analysed by one sample t-test. Fiske 110 showed that osmolarity measurements differed statistically from standard values except those recorded for 290 mOsm/kg standard diluted 1:1 (p = 0.309), the 292 mOsm/L H2O sample (1:1) and 338 mOsm/L H2O standard (1:4). The more diluted the sample, the higher the error rate. For the TearLab measurements, one-sample t-test indicated that all determinations differed from the theoretical values (p = 0.001), though differences were always small. For undiluted solutions, Fiske 110 shows similar performance than TearLab. However, for the diluted standards, Fiske 110 worsens.

  19. High-Frequency and Very-high-Frequency (HF&VHF) above-groundelectromagnetic impedance measurements

    SciTech Connect

    Frangos, William; Becker, Alex; Lee, K.H.

    2002-09-20

    We have field-tested an apparatus for measuring the electromagnetic impedance above the ground at a plurality of frequencies in the 0.3 - 30 MHz range. This window in the frequency spectrum, which lies between frequencies used for GPR and those used for conventional loop-loop EM soundings, has not been used because of difficulties in fielding equipment for making absolute and accurate measurements. Model and physical parameter studies however confirm that data in this frequency band can be used to construct high-resolution maps of electrical conductivity and permittivity of near-surface material. Our equipment was assembled using commercial electric and magnetic antennas. The magnetic loop source is excited by a conventional signal generator - power amplifier assembly. Signal detection is accomplished using RF lock-in amplifiers. All system elements are appropriately isolated by optic - fiber links. We estimate a measurement accuracy of about {+-} 10% for an 8-m separation between source and detector. Field tests were done at the University of California Richmond Field Station where the near surface electrical structure is well known. The experimental data at this site are mainly a function of electrical conductivity. In this context, we have obtained good agreement with the known local variations in resistivity both with depth and with position along a 35-m traverse. Additional tests in more resistive regimes where dielectric permittivity is not negligible yield spectral data compatible with the less well known near-surface electrical properties.

  20. Evaluation of Electrical Impedance as a Biomarker of Myostatin Inhibition in Wild Type and Muscular Dystrophy Mice

    PubMed Central

    Sanchez, Benjamin; Li, Jia; Yim, Sung; Pacheck, Adam; Widrick, Jeffrey J.; Rutkove, Seward B.

    2015-01-01

    Objectives Non-invasive and effort independent biomarkers are needed to better assess the effects of drug therapy on healthy muscle and that affected by muscular dystrophy (mdx). Here we evaluated the use of multi-frequency electrical impedance for this purpose with comparison to force and histological parameters. Methods Eight wild-type (wt) and 10 mdx mice were treated weekly with RAP-031 activin type IIB receptor at a dose of 10 mg kg−1 twice weekly for 16 weeks; the investigators were blinded to treatment and disease status. At the completion of treatment, impedance measurements, in situ force measurements, and histology analyses were performed. Results As compared to untreated animals, RAP-031 wt and mdx treated mice had greater body mass (18% and 17%, p < 0.001 respectively) and muscle mass (25% p < 0.05 and 22% p < 0.001, respectively). The Cole impedance parameters in treated wt mice, showed a 24% lower central frequency (p < 0.05) and 19% higher resistance ratio (p < 0.05); no significant differences were observed in the mdx mice. These differences were consistent with those seen in maximum isometric force, which was greater in the wt animals (p < 0.05 at > 70 Hz), but not in the mdx animals. In contrast, maximum force normalized by muscle mass was unchanged in the wt animals and lower in the mdx animals by 21% (p < 0.01). Similarly, myofiber size was only non-significantly higher in treated versus untreated animals (8% p = 0.44 and 12% p = 0.31 for wt and mdx animals, respectively). Conclusions Our findings demonstrate electrical impedance of muscle reproduce the functional and histological changes associated with myostatin pathway inhibition and do not reflect differences in muscle size or volume. This technique deserves further study in both animal and human therapeutic trials. PMID:26485280

  1. 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.

  2. Electrical impedance and HV plasma images of high dilutions of sodium chloride.

    PubMed

    Assumpção, R

    2008-07-01

    This paper reports impedance data and high voltage plasma photographic plates of high dilutions of sodium chloride in water submitted to the homeopathic dilution and succession up to 30cH. Extremely low concentrations of the original salt, even beyond Avogadro number, clearly differ from 'pure' water and; the action of sodium chloride on the electrical properties of water is inverted at high dilution.

  3. dc-Electrical Degradation of the BT-Based Material for Multilayer Ceramic Capacitor with Ni internal Electrode: Impedance Analysis and Microstructure

    NASA Astrophysics Data System (ADS)

    Chazono, Hirokazu; Kishi, Hiroshi

    2001-09-01

    The impedance of a BaTiO3 (BT)-based multilayer ceramic capacitor with a nickel internal electrode (Ni-MLCC) was investigated by measuring the frequency domain at various temperatures. All the obtained impedance data could be successfully fitted to a 4-RC section electrical equivalent network. The 4-RC section electrical equivalent network was successfully correlated to the microstructure: the core, the shell, the grain boundary, and the ceramic/internal electrode interface regions. Based on this electrical equivalent network, the electrical properties including the Curie-Weiss law, the current-voltage characteristics, and dc electrical degradation, were well explained. A model for the degradation behavior for BT-based Ni-MLCC with thin active layer thickness was proposed.

  4. 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.

  5. 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.

  6. 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.

  7. Accelerated reconstruction of electrical impedance tomography images via patch based sparse representation

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Lian, Zhijie; Wang, Jianming; Chen, Qingliang; Sun, Yukuan; Li, Xiuyan; Duan, Xiaojie; Cui, Ziqiang; Wang, Huaxiang

    2016-11-01

    Electrical impedance tomography (EIT) reconstruction is a nonlinear and ill-posed problem. Exact reconstruction of an EIT image inverts a high dimensional mathematical model to calculate the conductivity field, which causes significant problems regarding that the computational complexity will reduce the achievable frame rate, which is considered as a major advantage of EIT imaging. The single-step method, state estimation method, and projection method were always used to accelerate reconstruction process. The basic principle of these methods is to reduce computational complexity. However, maintaining high resolution in space together with not much cost is still challenging, especially for complex conductivity distribution. This study proposes an idea to accelerate image reconstruction of EIT based on compressive sensing (CS) theory, namely, CSEIT method. The novel CSEIT method reduces the sampling rate through minimizing redundancy in measurements, so that detailed information of reconstruction is not lost. In order to obtain sparse solution, which is the prior condition of signal recovery required by CS theory, a novel image reconstruction algorithm based on patch-based sparse representation is proposed. By applying the new framework of CSEIT, the data acquisition time, or the sampling rate, is reduced by more than two times, while the accuracy of reconstruction is significantly improved.

  8. 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.

  9. Electrical Cell-Substrate Impedance Spectroscopy Can Monitor Age-Grouped Human Adipose Stem Cell Variability During Osteogenic Differentiation.

    PubMed

    Nordberg, Rachel C; Zhang, Jianlei; Griffith, Emily H; Frank, Matthew W; Starly, Binil; Loboa, Elizabeth G

    2017-02-01

    Human adipose stem cells (hASCs) are an attractive cell source for bone tissue engineering applications. However, a critical issue to be addressed before widespread hASC clinical translation is the dramatic variability in proliferative capacity and osteogenic potential among hASCs isolated from different donors. The goal of this study was to test our hypothesis that electrical cell-substrate impedance spectroscopy (ECIS) could track complex bioimpedance patterns of hASCs throughout proliferation and osteogenic differentiation to better understand and predict variability among hASC populations. Superlots composed of hASCs from young (aged 24-36 years), middle-aged (aged 48-55 years), and elderly (aged 60-81 years) donors were seeded on gold electrode arrays. Complex impedance measurements were taken throughout proliferation and osteogenic differentiation. During osteogenic differentiation, four impedance phases were identified: increase, primary stabilization, drop phase, and secondary stabilization. Matrix deposition was first observed 48-96 hours after the impedance maximum, indicating, for the first time, that ECIS can identify morphological changes that correspond to late-stage osteogenic differentiation. The impedance maximum was observed at day 10.0 in young, day 6.1 in middle-aged, and day 1.3 in elderly hASCs, suggesting that hASCs from younger donors require a longer time to differentiate than do hASCs from older donors, but young hASCs proliferated more and accreted more calcium long-term. This is the first study to use ECIS to predict osteogenic potential of multiple hASC populations and to show that donor age may temporally control onset of osteogenesis. These findings could be critical for development of patient-specific bone tissue engineering and regenerative medicine therapies. Stem Cells Translational Medicine 2017;6:502-511.

  10. Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn-Mn ferrites

    SciTech Connect

    Hankare, P.P.; Patil, R.P.; Garadkar, K.M.; Sasikala, R.; Chougule, B.K.

    2011-03-15

    Graphical abstract: Variation of dielectric constant with frequency. Research highlights: {yields} Sol-gel route synthesized spherical crystalline nanoparticles of ZnMn{sub 1-x}Cr{sub x}FeO{sub 4}. {yields} XRD, DTA, FTIR, SEM, dielectric and impedance study. {yields} The ferrites show concentration dependence of ac electrical conductivity. {yields} Impedance response is dominated by grain boundary behavior. -- Abstract: Nanocrystalline ZnMn{sub 1-x}Cr{sub x}FeO{sub 4} (1.0 {>=} x {>=} 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm{sup -1} arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.

  11. Method of utility-system source-impedance measurement for the industrial power engineer

    SciTech Connect

    Corvin, W C

    1982-05-24

    In general, the power company that delivers energy to an industrial power system will supply, upon request, information describing the utility source impedance at the point of interconnection with the industrial customer. this information is usually expressed as the maximum available short-circuit MVA (megavolt amperes) that the utility can deliver at some nominal voltage. For sizing the interrupting ratings of protective equipment, this number is important. However, better information is required for modeling the utility system under all conditions of system switching, generation, and loading. In this paper a method is described for measuring the utility source impedance that gives a more realistic representation of the utility at the point of interconnection. It is increasingly important that the industrial power engineer accurately view the power company as a power source of variable impedance. Industrial loads may operate and interact differently, depending on the relative stiffness of their power source. Electric utilities increasingly experience planned voltage reductions, brownouts, and temporary line-switching configurations that can leave the industrial customer with a power source far different from the one normally expected.

  12. AN ADVANCED CALIBRATION PROCEDURE FOR COMPLEX IMPEDANCE SPECTRUM MEASUREMENTS OF ADVANCED ENERGY STORAGE DEVICES

    SciTech Connect

    William H. Morrison; Jon P. Christophersen; Patrick Bald; John L. Morrison

    2012-06-01

    With the increasing demand for electric and hybrid electric vehicles and the explosion in popularity of mobile and portable electronic devices such as laptops, cell phones, e-readers, tablet computers and the like, reliance on portable energy storage devices such as batteries has likewise increased. The concern for the availability of critical systems in turn drives the availability of battery systems and thus the need for accurate battery health monitoring has become paramount. Over the past decade the Idaho National Laboratory (INL), Montana Tech of the University of Montana (Tech), and Qualtech Systems, Inc. (QSI) have been developing the Smart Battery Status Monitor (SBSM), an integrated battery management system designed to monitor battery health, performance and degradation and use this knowledge for effective battery management and increased battery life. Key to the success of the SBSM is an in-situ impedance measurement system called the Impedance Measurement Box (IMB). One of the challenges encountered has been development of an accurate, simple, robust calibration process. This paper discusses the successful realization of this process.

  13. Electrical Impedance Tomography: a new study method for neonatal Respiratory Distress Syndrome?

    PubMed

    Chatziioannidis, I; Samaras, T; Nikolaidis, N

    2011-07-01

    Treatment of cardiorespiratory system diseases is a procedure that usually demands data collection on terms of the anatomy and the operation of the organs that are under study. Electrical Impedance Tomography (EIT) is an alternative approach, in comparison to existing techniques. With EIT electrodes are placed in the perimeter of the human body and images of the estimated organ are reconstructed, using the measurement of its impendence (or resistance) distribution and determining its alteration through time, while at the same time the patient is not exposed to ionizing radiation. Its clinical use presupposes the correct placement of the electrodes over the perimeter of the human body, the rapid data collection and electrical safety. It is a low cost technique and it is implemented near the patient. It is able to determine the distribution of ventilation, blood supply, diffused or localized lung defects, but it can also estimate therapeutic interventions or alteration to assisted ventilation of the neonate. EIT was developed at the beginning of the 1980s, but it has only recently begun to be implemented on neonates, and especially in the study of their respiratory system function. The low rate of image analysis is considered to be a drawback, but it is offset by the potential offered for the estimation of lungs' function (both under normal and pathological conditions), since ventilation and resistance are two quite similar concepts. In this review the most important studies about EIT are mentioned as a method of estimating respiratory distress syndrome in neonates. In terms of the above mentioned development, it is supposed that this technique will offer a great amount of help to the doctor in his / her estimations of the cardiorespiratory system and to his / her selection of the best intervening strategies.

  14. 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.

  15. 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.

  16. THE COUPLING AND MUTUAL IMPEDANCE BETWEEN BALANCED WIRE-ARM CONICAL LOG-SPIRAL ANTENNAS

    DTIC Science & Technology

    CONICAL ANTENNAS, *COUPLED ANTENNAS, * HELICAL ANTENNAS, ANTENNA COMPONENTS, ANTENNA RADIATION PATTERNS, COUPLINGS, DESIGN, ELECTRIC CURRENTS...ELECTRIC POTENTIAL, ELECTRICAL IMPEDANCE, MEASUREMENT, POLARIZATION, PROPAGATION, ROTATION, SPIRAL ANTENNAS, THEORY

  17. Impedance Measurement for the Analysis of Corrosion Induced Failures.

    DTIC Science & Technology

    1982-02-01

    for a C-Mn Steel (C1117) in 1 M Na3PO4 , pH=4, T-21 C and in 1.0 M NaHCO3/0.1 M Na CO, T=70 C at controlled potentials with continuous recording of the...Impedance Parameters for C1117 Steel in 1 N Na3PO4 , pH = 4.............................................. 25 IV A.C. Impedance Parameters for Al 7075...CERT with continuous recording of the ac impedance.........................5 2 Anodic potentiodynamic polarization curves for 1008 steel in 1N Na3PO4

  18. 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.

  19. Conductivity and current density image reconstruction using harmonic Bz algorithm in magnetic resonance electrical impedance tomography.

    PubMed

    Oh, Suk Hoon; Lee, Byung Il; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyoung; Kwon, Ohin; Seo, Jin Keun

    2003-10-07

    Magnetic resonance electrical impedance tomography (MREIT) is to provide cross-sectional images of the conductivity distribution sigma of a subject. While injecting current into the subject, we measure one component Bz of the induced magnetic flux density B = (Bx, By, Bz) using an MRI scanner. Based on the relation between (inverted delta)2 Bz and inverted delta sigma, the harmonic Bz algorithm reconstructs an image of sigma using the measured Bz data from multiple imaging slices. After we obtain sigma, we can reconstruct images of current density distributions for any given current injection method. Following the description of the harmonic Bz algorithm, this paper presents reconstructed conductivity and current density images from computer simulations and phantom experiments using four recessed electrodes injecting six different currents of 26 mA. For experimental results, we used a three-dimensional saline phantom with two polyacrylamide objects inside. We used our 0.3 T (tesla) experimental MRI scanner to measure the induced Bz. Using the harmonic Bz algorithm, we could reconstruct conductivity and current density images with 82 x 82 pixels. The pixel size was 0.6 x 0.6 mm2. The relative L2 errors of the reconstructed images were between 13.8 and 21.5% when the signal-to-noise ratio (SNR) of the corresponding MR magnitude images was about 30. The results suggest that in vitro and in vivo experimental studies with animal subjects are feasible. Further studies are requested to reduce the amount of injection current down to less than 1 mA for human subjects.

  20. 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.

  1. A wideband high common mode rejection ratio amplifier and phase-locked loop demodulator for multifrequency impedance measurement.

    PubMed

    Goovaerts, H G; Faes, T J; Raaijmakers, E; Heethaar, R M

    1998-11-01

    Design considerations and implementation of a multifrequency measuring channel for application in the field of bio-impedance measurement are discussed in this paper. The input amplifier has a differential configuration which is electrically isolated from the remaining circuits. Transformer coupling provides improved common mode rejection when compared to non-isolated input stages. The frequency characteristic of the section between input and demodulator is flat within +/- 0.1 dB between 4 kHz and 1024 kHz. The synchronous demodulator is based on a wideband switched video amplifier. In contrast to commonly used lock--in techniques, the carrier for demodulation is recovered from the input signal by means of a phase-locked loop. This method ensures zero phase shift with respect to the input signal and improves the accuracy of measurement. The system has been developed primarily for thoracic impedance cardiography (TIC) but has also successfully been applied in the field of total body bio-impedance analysis (BIA). At present an electrical impedance tomograph is under development based on the instrumentation described. Results regarding the measurement range and accuracy are given and some recordings of patient data are shown.

  2. Continuous Non-Invasive Monitoring of Tidal Volumes by Measurement of Tidal Impedance in Neonatal Piglets

    PubMed Central

    Kurth, Florian; Zinnow, Fabienne; Prakapenia, Alexandra; Dietl, Sabrina; Winkler, Stefan; Ifflaender, Sascha; Rüdiger, Mario; Burkhardt, Wolfram

    2011-01-01

    Background Electrical Impedance measurements can be used to estimate the content of intra-thoracic air and thereby give information on pulmonary ventilation. Conventional Impedance measurements mainly indicate relative changes, but no information concerning air-volume is given. The study was performed to test whether a 3-point-calibration with known tidal volumes (VT) during conventional mechanical ventilation (CMV) allows subsequent calculation of VT from total Tidal-Impedance (tTI) measurements using Quadrant Impedance Measurement (QIM). In addition the distribution of TI in different regions of the thorax was examined. Methodology and Principal Findings QIM was performed in five neonatal piglets during volume-controlled CMV. tTI values at three different VT (4, 6, 8 ml/kg) were used to establish individual calibration curves. Subsequently, each animal was ventilated with different patterns of varying VT (2–10 ml/kg) at different PEEP levels (0, 3, 6, 9, 12 cmH2O). VT variation was repeated after surfactant depletion by bronchoalveolar lavage. VT was calculated from tTI values (VTcalc) and compared to the VT delivered by the ventilator (VTPNT). Bland-Altman analysis revealed good agreement between VTcalc and VTPNT before (bias −0.08 ml; limits of agreement −1.18 to 1.02 ml at PEEP = 3 cmH2O) and after surfactant depletion (bias −0.17 ml; limits of agreement −1.57 to 1.22 ml at PEEP = 3 cmH2O). At higher PEEP levels VTcalc was lower than VTPNT, when only one fixed calibration curve (at PEEP 3 cmH2O) was used. With a new calibration curve at each PEEP level the method showed similar accuracy at each PEEP level. TI showed a homogeneous distribution over the four assessed quadrants with a shift toward caudal regions of the thorax with increasing VT. Conclusion Tidal Impedance values could be used for precise and accurate calculation of VT during CMV in this animal study, when calibrated at each PEEP level. PMID:21687746

  3. Towards on line monitoring the evolution of the myocardium infarction scar with an implantable electrical impedance spectrum monitoring system.

    PubMed

    Sanchez, B; Guasch, A; Bogonez, P; Galvez, C; Puig, V; Prat, C; Semino, C E; Bayes-Genis, A; Bragos, R

    2012-01-01

    The human heart tissue has a limited capacity for regeneration. Tissue and cellular therapies based on the use of stem cells may be useful alternatives to limit the size of myocardial infarction. In this paper, the preliminary results from an experimental campaign for on-line monitoring of myocardium scar infarction are presented. This study has been carried out under a research project that has as main objective the development and application of a bioactive patch implant for regeneration of myocardial infarction. Electrical Impedance Spectroscopy (EIS) has been chosen as a tissue state monitoring technique. What is presented in this communication is the first results of an implantable EIS measurement system which has been implanted in a subset of the animals corresponding to the control group, along one month. In all the animals, the myocardial infarction was induced by the ligation of the first circumflex marginal artery. In the animal group presented, the bioactive patch scaffold and the electrodes were implanted without the stem cells load. The scaffold is a piece of decellularized human pericardium, lyophilized and rehydrated with hydrogel RAD16-I. Nanogold particles were also placed near the electrodes to improve the electrode area conductivity. The results presented correspond to the subset of animals (n = 5), which had implanted the bioimpedance system monitoring the electrical impedance spectrum in vivo during 1 month. Two electrodes were connected to the bioactive patch implant. A total of 14 logarithmically spaced frequencies were measured every 5 minutes, from 100 Hz to 200 kHz. Results show a convergence of low-frequency and high frequency impedance magnitudes along the measurement period, which is coherent with the scar formation.

  4. 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.

  5. Calibration-free electrical conductivity measurements for highly conductive slags

    SciTech Connect

    MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

    2000-05-01

    This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

  6. Electric impedance platelet aggregometry in cardiac surgery patients: A comparative study of two technologies.

    PubMed

    Ranucci, Marco; Baryshnikova, Ekaterina; Crapelli, Giulia Beatrice; Ranucci, Matteo; Meloni, Silvia; Pistuddi, Valeria

    2016-01-01

    Platelet function tests are suggested to assess platelet reactivity before cardiac and major non-cardiac surgery. Different point-of-care platelet function tests are available. Among these, electric impedance platelet aggregometry (EIPA) (Multiplate®, MP) is one of the most widely used techniques. Recently, a new EIPA system (Rotem Platelet®, RP) was released. This is a comparative study of platelet function measured with MP and RP. Fifty cardiac surgery patients were admitted to this study. All the patients received a preoperative platelet function test with both the MP and the RP; for each technology, two tests were performed: the ADPtest (investigating P2Y12 receptor platelet reactivity) and the TRAPtest (investigating the thrombin-dependent platelet reactivity). ADP-based platelet reactivity values demonstrated a significant (p = 0.019) correlation between the MP and the RP; and a marginally significant (p = 0.042) correlation for TRAP-based tests. The Bland-Altman analysis of the ADPtest demonstrated a positive bias of 5.94 units (MP > RP) and a percentage error of 88%. For the TRAPtest, there was a positive bias of 12 units (MP > RP) and a percentage error of 89%. In patients who were preoperatively treated with P2Y12 receptor inhibitors, only the MP ADPtest was positively associated with the days from drug discontinuation (p = 0.003). Platelet function assessment with RP greatly differs from the equivalent MP measure, and no correction value can be applied due to the low level of precision. This applies both to ADPtest and TRAPtest. The MP ADPtest is more reliable for platelet reactivity after discontinuation of P2Y12 receptor inhibitors.

  7. Signal-to-Noise Ratio Analysis of a Phase-Sensitive Voltmeter for Electrical Impedance Tomography.

    PubMed

    Murphy, Ethan K; Takhti, Mohammad; Skinner, Joseph; Halter, Ryan J; Odame, Kofi

    2017-04-01

    In this paper, thorough analysis along with mathematical derivations of the matched filter for a voltmeter used in electrical impedance tomography systems are presented. The effect of the random noise in the system prior to the matched filter, generated by other components, are considered. Employing the presented equations allow system/circuit designers to find the maximum tolerable noise prior to the matched filter that leads to the target signal-to-noise ratio (SNR) of the voltmeter, without having to over-design internal components. A practical model was developed that should fall within 2 dB and 5 dB of the median SNR measurements of signal amplitude and phase, respectively. In order to validate our claims, simulation and experimental measurements have been performed with an analog-to-digital converter (ADC) followed by a digital matched filter, while the noise of the whole system was modeled as the input referred at the ADC input. The input signal was contaminated by a known value of additive white Gaussian noise (AWGN) noise, and the noise level was swept from 3% to 75% of the least significant bit (LSB) of the ADC. Differences between experimental and both simulated and analytical SNR values were less than 0.59 and 0.35 dB for RMS values ≥ 20% of an LSB and less than 1.45 and 2.58 dB for RMS values < 20% of an LSB for the amplitude and phase, respectively. Overall, this study provides a practical model for circuit designers in EIT, and a more accurate error analysis that was previously missing in EIT literature.

  8. Classification of thyroid nodules using a resonance-frequency-based electrical impedance spectroscopy: progress assessment

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    The incidence of thyroid cancer is rising faster than other malignancies and has nearly doubled in the United States (U.S.) in the last 30 years. However, classifying between malignant and benign thyroid nodules is often difficult. Although ultrasound guided Fine Needle Aspiration Biopsy (FNAB) is considered an excellent tool for triaging patients, up to 25% of FNABs are inconclusive. As a result, definitive diagnosis requires an exploratory surgery and a large number of these are performed in the U.S. annually. It would be extremely beneficial to develop a non-invasive tool or procedure that could assist in assessing the likelihood of malignancy of otherwise indeterminate thyroid nodules, thereby reducing the number of exploratory thyroidectomies that are performed under general anesthesia. In this preliminary study we demonstrate a unique hand-held Resonance-frequency based Electrical Impedance Spectroscopy (REIS) device with six pairs of detection probes to detect and classify thyroid nodules using multi-channel EIS output signal sweeps. Under an Institutional Review Board (IRB)-approved case collection protocol, this REIS device is being tested in our clinical facility and we have been collecting an initial patient data set since March of this year. Between March and August of 2011, 65 EIS tests were conducted on 65 patients. Among these cases, six depicted pathology-verified malignant cells. Our initial assessment indicates the feasibility of easily applying this REIS device and measurement approach in a very busy clinical setting. The measured resonance frequency differences between malignant and benign nodules could potentially make it possible to accurately classify indeterminate thyroid nodules.

  9. Static resistivity image of a cubic saline phantom in magnetic resonance electrical impedance tomography (MREIT).

    PubMed

    Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyeong; Kwon, Ohin; Seo, Jin Keun; Baek, Woon Sik

    2003-05-01

    In magnetic resonance electrical impedance tomography (MREIT) we inject currents through electrodes placed on the surface of a subject and try to reconstruct cross-sectional resistivity (or conductivity) images using internal magnetic flux density as well as boundary voltage measurements. In this paper we present a static resistivity image of a cubic saline phantom (50 x 50 x 50 mm3) containing a cylindrical sausage object with an average resistivity value of 123.7 ohms cm. Our current MREIT system is based on an experimental 0.3 T MRI scanner and a current injection apparatus. We captured MR phase images of the phantom while injecting currents of 28 mA through two pairs of surface electrodes. We computed current density images from magnetic flux density images that are proportional to the MR phase images. From the current density images and boundary voltage data we reconstructed a cross-sectional resistivity image within a central region of 38.5 x 38.5 mm2 at the middle of the phantom using the J-substitution algorithm. The spatial resolution of the reconstructed image was 64 x 64 and the reconstructed average resistivity of the sausage was 117.7 ohms cm. Even though the error in the reconstructed average resistivity value was small, the relative L2-error of the reconstructed image was 25.5% due to the noise in measured MR phase images. We expect improvements in the accuracy by utilizing an MRI scanner with higher SNR and increasing the size of voxels scarifying the spatial resolution.

  10. Effects of metoclopramide on gastric motility measured by short-term bio-impedance

    PubMed Central

    Huerta-Franco, María-Raquel; Vargas-Luna, Miguel; Capaccione, Kathleen M; Yañez-Roldán, Etna; Hernández-Ledezma, Ulises; Morales-Mata, Ismael; Córdova-Fraga, Teodoro

    2009-01-01

    AIM: To analyze the accuracy of short-term bio-impedance as a means of measuring gastric motility. METHODS: We evaluated differences in the short-term electrical bio-impedance signal from the gastric region in the following conditions: (1) fasting state, (2) after the administration of metoclopramide (a drug that induces an increase in gastric motility) and (3) after food ingestion in 23 healthy volunteers. We recorded the real component of the electrical impedance signal from the gastric region for 1000 s. We performed a Fast Fourier Transform (FFT) on this data and then compared the signal among the fasting, medicated, and postprandial conditions using the median of the area under the curve, the relative area under the curve and the main peak activity. RESULTS: The median of the area under the curve of the frequency range in the region between 2-8 cycles per minute (cpm) decreased from 4.7 cpm in the fasting condition to 4.0 cpm in the medicated state (t = 3.32, P = 0.004). This concurred with the decrease seen in the relative area under the FFT curve in the region from 4 to 8 cpm from 38.3% to 26.6% (t = 2.81, P = 0.012) and the increase in area in the region from 2 to 4 cpm from 22.4% to 27.7%, respectively (t = -2.5, P = 0.022). Finally the main peak position also decreased in the region from 2 to 8 cpm. Main peak activity in the fasting state was 4.72 cpm and declined to 3.45 cpm in the medicated state (t = 2.47, P = 0.025). There was a decrease from the fasting state to the postprandial state at 3.02 cpm (t = 4.0, P = 0.0013). CONCLUSION: Short-term electrical bio-impedance can assess gastric motility changes in individuals experiencing gastric stress by analyzing the area medians and relative areas under the FFT curve. PMID:19824108

  11. Detailed electrical measurements on sago starch biopolymer solid electrolyte

    NASA Astrophysics Data System (ADS)

    Singh, Rahul; Baghel, Jaya; Shukla, S.; Bhattacharya, B.; Rhee, Hee-Woo; Singh, Pramod K.

    2014-12-01

    The biopolymer solid electrolyte has been synthesized and characterized. Potassium iodide (KI) has been added in polymer matrix to develop solid polymer electrolyte. Relationships between electrical, ionic transport parameter and mechanism have been studied in detail. Impedance spectroscopy reveals the detailed electrical studies and ion transport mechanism. The ion dissociation factor is compared with a measured dielectric constant at a fixed frequency. The dielectric data are calculated which support the ionic conductivity data.

  12. Improvement of Depth Profiling into Biotissues Using Micro Electrical Impedance Spectroscopy on a Needle with Selective Passivation

    PubMed Central

    Yun, Joho; Kim, Hyeon Woo; Lee, Jong-Hyun

    2016-01-01

    A micro electrical impedance spectroscopy (EIS)-on-a-needle for depth profiling (μEoN-DP) with a selective passivation layer (SPL) on a hypodermic needle was recently fabricated to measure the electrical impedance of biotissues along with the penetration depths. The SPL of the μEoN-DP enabled the sensing interdigitated electrodes (IDEs) to contribute predominantly to the measurement by reducing the relative influence of the connection lines on the sensor output. The discrimination capability of the μEoN-DP was verified using phosphate-buffered saline (PBS) at various concentration levels. The resistance and capacitance extracted through curve fitting were similar to those theoretically estimated based on the mixing ratio of PBS and deionized water; the maximum discrepancies were 8.02% and 1.85%, respectively. Depth profiling was conducted using four-layered porcine tissue to verify the effectiveness of the discrimination capability of the μEoN-DP. The magnitude and phase between dissimilar porcine tissues (fat and muscle) were clearly discriminated at the optimal frequency of 1 MHz. Two kinds of simulations, one with SPL and the other with complete passivation layer (CPL), were performed, and it was verified that the SPL was advantageous over CPL in the discrimination of biotissues in terms of sensor output. PMID:28009845

  13. Measuring impedance in congestive heart failure: Current options and clinical applications

    PubMed Central

    Tang, W. H. Wilson; Tong, Wilson

    2011-01-01

    Measurement of impedance is becoming increasingly available in the clinical setting as a tool for assessing hemodynamics and volume status in patients with heart failure. The 2 major categories of impedance assessment are the band electrode method and the implanted device lead method. The exact sources of the impedance signal are complex and can be influenced by physiologic effects such as blood volume, fluid, and positioning. This article provides a critical review of our current understanding and promises of impedance measurements, the techniques that have evolved, as well as the evidence and limitations regarding their clinical applications in the setting of heart failure management. PMID:19249408

  14. Overview Of Impedance Sensors

    NASA Astrophysics Data System (ADS)

    Abele, John E.

    1989-08-01

    Electrical impedance has been one of the many "tools of great promise" that physicians have employed in their quest to measure and/or monitor body function or physiologic events. So far, the expectations for its success have always exceeded its performance. In simplistic terms, physiologic impedance is a measure of the resistance in the volume between electrodes which changes as a function of changes in that volume, the relative impedance of that volume, or a combination of these two. The history and principles of electrical impedance are very nicely reviewed by Geddes and Baker in their textbook "Principles of Applied Biomedical Instrumentation". It is humbling, however, to note that Cremer recorded variations in electrical impedance in frog hearts as early as 1907. The list of potential applications includes the measurement of thyroid function, estrogen activity, galvanic skin reflex, respiration, blood flow by conductivity dilution, nervous activity and eye movement. Commercial devices employing impedance have been and are being used to measure respiration (pneumographs and apneamonitors), pulse volume (impedance phlebographs) and even noninvasive cardiac output.

  15. Electric impedance sensing in cell-substrates for rapid and selective multipotential differentiation capacity monitoring of human mesenchymal stem cells.

    PubMed

    Reitinger, Stephan; Wissenwasser, Jürgen; Kapferer, Werner; Heer, Rudolf; Lepperdinger, Günter

    2012-04-15

    Biosensor systems which enable impedance measurements on adherent cell layers under label-free conditions are considered powerful tools for monitoring specific biological characteristics. A radio frequency identification-based sensor platform was adopted to characterize cultivation and differentiation of human bone marrow-derived multipotent stem cells (bmMSC) over periods of up to several days and weeks. Electric cell-substrate impedance sensing was achieved through fabrication of sensitive elements onto glass substrates which comprised two comb-shaped interdigitated gold electrodes covering an area of 1.8 mm×2 mm. The sensing systems were placed into the wells of a 6-well tissue culture plate, stacked onto a reader unit and could thus be handled and operated under sterile conditions. Continuous measurements were carried out with a sinusoidal voltage of 35 mV at a frequency of 10 kHz. After seeding of human bmMSC, this sensor was able to trace significant impedance changes contingent upon cell spreading and adhesion. The re-usable system was further proven suitable for live examination of cell-substrate attachment or continuous cell monitoring up to several weeks. Induction of either osteogenic or adipogenic differentiation could be validated in bmMSC cultures within a few days, in contrast to state-of-the-art protocols, which require several weeks of cultivation time. In the context of medical cell production in a GMP-compliant process, the here presented interdigitated electric microsensor technology allows the documentation of MSC quality in a fast, efficient and reliable fashion.

  16. Identification of fluids and an interface between fluids by measuring complex impedance

    DOEpatents

    Lee, David O.; Wayland, Jr., James R.

    1989-01-01

    Complex impedance measured over a predefined frequency range is used to determine the identity of different oils in a column. The location of an interface between the oils is determined from the percent frequency effects of the complex impedance measured across the interface.

  17. Identification of fluids and an interface between fluids by measuring complex impedance

    DOEpatents

    Lee, D.O.; Wayland, J.R. Jr.

    1989-12-05

    Complex impedance measured over a predefined frequency range is used to determine the identity of different oils in a column. The location of an interface between the oils is determined from the percent frequency effects of the complex impedance measured across the interface. 5 figs.

  18. High frequency electromagnetic impedance measurements for characterization, monitoring and verification efforts. 1998 annual progress report

    SciTech Connect

    Lee, K.H.; Pellerin, L.; Becker, A.

    1998-06-01

    'Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small due, and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. The authors are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach, known as the magnetotelluric (MT) method at low frequencies. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques. The summary of the work to date is divided into three sections: equipment procurement, instrumentation, and theoretical developments. For most earth materials, the frequency range from 1 to 100 MHz encompasses a very difficult transition zone between the wave propagation of displacement currents and the diffusive behavior of conduction currents. Test equipment, such as signal generators and amplifiers, does not cover the entire range except at great expense. Hence the authors have divided the range of investigation into three sub-ranges: 1--10 MHz, 10--30 MHz, and 30--100 MHz. Results to date are in the lowest frequency range of 1--10 MHz. Even though conduction currents

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

    PubMed

    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.

  20. Utilization of Electrical Impedance Tomography to Detect Internal Anomalies in Southern Pine Logs

    NASA Astrophysics Data System (ADS)

    Steele, Philip; Cooper, Jerome

    2006-03-01

    A large body of research has shown that knowledge of internal defect location in logs prior to sawing has the potential to significantly increase lumber value yield. This paper describes a relatively low-capital log scanning technique based on Electrical Impedance Tomography (EIT) to image anomalies interior to sawlogs. Static testing results showed that knots, juvenile and compression wood internal to logs can be detected. Although resolution is lower than that of CT and NMR technologies, the low cost of this EIT application should render it competitive.

  1. 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.

  2. Evaluation for Electrochemical Impedance Measurement of Carbon Nanotube Taste Sensor

    NASA Astrophysics Data System (ADS)

    Takeda, Naoki; Hirata, Takamichi; Akiya, Masahiro

    In our laboratory, a nano-bio taste sensor based on carbon nanotubes has been developed. However, previous technique cannot separate elements such as CNT random network or electrode surface etc., because of sensor impedance change in fixed frequency. Electrochemical impedance spectroscopy (EIS) revealed CNT taste sensor with two R/C parallel circuits. Experimental complex plane plots were reproduced using a computer simulation program based upon the lumped equivalent circuit approach. It was found that the sensor has two relaxation times, and also that these circuits consist of two elements such as electrode surface and CNT random network.

  3. Monitoring of regional lung ventilation using electrical impedance tomography after cardiac surgery in infants and children.

    PubMed

    Krause, Ulrich; Becker, Kristin; Hahn, Günter; Dittmar, Jörg; Ruschewski, Wolfgang; Paul, Thomas

    2014-08-01

    Electrical impedance tomography (EIT) is a noninvasive method to monitor regional lung ventilation in infants and children without using radiation. The objective of this prospective study was to determine the value of EIT as an additional monitoring tool to assess regional lung ventilation after pediatric cardiac surgery for congenital heart disease in infants and children. EIT monitoring was performed in a prospective study comprising 30 pediatric patients who were mechanically ventilated after cardiac surgery. Data were analyzed off-line with respect to regional lung ventilation in different clinical situations. EIT data were correlated with respirator settings and arterial carbon dioxide (CO2) partial pressure in the blood. In 29 of 30 patients, regional ventilation of the lung could sufficiently and reliably be monitored by means of EIT. The effects of the transition from mechanical ventilation to spontaneous breathing after extubation on regional lung ventilation were studied. After extubation, a significant decrease of relative impedance changes was evident. In addition, a negative correlation of arterial CO2 partial pressure and relative impedance changes could be shown. EIT was sufficient to discriminate differences of regional lung ventilation in children and adolescents after cardiac surgery. EIT reliably provided additional information on regional lung ventilation in children after cardiac surgery. Neither chest tubes nor pacemaker wires nor the intensive care unit environment interfered with the application of EIT. EIT therefore may be used as an additional real-time monitoring tool in pediatric cardiac intensive care because it is noninvasive.

  4. Intracellular Impedance Measurements Reveal Non-ohmic Properties of the Extracellular Medium around Neurons

    PubMed Central

    Gomes, Jean-Marie; Bédard, Claude; Valtcheva, Silvana; Nelson, Matthew; Khokhlova, Vitalia; Pouget, Pierre; Venance, Laurent; Bal, Thierry; Destexhe, Alain

    2016-01-01

    Determining the electrical properties of the extracellular space around neurons is important for understanding the genesis of extracellular potentials, as well as for localizing neuronal activity from extracellular recordings. However, the exact nature of these extracellular properties is still uncertain. Here, we introduce a method to measure the impedance of the tissue, one that preserves the intact cell-medium interface using whole-cell patch-clamp recordings in vivo and in vitro. We find that neural tissue has marked non-ohmic and frequency-filtering properties, which are not consistent with a resistive (ohmic) medium, as often assumed. The amplitude and phase profiles of the measured impedance are consistent with the contribution of ionic diffusion. We also show that the impact of such frequency-filtering properties is possibly important on the genesis of local field potentials, as well as on the cable properties of neurons. These results show non-ohmic properties of the extracellular medium around neurons, and suggest that source estimation methods, as well as the cable properties of neurons, which all assume ohmic extracellular medium, may need to be reevaluated. PMID:26745426

  5. Sensor Applications of Soft Magnetic Materials Based on Magneto-Impedance, Magneto-Elastic Resonance and Magneto-Electricity

    PubMed Central

    García-Arribas, Alfredo; Gutiérrez, Jon; Kurlyandskaya, Galina V.; Barandiarán, José M.; Svalov, Andrey; Fernández, Eduardo; Lasheras, Andoni; de Cos, David; Bravo-Imaz, Iñaki

    2014-01-01

    The outstanding properties of selected soft magnetic materials make them successful candidates for building high performance sensors. In this paper we present our recent work regarding different sensing technologies based on the coupling of the magnetic properties of soft magnetic materials with their electric or elastic properties. In first place we report the influence on the magneto-impedance response of the thickness of Permalloy films in multilayer-sandwiched structures. An impedance change of 270% was found in the best conditions upon the application of magnetic field, with a low field sensitivity of 140%/Oe. Second, the magneto-elastic resonance of amorphous ribbons is used to demonstrate the possibility of sensitively measuring the viscosity of fluids, aimed to develop an on-line and real-time sensor capable of assessing the state of degradation of lubricant oils in machinery. A novel analysis method is shown to sensitively reveal the changes of the damping parameter of the magnetoelastic oscillations at the resonance as a function of the oil viscosity. Finally, the properties and performance of magneto-electric laminated composites of amorphous magnetic ribbons and piezoelectric polymer films are investigated, demonstrating magnetic field detection capabilities below 2.7 nT. PMID:24776934

  6. A quantitative cell modeling and wound-healing analysis based on the Electric Cell-substrate Impedance Sensing (ECIS) method.

    PubMed

    Yang, Jen Ming; Chen, Szi-Wen; Yang, Jhe-Hao; Hsu, Chih-Chin; Wang, Jong-Shyan

    2016-02-01

    In this paper, a quantitative modeling and wound-healing analysis of fibroblast and human keratinocyte cells is presented. Our study was conducted using a continuous cellular impedance monitoring technique, dubbed Electric Cell-substrate Impedance Sensing (ECIS). In fact, we have constructed a mathematical model for quantitatively analyzing the cultured cell growth using the time series data directly derived by ECIS in a previous work. In this study, the applicability of our model into the keratinocyte cell growth modeling analysis was assessed first. In addition, an electrical "wound-healing" assay was used as a means to evaluate the healing process of keratinocyte cells at a variety of pressures. Two innovative and new-defined indicators, dubbed cell power and cell electroactivity, respectively, were developed for quantitatively characterizing the biophysical behavior of cells. We then employed the wavelet transform method to perform a multi-scale analysis so the cell power and cell electroactivity across multiple observational time scales may be captured. Numerical results indicated that our model can well fit the data measured from the keratinocyte cell culture for cell growth modeling analysis. Also, the results produced by our quantitative analysis showed that the wound healing process was the fastest at the negative pressure of 125mmHg, which consistently agreed with the qualitative analysis results reported in previous works.

  7. An approach to fouling characterization of an ion-exchange membrane using current-voltage relation and electrical impedance spectroscopy.

    PubMed

    Park, Jin-Soo; Choi, Jae-Hwan; Yeon, Kyeong-Ho; Moon, Seung-Hyeon

    2006-02-01

    Fouling phenomena of an anion-exchange membrane by bovine serum albumin (BSA) were investigated using current-voltage relation and electrical impedance spectroscopy (EIS) in this study. Electrochemical parameters of the Neosepta CMX cation- and AMX anion-exchange membrane (Tokuyama Corp., Japan) such as limiting current density (LCD), transport number, plateau length, and fraction of the conducting phase were measured. Fraction of the conducting phase of the ion-exchange membranes, calculated from the modified Sand equation, played an important role in determining the electrochemical parameters in the presence of foulants such as BSA. Fraction of the conducting phase of the AMX membrane significantly decreased in the presence of BSA. Two distinguishable slopes were observed in the over-LCD region of the current-voltage (I-V) curve, indicating the change of resistance. To further elucidate the phenomena, the electrical impedance spectroscopic study was carried out using the offset alternating current. It was found that the negatively charged loose fouling layer changed to the dense deposited BSA on the surface of the AMX membrane occurring along with enhanced water dissociation phenomena at the surface of the fouled AMX membrane at a higher current density. This result was confirmed by water dissociation experiments in a six-compartment electrodialysis cell.

  8. Highly sensitive three-dimensional interdigitated microelectrode for microparticle detection using electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Chang, Fu-Yu; Chen, Ming-Kun; Wang, Min-Haw; Jang, Ling-Sheng

    2016-02-01

    Cell impedance analysis is widely used for monitoring biological and medical reactions. In this study, a highly sensitive three-dimensional (3D) interdigitated microelectrode (IME) with a high aspect ratio on a polyimide (PI) flexible substrate was fabricated for microparticle detection (e.g. cell quantity detection) using electroforming and lithography technology. 3D finite element simulations were performed to compare the performance of the 3D IME (in terms of sensitivity and signal-to-noise ratio) to that of a planar IME for particles in the sensing area. Various quantities of particles were captured in Dulbecco’s modified Eagle medium and their impedances were measured. With the 3D IME, the particles were arranged in the gap, not on the electrode, avoiding the noise due to particle position. For the maximum particle quantities, the results show that the 3D IME has at least 5-fold higher sensitivity than that of the planar IME. The trends of impedance magnitude and phase due to particle quantity were verified using the equivalent circuit model. The impedance (1269 Ω) of 69 particles was used to estimate the particle quantity (68 particles) with 98.6% accuracy using a parabolic regression curve at 500 kHz.

  9. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch.

    PubMed

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H W

    2015-10-23

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves.

  10. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch

    PubMed Central

    Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H. W.

    2015-01-01

    In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

  11. Electron density dependence of impedance probe plasma potential measurements

    SciTech Connect

    Walker, D. N.; Blackwell, D. D.; Amatucci, W. E.

    2015-08-15

    In earlier works, we used spheres of various sizes as impedance probes in demonstrating a method of determining plasma potential, φ{sub p}, when the probe radius is much larger than the Debye length, λ{sub D}. The basis of the method in those works [Walker et al., Phys. Plasmas 13, 032108 (2006); ibid. 15, 123506 (2008); ibid. 17, 113503 (2010)] relies on applying a small amplitude signal of fixed frequency to a probe in a plasma and, through network analyzer-based measurements, determining the complex reflection coefficient, Γ, for varying probe bias, V{sub b}. The frequency range of the applied signal is restricted to avoid sheath resonant effects and ion contributions such that ω{sub pi} ≪ ω ≪ ω{sub pe}, where ω{sub pi} is the ion plasma frequency and ω{sub pe} is the electron plasma frequency. For a given frequency and applied bias, both Re(Z{sub ac}) and Im(Z{sub ac}) are available from Γ. When Re(Z{sub ac}) is plotted versus V{sub b}, a minimum predicted by theory occurs at φ{sub p} [Walker et al., Phys. Plasmas 17, 113503 (2010)]. In addition, Im(Z{sub ac}) appears at, or very near, a maximum at φ{sub p}. As n{sub e} decreases and the sheath expands, the minimum becomes harder to discern. The purpose of this work is to demonstrate that when using network analyzer-based measurements, Γ itself and Im(Z{sub ac}) and their derivatives are useful as accompanying indicators to Re(Z{sub ac}) in these difficult cases. We note the difficulties encountered by the most commonly used plasma diagnostic, the Langmuir probe. Spherical probe data is mainly used in this work, although we present limited data for a cylinder and a disk. To demonstrate the effect of lowered density as a function of probe geometry, we compare the cylinder and disk using only the indicator Re(Z{sub ac})

  12. 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.

  13. A real time affinity biosensor on an insulated polymer using electric impedance spectroscopy in dielectric microchips.

    PubMed

    Kechadi, Mohammed; Sotta, Bruno; Chaal, Lila; Tribollet, Bernard; Gamby, Jean

    2014-06-21

    This paper presents development of real time monitoring of binding events on flexible plastic in microchips. Two planar carbon microelectrodes are integrated into an insulated polyethylene terephthalate microchip without direct electrical contact with the solution in the microchannel. It has been possible to probe the electric impedance changes through the interface constituted by the microelectrode/PET microchannel/solution when a biomolecular interaction takes place on the polymer surface. This new transduction for biosensing was demonstrated for the molecular recognition of BSA immobilized on the polymer microchannel surface using the corresponding rabbit anti-BSA antibodies as an analyte in the flow microchannel at the nanomolar range concentration. The equilibrium association constant was determined for the affinity reaction between both ligands and was obtained equal to 5 × 10(7) M(-1). The promising results obtained with this new device make it a competitive biosensor.

  14. 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.

  15. Micro electrical impedance spectroscopy on a needle for ex vivo discrimination between human normal and cancer renal tissues.

    PubMed

    Yun, Joho; Kim, Hyeon Woo; Park, Yangkyu; Cha, Jung-Joon; Lee, Jeong Zoo; Shin, Dong Gil; Lee, Jong-Hyun

    2016-05-01

    The ex-vivo discrimination between human normal and cancer renal tissues was confirmed using μEoN (micro electrical impedance spectroscopy-on-a-needle) by measuring and comparing the electrical impedances in the frequency domain. To quantify the extent of discrimination between dissimilar tissues and to determine the optimal frequency at which the discrimination capability is at a maximum, discrimination index (DI) was employed for both magnitude and phase. The highest values of DI for the magnitude and phase were 5.15 at 1 MHz and 3.57 at 1 kHz, respectively. The mean magnitude and phase measured at the optimal frequency for normal tissues were 5013.40 ± 94.39 Ω and -68.54 ± 0.72°, respectively; those for cancer tissues were 4165.19 ± 70.32 Ω and -64.10 ± 0.52°, respectively. A statistically significant difference (p< 0.05) between the two tissues was observed at all the investigated frequencies. To extract the electrical properties (resistance and capacitance) of these bio-tissues through curve fitting with experimental results, an equivalent circuit was proposed based on the μEoN structure on the condition that the μEoN was immersed in the bio-tissues. The average and standard deviation of the extracted resistance and capacitance for the normal tissues were 6.22 ± 0.24 kΩ and 280.21 ± 32.25 pF, respectively, and those for the cancer tissues were 5.45 ± 0.22 kΩ and 376.32 ± 34.14 pF, respectively. The electrical impedance was higher in the normal tissues compared with the cancer tissues. The μEoN could clearly discriminate between normal and cancer tissues by comparing the results at the optimal frequency (magnitude and phase) and those of the curve fitting (extracted resistance and capacitance).

  16. In situ characterization of fouling in reverse osmosis membranes using electrical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Chilcott, Terry; Antony, Alice; Coster, Hans; Leslie, Greg

    2013-04-01

    Analytical solutions of the Nernst-Planck, Poisson and continuity equations for a membrane undergoing reverse osmosis in a cross-flow system reveal that the flow of alternating ionic charge induced in the membrane during impedance measurements is actively assisted by the flow of water. The actively driven current manifested "inductive" responses in impedance measurements of a Filmtec BW30 reverse osmosis membrane mounted in an Inphaze flat-bed cross-flow module after 16 hours of filtering a mineral salt solution seeded with CaCl2 and NaHCO3 at pressure of 900 kPa. Fitted transfer functions resolved conduction and capacitive properties of four membrane layers, diffusion/concentration phenomenon and a pseudo "inductor" shunted by a conductor. A 10-fold decrease in the shunt conductance correlated with smaller increases in the conductance values for the filtrate and membranous layers, and the onset of fouling diagnosed by a rapid increase in flux decline.

  17. Nondestructive Determination of Moisture Content in Dry Fruits by Impedance and Phase angle measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Impedance (Z), and phase angle (') of a cylindrical parallel-plate capacitor with dry fruits between the plates was measured using a CI meter (Chari’s Impedance meter), at 1 and 9 MHz . Capacitance, C was derived from Z and ', and using the C, ', and Z values of a set of cherries whose moisture con...

  18. FPGA Based High Speed Data Acquisition System for Electrical Impedance Tomography.

    PubMed

    Khan, S; Borsic, A; Manwaring, Preston; Hartov, Alexander; Halter, Ryan

    2013-03-01

    Electrical Impedance Tomography (EIT) systems are used to image tissue bio-impedance. EIT provides a number of features making it attractive for use as a medical imaging device including the ability to image fast physiological processes (>60 Hz), to meet a range of clinical imaging needs through varying electrode geometries and configurations, to impart only non-ionizing radiation to a patient, and to map the significant electrical property contrasts present between numerous benign and pathological tissues. To leverage these potential advantages for medical imaging, we developed a modular 32 channel data acquisition (DAQ) system using National Instruments' PXI chassis, along with FPGA, ADC, Signal Generator and Timing and Synchronization modules. To achieve high frame rates, signal demodulation and spectral characteristics of higher order harmonics were computed using dedicated FFT-hardware built into the FPGA module. By offloading the computing onto FPGA, we were able to achieve a reduction in throughput required between the FPGA and PC by a factor of 32:1. A custom designed analog front end (AFE) was used to interface electrodes with our system. Our system is wideband, and capable of acquiring data for input signal frequencies ranging from 100 Hz to 12 MHz. The modular design of both the hardware and software will allow this system to be flexibly configured for the particular clinical application.

  19. FPGA Based High Speed Data Acquisition System for Electrical Impedance Tomography

    PubMed Central

    Khan, S; Borsic, A; Manwaring, Preston; Hartov, Alexander; Halter, Ryan

    2014-01-01

    Electrical Impedance Tomography (EIT) systems are used to image tissue bio-impedance. EIT provides a number of features making it attractive for use as a medical imaging device including the ability to image fast physiological processes (>60 Hz), to meet a range of clinical imaging needs through varying electrode geometries and configurations, to impart only non-ionizing radiation to a patient, and to map the significant electrical property contrasts present between numerous benign and pathological tissues. To leverage these potential advantages for medical imaging, we developed a modular 32 channel data acquisition (DAQ) system using National Instruments’ PXI chassis, along with FPGA, ADC, Signal Generator and Timing and Synchronization modules. To achieve high frame rates, signal demodulation and spectral characteristics of higher order harmonics were computed using dedicated FFT-hardware built into the FPGA module. By offloading the computing onto FPGA, we were able to achieve a reduction in throughput required between the FPGA and PC by a factor of 32:1. A custom designed analog front end (AFE) was used to interface electrodes with our system. Our system is wideband, and capable of acquiring data for input signal frequencies ranging from 100 Hz to 12 MHz. The modular design of both the hardware and software will allow this system to be flexibly configured for the particular clinical application. PMID:24729790

  20. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  1. The time taken for the regional distribution of ventilation to stabilise: an investigation using electrical impedance tomography.

    PubMed

    Caruana, L; Paratz, J D; Chang, A; Barnett, A G; Fraser, J F

    2015-01-01

    Electrical impedance tomography is a novel technology capable of quantifying ventilation distribution in the lung in real time during various therapeutic manoeuvres. The technique requires changes to the patient's position to place the electrical impedance tomography electrodes circumferentially around the thorax. The impact of these position changes on the time taken to stabilise the regional distribution of ventilation determined by electrical impedance tomography is unknown. This study aimed to determine the time taken for the regional distribution of ventilation determined by electrical impedance tomography to stabilise after changing position. Eight healthy, male volunteers were connected to electrical impedance tomography and a pneumotachometer. After 30 minutes stabilisation supine, participants were moved into 60 degrees Fowler's position and then returned to supine. Thirty minutes was spent in each position. Concurrent readings of ventilation distribution and tidal volumes were taken every five minutes. A mixed regression model with a random intercept was used to compare the positions and changes over time. The anterior-posterior distribution stabilised after ten minutes in Fowler's position and ten minutes after returning to supine. Left-right stabilisation was achieved after 15 minutes in Fowler's position and supine. A minimum of 15 minutes of stabilisation should be allowed for spontaneously breathing individuals when assessing ventilation distribution. This time allows stabilisation to occur in the anterior-posterior direction as well as the left-right direction.

  2. Local transverse coupling impedance measurements in a synchrotron light source from turn-by-turn acquisitions

    NASA Astrophysics Data System (ADS)

    Carlà, Michele; Benedetti, Gabriele; Günzel, Thomas; Iriso, Ubaldo; Martí, Zeus

    2016-12-01

    Transverse beam coupling impedance is a source of beam instabilities that limits the machine performance in circular accelerators. Several beam based techniques have been used to measure the transverse impedance of an accelerator, usually based on the optics distortion produced by the impedance source itself. Beam position monitor turn-by-turn analysis for impedance characterization has been usually employed in large circumference machines, while synchrotron light sources have mainly used slow orbit based techniques. Instead, the work presented in this paper uses for the first time turn-by-turn data at ALBA to advance the measurement technique into the range of the typically small impedance values of modern light sources. We have measured local impedance contributions through the observation of phase advance versus bunch charge using the betatron oscillations excited with a fast dipole kicker. The ALBA beam position monitor system and the precision of the turn-by-turn analysis allowed to characterize the main sources of transverse impedance, in good agreement with the model values, including the impedance of an in-vacuum undulator.

  3. Anisotropy of human muscle via non invasive impedance measurements. Frequency dependence of the impedance changes during isometric contractions

    NASA Astrophysics Data System (ADS)

    Kashuri, Hektor

    In this thesis we present non invasive muscle impedance measurements using rotatable probes extending the work done by Aaron et al. (1997) by measuring not only the real part of the impedance but the imaginary part as well. The results reveal orientations of underlying muscle fibers via minima in resistance and reactance versus angle curves, suggesting this method as potentially useful for studying muscle properties in clinical and physiological research. Calculations of the current distribution for a slab of material with anisotropic conductivity show that the current distribution depends strongly on the separation of two current electrodes and as well as on its conducting anisotropy. Forearm muscle impedance measurements at 50 kHz done by Shiffman et al. (2003) had shown that both resistance (R) and reactance (X) increase during isometric contraction. We have extended these measurements in the 3 to 100 kHz range and we found that resistance (R) and reactance (X) both increase and their changes increased or decreased at frequency dependent rates. Analysis based on circuit models of changes in R and X during the short contraction pulses showed that the extra cellular fluid resistance increased by 3.9 +/- 1.4 %, while the capacitance increased by 5.6 +/- 2 %. For long contraction pulses at very low frequencies: (1) there was practically no change in R during contraction, which implies that these changes are due to cellular membrane or intracellular effects with the extra cellular water component not participating, and (2) in post contraction stage there were no morphological changes which means that drifts in R can only be due to physiological changes. Following Shiffman et al. (2003) we measured impedance changes of R and X during a triangular shaped pulse of force generated via isometric forearm muscle contraction at 50 kHz. We measured these changes in 3-100 kHz frequency range for a stair case pulse of forces and the results showed that they are frequency

  4. In situ measurement of tissue impedance using an inductive coupling interface circuit.

    PubMed

    Chiu, Hung-Wei; Chuang, Jia-min; Lu, Chien-Chi; Lin, Wei-Tso; Lin, Chii-Wann; Lin, Mu-Lien

    2013-06-01

    In this work, a method of an inductive coupling impedance measurement (ICIM) is proposed for measuring the nerve impedance of a dorsal root ganglion (DRG) under PRF stimulation. ICIM provides a contactless interface for measuring the reflected impedance by an impedance analyzer with a low excitation voltage of 7 mV. The paper develops a calibration procedure involving a 50-Ω reference resistor to calibrate the reflected resistance for measuring resistance of the nerve in the test. A de-embedding technique to build the equivalent transformer circuit model for the ICIM circuit is also presented. A batteryless PRF stimulator with ICIM circuit demonstrated good accuracy for the acute measurement of DRG impedance both in situ and in vivo. Besides, an in vivo animal experiment was conducted to show that the effectiveness of pulsed radiofrequency (PRF) stimulation in relieving pain gradually declined as the impedance of the stimulated nerve increased. The experiment also revealed that the excitation voltage for measuring impedance below 25 mV can prevent the excitation of a nonlinear response of DRG.

  5. 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

  6. Electrical impedance tomography for assessing ventilation/perfusion mismatch for pulmonary embolism detection without interruptions in respiration.

    PubMed

    Nguyen, Doan Trang; Thiagalingam, Aravinda; Bhaskaran, Abhishek; Barry, Michael A; Pouliopoulos, Jim; Jin, Craig; McEwan, Alistair L

    2014-01-01

    Recent studies have shown high correlation between pulmonary perfusion mapping with impedance contrast enhanced Electrical Impedance Tomography (EIT) and standard perfusion imaging methods such as Computed Tomography (CT) and Single Photon Emission Computerized Tomography (SPECT). EIT has many advantages over standard imaging methods as it is highly portable and non-invasive. Contrast enhanced EIT uses hypertonic saline bolus instead of nephrotoxic contrast medium that are utilized by CT and nuclear Ventilation/Perfusion (V/Q) scans. However, current implementation of contrast enhanced EIT requires induction of an apnea period for perfusion measurement, rendering it disadvantageous compared with current gold standard imaging modalities. In the present paper, we propose the use of a wavelet denoising algorithm to separate perfusion signal from ventilation signal such that no interruption in patient's ventilation would be required. Furthermore, right lung to left lung perfusion ratio and ventilation ratio are proposed to assess the mismatch between ventilation and perfusion for detection of Pulmonary Embolism (PE). The proposed methodology was validated on an ovine model (n=3, 83.7±7.7 kg) with artificially induced PE in the right lung. The results showed a difference in right lung to left lung perfusion ratio between baseline and diseased states in all cases with all paired t-tests between baseline and PE yielding p <; 0.01, while the right lung to left lung ventilation ratio remained unchanged in two out of three experiments. Statistics were pooled from multiple repetitions of measurements per experiment.

  7. Skin-electrode impedance measurement during ECG acquisition: method’s validation

    NASA Astrophysics Data System (ADS)

    Casal, Leonardo; La Mura, Guillermo

    2016-04-01

    Skm-electrode impedance measurement can provide valuable information prior. dunng and post electrocardiographic (ECG) or electroencephalographs (EEG) acquisitions. In this work we validate a method for skm-electrode impedance measurement using test circuits with known resistance and capacitor values, at different frequencies for injected excitation current. Finally the method is successfully used for impedance measurement during ECG acquisition on a subject usmg 125 Hz and 6 nA square wave excitation signal at instrumentation amplifier mput. The method can be used for many electrodes configuration.

  8. Coupling impedance of an in-vacuum undulator: Measurement, simulation, and analytical estimation

    NASA Astrophysics Data System (ADS)

    Smaluk, Victor; Fielder, Richard; Blednykh, Alexei; Rehm, Guenther; Bartolini, Riccardo

    2014-07-01

    One of the important issues of the in-vacuum undulator design is the coupling impedance of the vacuum chamber, which includes tapered transitions with variable gap size. To get complete and reliable information on the impedance, analytical estimate, numerical simulations and beam-based measurements have been performed at Diamond Light Source, a forthcoming upgrade of which includes introducing additional insertion device (ID) straights. The impedance of an already existing ID vessel geometrically similar to the new one has been measured using the orbit bump method. The measurement results in comparison with analytical estimations and numerical simulations are discussed in this paper.

  9. Coupling impedance of an in-vacuum undulator. Measurement, simulation, and analytical estimation

    SciTech Connect

    Simaluk, Victor; Blednykh, Alexei; Fielder, Richard; Rehm, Guenther; Bartolini, Riccardo

    2014-07-25

    One of the important issues of the in-vacuum undulator design is the coupling impedance of the vacuum chamber, which includes tapered transitions with variable gap size. In order to get complete and reliable information on the impedance, analytical estimate, numerical simulations and beam-based measurements have been performed at Diamond Light Source, a forthcoming upgrade of which includes introducing additional insertion device (ID) straights. Moreover, the impedance of an already existing ID vessel geometrically similar to the new one has been measured using the orbit bump method. The measurement results in comparison with analytical estimations and numerical simulations are discussed in this paper.

  10. 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.

  11. Ionosphere plasma electron parameters from radio frequency sweeping impedance probe measurements

    NASA Astrophysics Data System (ADS)

    Spencer, E.; Patra, S.

    2015-09-01

    In this work we will describe the technique of using an RF sweeping impedance probe (SIP) to measure the AC impedance of an electrically short monopole immersed in a plasma. We analyze the SIP measurements which are taken from the payload of the Storms sounding rocket, launched from Wallops Island, Virginia, in 2007. The scientific objective of the Storms mission was to concentrate on whether density irregularities observed in midlatitude spread F could arise from ionospheric coupling to terrestrial weather. As such, independent measurements of the electron density profile are crucial. Since the inherent nature of the SIP technique makes it relatively insensitive to errors introduced through spacecraft charging, probe contamination, and other DC effects, it is an ideal instrument to employ under disturbed plasma conditions. The instrument measures both the magnitude and phase of the AC impedance from 100 kHz to 20 MHz in 128 frequency steps, performing 45,776 sweeps over the entire flight. From these measurements we infer both the absolute electron density ne and the electron neutral collision frequencies νen throughout the flight trajectory. The SIP data can be approximately analyzed using a fluid formulation and thin sheath approximation particularly at altitudes below 200 km, which allows us to match the measurements to quasi-static analytical formulas. At about 265 km on the upleg, the magnitude data transitioned to a highly damped response with increasing altitude. The phase data, on the other hand, continued to indicate increased plasma density and reduced collisionality as expected. For a large portion of the flight, the payload of the Storms mission exhibited an uncontrolled coning motion, making the local magnetic field orientation with respect to the dipole difficult to decipher. Despite these difficulties, we were able to obtain robust estimates of the electron density profile, using the phase information from each sweep. In addition, the electron

  12. Acoustic input impedance of the avian inner ear measured in ostrich (Struthio camelus).

    PubMed

    Muyshondt, Pieter G G; Aerts, Peter; Dirckx, Joris J J

    2016-09-01

    In both mammals and birds, the mechanical behavior of the middle ear structures is affected by the mechanical impedance of the inner ear. In this study, the aim was to quantify the acoustic impedance of the avian inner ear in the ostrich, which allows us to determine the effect on columellar vibrations and middle ear power flow in future studies. To determine the inner ear impedance, vibrations of the columella were measured for both the quasi-static and acoustic stimulus frequencies. In the frequency range of 0.3-4 kHz, we used electromagnetic stimulation of the ossicle and a laser Doppler vibrometer to measure the vibration response. At low frequencies, harmonic displacements were imposed on the columella using piezo stimulation and the resulting force response was measured with a force sensor. From these measurement data, the acoustic impedance of the inner ear could be determined. A simple RLC model in series of the impedance measurements resulted in a stiffness reactance of KIE = 0.20·10(12) Pa/m³, an inertial impedance of MIE = 0.652·10(6) Pa s(2)/m³, and a resistance of RIE = 1.57·10(9) Pa s/m. We found that values of the inner ear impedance in the ostrich are one to two orders in magnitude smaller than what is found in mammal ears.

  13. Electrical Resistivity Measurements: a Review

    NASA Astrophysics Data System (ADS)

    Singh, Yadunath

    World-wide interest on the use of ceramic materials for aerospace and other advanced engineering applications, has led to the need for inspection techniques capable of detecting unusually electrical and thermal anomalies in these compounds. Modern ceramic materials offer many attractive physical, electrical and mechanical properties for a wide and rapidly growing range of industrial applications; moreover specific use may be made of their electrical resistance, chemical resistance, and thermal barrier properties. In this review, we report the development and various techniques for the resistivity measurement of solid kind of samples.

  14. In vivo impedance measurements on nerves and surrounding skeletal muscles in rats and human body.

    PubMed

    Prokhorov, E; Llamas, F; Morales-Sánchez, E; González-Hernández, J; Prokhorov, A

    2002-05-01

    The aim of the work was to use impedance measurements to find the location of nerves under the human skin. In vivo impedance measurements were performed on exposed nervous and muscular tissues of rats. Similarly, the impedance measurements were also performed on the skin of six men, over the median nerve at the wrist, as well as 4-5 mm away from this location. Results obtained with rats have shown that the relative permittivity and conductivity of nerves are larger (by almost two orders of magnitude) than those observed for the muscular tissues surrounding the nerve. The results obtained on human skin in the frequency range of 20-200 kHz, when the electrodes were placed over the nerve, show lower resistance and higher capacitance than in the other areas measured. These preliminary results indicate that it may be possible to use impedance measurements to find the location of exposed nerves and also nerves under the skin.

  15. Real-time gastric motility monitoring using transcutaneous intraluminal impedance measurements (TIIM).

    PubMed

    Poscente, M D; Wang, G; Filip, D; Ninova, P; Yadid-Pecht, O; Andrews, C N; Mintchev, M P

    2014-02-01

    The stomach plays a critical role in digestion, processing ingested food mechanically and breaking it up into particles, which can be effectively and efficiently processed by the intestines. When the motility of the stomach is compromised, digestion is adversely affected. This can lead to a variety of disorders. Current diagnostic techniques for gastric motility disorders are seriously lacking, and are based more on eliminating other possibilities rather than on specific tests. Presently, gastric motility can be assessed by monitoring gastric emptying, food transit, intragastric pressures, etc. The associated tests are usually stationary and of relatively short duration. The present study proposes a new method of measuring gastric motility, utilizing the attenuation of an oscillator-induced electrical signal across the gastric tissue, which is modulated by gastric contractions. The induced high-frequency oscillator signal is generated within the stomach, and is picked up transluminally by cutaneous electrodes positioned on the abdominal area connected to a custom-designed data acquisition instrument. The proposed method was implemented in two different designs: first a transoral catheter was modified to emit the signal inside the stomach; and second, a gastric retentive pill was designed to emit the signal. Both implementations were applied in vivo on two mongrel dogs (25.50 kg and 25.75 kg). Gastric contractions were registered and quantitatively compared to recordings from force transducers sutured onto the serosa of the stomach. Gastric motility indices were calculated for each minute, with transluminal impedance measurements and the measurements from the force transducers showing statistically significant (p < 0.05) Pearson correlation coefficients (0.65 ± 0.08 for the catheter-based design and 0.77 ± 0.03 for the gastric retentive pill design). These results show that transcutaneous intraluminal impedance measurement has the potential with further research

  16. [Measuring the electricity frequency properties of blood].

    PubMed

    Huang, Hua; Hu, Maoqing; Chen, Huaiqing; Yuan, Zirun; Tong, Shan; Luo, An

    2005-04-01

    In order to understand the electricity frequency specialties of blood, we have developed a wide frequency electricity characteristic testing system and used it to test the amplitude frequency property and phase frequency property of the blood in different states and constituents at 1 Hz to 20 MHz. Further analysis on the results of tests helped us know some important properties of blood at even more microcosmic levels from a new angle. Meanwhile, some problems and considerations on the improvement of the electricity model of biotic tissue and blood were pointed out. (1) From 1 Hz to 5 KHz, the impedance of blood descended 99%. (2) Simple equivalent circuit of resistance and capacitance must be used in series equivalent but not in usual parallel connection equivalent. (3) Experiment indicated, equivalent circuits of blood need more analysis, because simple equivalent circuit of resistance and capacitance is liable to gross error. (4) When the three element model is used for measuring the resistance of inside liquid, capacitance of cell membrane and the resistance of outside liquid of blood, the three testing frequencies must be very similar.

  17. Investigation of ground reflection and impedance from flyover noise measurements

    NASA Technical Reports Server (NTRS)

    Chapkis, R. L.; Marsh, A. H.

    1978-01-01

    An extensive series of flyover noise tests was conducted for the primary purpose of studying meteorological effects on propagation of aircraft noise. The test airplane, a DC 9-10, flew several level-flight passes at various heights over a taxiway. Two microphone stations were located under the flight path. A total of 37 runs was selected for analysis and processed to obtain a consistant set of 1/3 octave band sound pressure levels at half-second intervals. The goal of the present study was to use the flyover noise data to deduce acoustical reflection coefficients and hence, acoustical impedances.

  18. High Frequency Electromagnetic Impedance Measurements For Characterization, Monitoring And Verification Efforts

    SciTech Connect

    Lee, Ki Ha; Becker, Alex

    2000-12-31

    Electromagnetic methods in exploration geophysics include many technologies capable of imaging the subsurface. The electromagnetic geophysical spectrum for shallow subsurface imaging is roughly 1 Hz to 500 MHz, with electrical resistivity and other geometric sounding methods located at the low frequency end and the familiar GPR method at the high end of the spectrum. Baseline studies (Pellerin et al., 1997) show that electromagnetic instrumentation in the mid- and low-frequencies (< 300 kHz) and GPR systems (> 30 MHz) are well developed in the commercial sector. In the high-frequency range of 300 kHz to 100 MHz developments have been quite recent and reside within the research community. Accurate theoretical numerical modeling algorithms are available for simulations and interpretation across the entire spectrum (Mackie and Madden, 1993; Pellerin et al., 1995; Pellerin et al., 1997; Alumbaugh and Newman, 1995; Lee et al., 1995, Newmann and Alumbaugh, 1997; Newmann, 1999; Sasaki, 1999, etc.), but instrumentation suitable for collecting calibrated field data in the important high-frequency range is critically lacking. Several attempts to develop reliable, accurate and calibrated instruments (Sternberg and Poulton, 1996; Stewart et al., 1994; Wright et el., 1996) have produced mixed results. We proposed to exploit the concept of electromagnetic impedance, the ratio of orthogonal horizontal electric to horizontal magnetic fields, to provide the necessary technology in the high-frequency band described above. The effective depth of investigation for surface impedance measurements depends on the frequency, and is commonly expressed in terms of the skin depth, the distance into the conductive half space at which the amplitude of the incoming wave has decreased to e-1 of its surface value. In order to achieve skin depths between 0.5 and 10 meters in material of resistivity between 1 and 100 ohm-m and relative permittivity between 1 and 30, frequencies bet ween about 300 k

  19. 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.

  20. 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.

  1. A method for removing artefacts from continuous EEG recordings during functional electrical impedance tomography for the detection of epileptic seizures.

    PubMed

    Fabrizi, L; Yerworth, R; McEwan, A; Gilad, O; Bayford, R; Holder, D S

    2010-08-01

    Electrical impedance tomography (EIT) is a portable, non-invasive medical imaging method, which could be employed to image the seizure onset in subjects undergoing assessment prior to epilepsy surgery. Each image is obtained from impedance measurements conducted with imperceptible current at tens of kHz. For concurrent imaging with video electroencephalogram (EEG), the EIT introduces a substantial artefact into the EEG due to current switching at frequencies in the EEG band. We present here a method for its removal, so that EIT and the EEG could be acquired simultaneously. A low-pass analogue filter for EEG channels (-6 dB at 48 Hz) and a high-pass filter (-3 dB at 72 Hz) for EIT channels reduced the artefact from 2-3 mV to 50-300 microV, but still left a periodic artefact at about 3 Hz. This was reduced to less than 10 microV with a software filter, which subtracted an artefact template from the EEG raw traces. The EEG was made clinically acceptable at four times its acquisition speed. This method could enable EIT to become a technique for imaging on telemetry units alongside EEG, without interfering with routine EEG reporting.

  2. Sensitivity Enhancement of Bead-based Electrochemical Impedance Spectroscopy (BEIS) biosensor by electric field-focusing in microwells.

    PubMed

    Shin, Kyeong-Sik; Ji, Jae Hoon; Hwang, Kyo Seon; Jun, Seong Chan; Kang, Ji Yoon

    2016-11-15

    This paper reports a novel electrochemical impedance spectroscopy (EIS) biosensors that uses magnetic beads trapped in a microwell array to improve the sensitivity of conventional bead-based EIS (BEIS) biosensors. Unloading the previously measured beads by removing the magnetic bar enables the BEIS sensor to be used repeatedly by reloading it with new beads. Despite its recyclability, the sensitivity of conventional BEIS biosensors is so low that it has not attracted much attentions from the biosensor industry. We significantly improved the sensitivity of the BEIS system by introducing of a microwell array that contains two electrodes (a working electrode and a counter electrode) to concentrate the electric field on the surfaces of the beads. We confirmed that the performance of the BEIS sensor in a microwell array using an immunoassay of prostate specific antigen (PSA) in PBS buffer and human plasma. The experimental results showed that a low concentration of PSA (a few tens or hundreds of fg/mL) were detectable as a ratio of the changes in the impedance of the PBS buffer or in human plasma. Therefore, our BEIS sensor with a microwell array could be a promising platform for low cost, high-performance biosensors for applications that require high sensitivity and recyclability.

  3. Measuring Electrolyte Impedance and Noise Simultaneously by Triangular Waveform Voltage and Principal Component Analysis.

    PubMed

    Xu, Shanzhi; Wang, Peng; Dong, Yonggui

    2016-04-22

    In order to measure the impedance variation process in electrolyte solutions, a method of triangular waveform voltage excitation is investigated together with principal component analysis (PCA). Using triangular waveform voltage as the excitation signal, the response current during one duty cycle is sampled to construct a measurement vector. The measurement matrix is then constructed by the measurement vectors obtained from different measurements. After being processed by PCA, the changing information of solution impedance is contained in the loading vectors while the response current and noise information is contained in the score vectors. The measurement results of impedance variation by the proposed signal processing method are independent of the equivalent impedance model. The noise-induced problems encountered during equivalent impedance calculation are therefore avoided, and the real-time variation information of noise in the electrode-electrolyte interface can be extracted at the same time. Planar-interdigitated electrodes are experimentally tested for monitoring the KCl concentration variation process. Experimental results indicate that the measured impedance variation curve reflects the changing process of solution conductivity, and the amplitude distribution of the noise during one duty cycle can be utilized to analyze the contact conditions of the electrode and electrolyte interface.

  4. Measuring Electrolyte Impedance and Noise Simultaneously by Triangular Waveform Voltage and Principal Component Analysis

    PubMed Central

    Xu, Shanzhi; Wang, Peng; Dong, Yonggui

    2016-01-01

    In order to measure the impedance variation process in electrolyte solutions, a method of triangular waveform voltage excitation is investigated together with principal component analysis (PCA). Using triangular waveform voltage as the excitation signal, the response current during one duty cycle is sampled to construct a measurement vector. The measurement matrix is then constructed by the measurement vectors obtained from different measurements. After being processed by PCA, the changing information of solution impedance is contained in the loading vectors while the response current and noise information is contained in the score vectors. The measurement results of impedance variation by the proposed signal processing method are independent of the equivalent impedance model. The noise-induced problems encountered during equivalent impedance calculation are therefore avoided, and the real-time variation information of noise in the electrode-electrolyte interface can be extracted at the same time. Planar-interdigitated electrodes are experimentally tested for monitoring the KCl concentration variation process. Experimental results indicate that the measured impedance variation curve reflects the changing process of solution conductivity, and the amplitude distribution of the noise during one duty cycle can be utilized to analyze the contact conditions of the electrode and electrolyte interface. PMID:27110787

  5. Comparison of segmental with whole-body impedance measurements in peritoneal dialysis patients.

    PubMed

    Nescolarde, Lexa; Doñate, Teresa; Piccoli, Antonio; Rosell, Javier

    2008-09-01

    Segmental impedance measurements were obtained using nine electrode configurations in 21 male patients undergoing peritoneal dialysis PD before and after the fluid drainage. For each segment we analyzed the impedance Z and the impedance divided by the height H of the patient Z/H. Our objective was to compare different segmental measurements with whole-body measurements in peritoneal dialysis. The Wilcoxon test was used to analyze the change in impedance produced by a PD session. Pearson or Spearman correlation coefficients were used for continuous or discrete variables, respectively. Statistical significance was set at P<0.05. Similar results were obtained for Z and Z/H. The correlation coefficients between the real R and imaginary X(c) parts of segmental impedances after drainage were within the expected range for healthy population (0.46-0.70), but not before drainage for the abdomen (0.34) and the upper part of the leg (0.24). The correlation between the real part of whole-body and the real part of longitudinal segments in the limbs was high (r=0.807-0.879). Furthermore, the imaginary part of whole-body showed a high correlation with the imaginary part of all longitudinal segments (r=0.856-0.931). The high contribution of arm and leg impedances in the whole-body impedance produced high correlation between whole-body and segmental measurements in legs and arms. In agreement with other previous studies, a significant increase of the arm resistance was detected after fluid drainage. The drainage of fluids in PD patients produced significant changes in the measured real parts of impedance in all measured segments, but only the measurement in the abdomen showed a significant positive correlation (r=0.533) with the extracted fluid volume. This low correlation indicates that the individual assessment of fluid volumes using segmental measurements will be highly inaccurate.

  6. A partially reflecting random walk on spheres algorithm for electrical impedance tomography

    SciTech Connect

    Maire, Sylvain; Simon, Martin

    2015-12-15

    In this work, we develop a probabilistic estimator for the voltage-to-current map arising in electrical impedance tomography. This novel so-called partially reflecting random walk on spheres estimator enables Monte Carlo methods to compute the voltage-to-current map in an embarrassingly parallel manner, which is an important issue with regard to the corresponding inverse problem. Our method uses the well-known random walk on spheres algorithm inside subdomains where the diffusion coefficient is constant and employs replacement techniques motivated by finite difference discretization to deal with both mixed boundary conditions and interface transmission conditions. We analyze the global bias and the variance of the new estimator both theoretically and experimentally. Subsequently, the variance of the new estimator is considerably reduced via a novel control variate conditional sampling technique which yields a highly efficient hybrid forward solver coupling probabilistic and deterministic algorithms.

  7. State estimation and inverse problems in electrical impedance tomography: observability, convergence and regularization

    NASA Astrophysics Data System (ADS)

    Sbarbaro, D.; Vauhkonen, M.; Johansen, T. A.

    2015-04-01

    Solving electrical impedance tomography (EIT) inverse problems in real-time is a challenging task due to their dimension, the nonlinearities involved and the fact that they are ill-posed. Thus, efficient algorithms are required to address the application of tomographic technologies in process industry. In practical applications the EIT inverse problem is often linearized for fast and robust reconstruction. The aim of this paper is to analyse the solution of linearized EIT inverse problem from the perspective of a state estimation problem, providing links between regularization, observability and convergence of the algorithms. In addition, also a new way to define the fictitious outputs is proposed, leading to observers with fewer parameters than with the approach widely used in literature. Simulation of EIT examples illustrate the main ideas and algorithmic improvements of the proposed approaches.

  8. Sampling of finite elements for sparse recovery in large scale 3D electrical impedance tomography.

    PubMed

    Javaherian, Ashkan; Soleimani, Manuchehr; Moeller, Knut

    2015-01-01

    This study proposes a method to improve performance of sparse recovery inverse solvers in 3D electrical impedance tomography (3D EIT), especially when the volume under study contains small-sized inclusions, e.g. 3D imaging of breast tumours. Initially, a quadratic regularized inverse solver is applied in a fast manner with a stopping threshold much greater than the optimum. Based on assuming a fixed level of sparsity for the conductivity field, finite elements are then sampled via applying a compressive sensing (CS) algorithm to the rough blurred estimation previously made by the quadratic solver. Finally, a sparse inverse solver is applied solely to the sampled finite elements, with the solution to the CS as its initial guess. The results show the great potential of the proposed CS-based sparse recovery in improving accuracy of sparse solution to the large-size 3D EIT.

  9. Design and implementation of a high frequency electrical impedance tomography system.

    PubMed

    Halter, Ryan; Hartov, Alex; Paulsen, Keith D

    2004-02-01

    Electrical impedance tomography is an imaging modality being investigated for use in detection of breast cancer. Use of higher frequencies than have typically been employed may benefit the detection processes. In this current work we discuss the design and initial implementation of a system having a bandwidth of 10 MHz. Previous investigations into high frequency designs have proven more difficult than anticipated and shown that careful selection of systems architecture is critical to achieving broadband performance above 1 MHz. The design for this new system is based on a digital signal processor (DSP) which is used for control, signal generation and signal processing. Signal generation and detection, software design and preliminary system specifications are discussed.

  10. Basic setup for breast conductivity imaging using magnetic resonance electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Lee, Byung Il; Oh, Suk Hoon; Kim, Tae-Seong; Woo, Eung Je; Lee, Soo Yeol; Kwon, Ohin; Seo, Jin Keun

    2006-01-01

    We present a new medical imaging technique for breast imaging, breast MREIT, in which magnetic resonance electrical impedance tomography (MREIT) is utilized to get high-resolution conductivity and current density images of the breast. In this work, we introduce the basic imaging setup of the breast MREIT technique with an investigation of four different imaging configurations of current-injection electrode positions and pathways through computer simulation studies. Utilizing the preliminary findings of a best breast MREIT configuration, additional numerical simulation studies have been carried out to validate breast MREIT at different levels of SNR. Finally, we have performed an experimental validation with a breast phantom on a 3.0 T MREIT system. The presented results strongly suggest that breast MREIT with careful imaging setups could be a potential imaging technique for human breast which may lead to early detection of breast cancer via improved differentiation of cancerous tissues in high-resolution conductivity images.

  11. Electrical Impedance Myography (EIM) in the Evaluation of the Tongue Musculature in Amyotrophic Lateral Sclerosis (ALS)

    PubMed Central

    Shellikeri, Sanjana; Yunusova, Yana; Green, Jordan R.; Pattee, Gary L.; Berry, James D.; Rutkove, Seward B.; Zinman, Lorne

    2015-01-01

    Introduction Electrical impedance myography (EIM) quantifies muscle health and is used as a biomarker of muscle abnormalities in neurogenic and myopathic diseases. EIM has yet to be evaluated in the tongue musculature in people with amyotrophic lateral sclerosis (ALS), who often show clinical bulbar signs. Methods The lingual musculature of 19 subjects with motor neuron disease and 21 of normal participants were assessed using EIM, strength and endurance testing, and clinical observation. Results Tongue musculature in the ALS group was characterized by significantly smaller phase (Ph) and larger resistance (R) when compared to the healthy cohort. Ph and tongue endurance were correlated in the ALS group. Discussion EIM of tongue musculature could distinguish people with ALS from healthy controls. The demonstrated relationship between tongue function and Ph supports further testing of EIM of the tongue as a potential biomarker in ALS. PMID:25580728

  12. Transvers Impedance Measurements of the Modified DARHT-2Accelerator Cell Design

    SciTech Connect

    Briggs, Dick; Waldron, Will

    2005-11-30

    The DARHT-2 accelerator cells have been redesigned to make their high voltage performance more robust. At the outset of the DARHT-2 development program about 8 years ago, an extensive campaign was mounted to minimize the transverse impedance of the original cell design. Since the initial spec on the machine was a beam current of 4 kA, the control of beam-breakup (BBU) amplification with a 2 microsecond pulse length was considered to be one the most critical issues in the design. Even after advances in detector technology allowed the beam current requirement to be lowered to 2 kA, the goal for the standard cell impedance was kept at {approx}300 ohms/meter to allow for the possibility of future beam current upgrades to 4 kA without any modifications in the cells. The results of this campaign to minimize the transverse impedance are described in detail in Reference 1. After several iterations in the design of ferrite dampers and the anode finger stock shape, the measured (peak) impedance of the original standard cell was determined to be about 280 ohms/meter. (As a reference point, the measured impedance of the DARHT-1 cell is about 880 ohms/meter). This impedance provided such a wide safety margin against BBU amplification at 2 kA that it was felt that the cell redesign could focus on voltage holding without any detailed considerations of impacts on the transverse impedance. Now that a baseline design for the DARHT-2 cell has been established and tested, however, it was felt that a measurement of its impedance would be prudent. The results of these impedance measurements are presented in this note. The objective was mainly to do a ''quick check'' to ensure that there were no surprises, and to provide an estimate of the BBU frequencies and growth rates to the experimental test program.

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

    PubMed Central

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

    2016-01-01

    Abstract 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

  14. 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.

  15. Rapid Impedance Spectrum Measurements for Onboard State-of-Health Applications

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chinh D. Ho

    2012-06-01

    Rapid impedance measurements can provide a useful online tool for improved state-of-health estimation. A validation study has been initiated at the Idaho National Laboratory for a rapid impedance technique known as Harmonic Compensated Synchronous Detection. This technique enables capturing the impedance spectra over a broad frequency range within about ten seconds. Commercially available lithium-ion cells are being calendar-life aged at 50°C with reference performance tests at 30°C every 32.5 days to gauge degradation The cells have completed the first set of reference performance tests and preliminary results are presented. The spectra change as a function of temperature and depth-of-discharge condition, as expected. The data indicate that the rapid impedance measurement technique is a benign measurement tool that can be successfully used to gauge changes in the corresponding pulse resistance.

  16. Development of an Arduino-based electrical impedance tomography system with application to dam internal erosion detection

    NASA Astrophysics Data System (ADS)

    Masi, Matteo; Ferdos, Farzad; Losito, Gabriella; Solari, Luca

    2016-04-01

    Electrical Impedance Tomography (EIT) is a technique for the imaging of the electrical properties of conductive materials. In EIT, the spatial distribution of the electrical resistivity or electrical conductivity within a domain is reconstructed using measurements made with electrodes placed at the boundaries of the domain. Data acquisition is typically made by applying an electrical current to the object under investigation using a set of electrodes, and measuring the developed voltage between the other electrodes. The tomographic image is then obtained using an inversion algorithm. This work describes the implementation of a simple and low cost 3D EIT measurement system suitable for laboratory-scale studies. The system was specifically developed for the time-lapse imaging of soil samples subjected to erosion processes during laboratory tests. The tests reproduce the process of internal erosion of soil particles by water flow within a granular media; this process is one of the most common causes of failure of earthen levees and embankment dams. The measurements needed strict requirements of speed and accuracy due to the varying time scale and magnitude of these processes. The developed EIT system consists of a PC which controls I/O cards (multiplexers) through the Arduino micro-controller, an external current generator, a digital acquisition device (DAQ), a power supply and the electrodes. The ease of programming of the Arduino interface greatly helped the implementation of custom acquisition software, increasing the overall flexibility of the system and the creation of specific acquisition schemes and configurations. The system works with a multi-electrode configuration of up to 48 channels but it was designed to be upgraded to an arbitrary large number of electrodes by connecting additional multiplexer cards (> 96 electrodes). The acquisition was optimized for multi-channel measurements so that the overall time of acquisition is dramatically reduced compared to

  17. 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.

  18. Circuits and methods for impedance determination using active measurement cancelation

    DOEpatents

    Jamison, David K.

    2016-12-13

    A delta signal and opposite delta signal are generated such that a sum of the two signals is substantially zero. The delta signal is applied across a first set of electrochemical cells. The opposite delta signal is applied across a second set of electrochemical cells series connected to the first set. A first held voltage is established as the voltage across the first set. A second held voltage is established as the voltage across the second set. A first delta signal is added to the first held voltage and applied to the first set. A second delta signal is added to the second held voltage and applied to the second set. The current responses due to the added delta voltages travel only into the set associated with its delta voltage. The delta voltages and the current responses are used to calculate the impedances of their associated cells.

  19. Sensitive immunodetection through impedance measurements onto gold functionalized electrodes.

    PubMed

    Ameur, S; Martelet, C; Jaffrezic-Renault, N; Chovelon, J M

    2000-01-01

    This article deals with a direct electrochemical method of detecting antigens using new methods of functionalization of gold electrodes. Based on the reacting ability of gold with sulfhydryl groups, three protocols for the fixation of antibodies have been explored. They are based on either the self-assembling properties of functional thiols bearing long alkyl chains or the possibility of a direct coupling of antibody moieties. Coverage rates as high as 97% can be reached. The analysis of the electrochemical impedance behavior of such layers can lead to a sensitive method for the direct detection of the antibody/antigen interaction. The addition of a redox couple in the tested solution, acting as an amplifier, allowed detection limits for the antigens as low as a few picograms/milliliter to be reached.

  20. Light-induced changes in the electrical impedance of the isolated frog retina

    PubMed Central

    Coles, J. A.

    1972-01-01

    1. An isolated frog retina was mounted in an impedance chamber and superfused on its vitread surface. 2. Changes in the real part of the impedance (ΔR) and also in the imaginary part were measured using alternating current in the frequency range 1-300 kHz passed from one surface of the retina to the other. 3. Under most conditions, the response to a flash of light, measured at frequencies below about 100 kHz, was a decrease in the real part of the impedance (ΔR < 0). 4. The geometry of the electrodes was such that the system was particularly sensitive to changes in the impedance of the layer of photo-receptor outer segments. It was confirmed that most of ΔR did arise here and that it was mediated by the absorption of light in rod photo-pigment. 5. The magnitude of ΔR increased when the channels between the outer segments were constricted, e.g. by osmotic swelling of the outer segments. In addition to this increase, a further increase was seen following the commencement of recording in most of the experiments from which usable measurements were obtained. 6. In such retinas, the magnitude of ΔR was greatest when measured at a frequency in the range 3-32 kHz, the largest changes being of the order of 0·1% of the resting value. A light flash bleaching about 1% of the pigment was sufficient to produce this. The onset of ΔR was apparent within 1 msec of the flash (at 15° C); it reached a maximum in 0·5-4 sec and then returned towards the base line. 7. The main component of ΔR was attributed to a decrease in the resistance of the spaces between the outer segments. In addition, there was a resistance increase which occurred at some other site, probably the surface membrane. The first of these components had an onset slightly more rapid than the second, and both occurred irrespective of whether the major cation in the superfusate was sodium or potassium. PMID:4539862

  1. Measurements of Impedance and Attenuation at CENELEC Bands for Power Line Communications Systems

    PubMed Central

    Cavdar, I. Hakki; Karadeniz, Engin

    2008-01-01

    Power line impedance is a very important parameter on the design of power line communications (PLC) modem architecture. Variations on the impedance of the power line affect the communications circuit performance. In order to determine impedance of the power lines, measurements were carried out in Turkey at frequencies ranging from 10 to 170 kHz, (CENELEC A,B,C,D bands). Measurements were conducted in three categories: rural, urban and the industrial power lines. Experimental results are presented in graphical form. The measured impedances were determined as 3-17 ohms, 1-17 ohms, and 1-21 ohms for rural, urban and the industrial lines, respectively. A set of the formulas between impedance and frequency are developed on the power lines using the regression analysis from the obtained empirical data. Signal attenuations on the power lines in the CENELEC band are also measured for rural, urban and industrial regions. Attenuation measurements are repeated for phase-neutral, phase-ground and the neutral-ground conductors. Signal attenuations are found to be 4-30 dB, for different power lines. To establish validity of obtained results for the design of PLC systems, the results are compared with previous investigations. The effects of some household appliances such as TV, PC, UPS, lighting and cooling systems on the impedances and the attenuations for power line communications systems are observed. Some suggestions and proposals are presented for PLC modem designers. PMID:27873974

  2. Influence of measurement procedure on quality of impedance spectra on lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Budde-Meiwes, Heide; Kowal, Julia; Sauer, Dirk Uwe; Karden, Eckhard

    Many battery simulation models, but also electrochemical interpretations are based on impedance spectroscopy. However, the impedance of a battery is influenced by various factors, e.g. in the case of a lead-acid battery: state of charge (SOC), charging or discharging, superimposed dc current, short-term history or homogeneity of the electrolyte. This paper analyses the impact of those factors on impedance spectra of lead-acid batteries. The results show that very detailed information about the conditions during the measurement is crucial for the correct interpretation of a spectrum.

  3. Lord Kelvin's atmospheric electricity measurements

    NASA Astrophysics Data System (ADS)

    Aplin, Karen; Harrison, R. Giles; Trainer, Matthew; Hough, James

    2013-04-01

    Lord Kelvin (William Thomson), one of the greatest Victorian scientists, made a substantial but little-recognised contribution to geophysics through his work on atmospheric electricity. He developed sensitive instrumentation for measuring the atmospheric electric field, including invention of a portable electrometer, which made mobile measurements possible for the first time. Kelvin's measurements of the atmospheric electric field in 1859, made during development of the portable electrometer, can be used to deduce the substantial levels of particulate pollution blown over the Scottish island of Arran from the industrial mainland. Kelvin was also testing the electrometer during the largest solar flare ever recorded, the "Carrington event" in the late summer of 1859. Subsequently, Lord Kelvin also developed a water dropper sensor, and employed photographic techniques for "incessant recording" of the atmospheric electric field, which led to the long series of measurements recorded at UK observatories for the remainder of the 19th and much of the 20th century. These data sets have been valuable in both studies of historical pollution and cosmic ray effects on atmospheric processes.

  4. A new contactless impedance sensor for void fraction measurement of gas-liquid two-phase flow

    NASA Astrophysics Data System (ADS)

    Ji, Haifeng; Chang, Ya; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing

    2016-12-01

    With impedance elimination principle and phase sensitive demodulation (PSD) technique, this work aims to develop a new contactless impedance sensor, which is suitable for the void fraction measurement of gas-liquid two-phase flow. The impedance elimination principle is used to overcome the unfavorable influences of the coupling capacitances, i.e. the capacitive reactances of the coupling capacitances are eliminated by the inductive reactance of an introduced inductor. PSD technique is used to implement the impedance measurement. Unlike the conventional conductance/impedance sensors which use the equivalent conductance (the real part of the impedance) or the amplitude of the impedance of gas-liquid two-phase flow, the new contactless impedance sensor makes full use of the total impedance information of gas-liquid two-phase flow (including the amplitude, the real part and the imaginary part of the impedance, especially the imaginary part) to implement the void fraction measurement. As a preliminary study, to verify the effectiveness of the new contactless impedance sensor, two prototypes (with different inner diameters of 17.0 mm and 22.0 mm) are developed and experiments are carried out. Two typical flow patterns (bubble flow and stratified flow) of gas-liquid two-phase flow are investigated. The experimental results show that the new contactless impedance sensor is successful and effective. Compared with the conventional conductance/impedance sensors, the new contactless impedance sensor can avoid polarization effect and electrochemical erosion effect. The total impedance information is used and the void fraction measurement performance of the new sensor is satisfactory. The experimental results also indicate that the imaginary part of the impedance of gas-liquid two-phase flow is very useful for the void fraction measurement. Making full use of the total impedance information of gas-liquid two-phase flow can effectively improve the void fraction measurement

  5. Experimental investigation of microwave interaction with magnetoplasma in miniature multipolar configuration using impedance measurements

    SciTech Connect

    Dey, Indranuj Toyoda, Yuji; Yamamoto, Naoji; Nakashima, Hideki

    2014-09-15

    A miniature microwave plasma source employing both radial and axial magnetic fields for plasma confinement has been developed for micro-propulsion applications. Plasma is initiated by launching microwaves via a short monopole antenna to circumvent geometrical cutoff limitations. The amplitude and phase of the forward and reflected microwave power is measured to obtain the complex reflection coefficient from which the equivalent impedance of the plasma source is determined. Effect of critical plasma density condition is reflected in the measurements and provides insight into the working of the miniature plasma source. A basic impedance calculation model is developed to help in understanding the experimental observations. From experiment and theory, it is seen that the equivalent impedance magnitude is controlled by the coaxial discharge boundary conditions, and the phase is influenced primarily by the plasma immersed antenna impedance.

  6. Lord Kelvin's atmospheric electricity measurements

    NASA Astrophysics Data System (ADS)

    Aplin, K. L.; Harrison, R. G.

    2013-09-01

    Lord Kelvin (William Thomson) made important contributions to the study of atmospheric electricity during a brief but productive period from 1859-1861. By 1859 Kelvin had recognised the need for "incessant recording" of atmospheric electrical parameters, and responded by inventing both the water dropper equaliser for measuring the atmospheric potential gradient (PG), and photographic data logging. The water dropper equaliser was widely adopted internationally and is still in use today. Following theoretical considerations of electric field distortion by local topography, Kelvin developed a portable electrometer, using it to investigate the PG on the Scottish island of Arran. During these environmental measurements, Kelvin may have unwittingly detected atmospheric PG changes during solar activity in August/September 1859 associated with the "Carrington event", which is interesting in the context of his later statements that solar magnetic influence on the Earth was impossible. Kelvin's atmospheric electricity work presents an early representative study in quantitative environmental physics, through the application of mathematical principles to an environmental problem, the design and construction of bespoke instrumentation for real world measurements and recognising the limitations of the original theoretical view revealed by experimental work.

  7. A motion-compensated cone-beam CT using electrical impedance tomography imaging.

    PubMed

    Pengpan, T; Smith, N D; Qiu, W; Yao, A; Mitchell, C N; Soleimani, M

    2011-01-01

    Cone-beam CT (CBCT) is an imaging technique used in conjunction with radiation therapy. For example CBCT is used to verify the position of lung cancer tumours just prior to radiation treatment. The accuracy of the radiation treatment of thoracic and upper abdominal structures is heavily affected by respiratory movement. Such movement typically blurs the CBCT reconstruction and ideally should be removed. Hence motion-compensated CBCT has recently been researched for correcting image artefacts due to breathing motion. This paper presents a new dual-modality approach where CBCT is aided by using electrical impedance tomography (EIT) for motion compensation. EIT can generate images of contrasts in electrical properties. The main advantage of using EIT is its high temporal resolution. In this paper motion information is extracted from EIT images and incorporated directly in the CBCT reconstruction. In this study synthetic moving data are generated using simulated and experimental phantoms. The paper demonstrates that image blur, created as a result of motion, can be reduced through motion compensation with EIT.

  8. Absolute electrical impedance tomography (aEIT) guided ventilation therapy in critical care patients: simulations and future trends.

    PubMed

    Denaï, Mouloud A; Mahfouf, Mahdi; Mohamad-Samuri, Suzani; Panoutsos, George; Brown, Brian H; Mills, Gary H

    2010-05-01

    Thoracic electrical impedance tomography (EIT) is a noninvasive, radiation-free monitoring technique whose aim is to reconstruct a cross-sectional image of the internal spatial distribution of conductivity from electrical measurements made by injecting small alternating currents via an electrode array placed on the surface of the thorax. The purpose of this paper is to discuss the fundamentals of EIT and demonstrate the principles of mechanical ventilation, lung recruitment, and EIT imaging on a comprehensive physiological model, which combines a model of respiratory mechanics, a model of the human lung absolute resistivity as a function of air content, and a 2-D finite-element mesh of the thorax to simulate EIT image reconstruction during mechanical ventilation. The overall model gives a good understanding of respiratory physiology and EIT monitoring techniques in mechanically ventilated patients. The model proposed here was able to reproduce consistent images of ventilation distribution in simulated acutely injured and collapsed lung conditions. A new advisory system architecture integrating a previously developed data-driven physiological model for continuous and noninvasive predictions of blood gas parameters with the regional lung function data/information generated from absolute EIT (aEIT) is proposed for monitoring and ventilator therapy management of critical care patients.

  9. Non-invasive measurement of micro-area skin impedance in vivo

    NASA Astrophysics Data System (ADS)

    Li, Dachao; Liang, Wenshuai; Liu, Tongkun; Yu, Haixia; Xu, Kexin

    2011-12-01

    Volume measurement of interstitial fluid transdermally extracted is important in continuous glucose monitoring instrument. The volume of transdermally extracted interstitial fluid could be determined by a skin permeability coefficient. If the skin impedance which is the indicator of skin permeability coefficient can be accurately measured, the volume of interstitial fluid can be calculated based on the relationship between the indicator and the skin permeability coefficient. The possibility of using the skin impedance to indicate the skin permeability coefficient is investigated. A correlation model between the skin impedance and the skin permeability coefficient is developed. A novel non-invasive method for in vivo, real-time, and accurate measurement of skin impedance within a micro skin area is brought forward. The proposed measurement method is based on the theory that organisms saliva and interstitial fluid are equipotential. An electrode is put on the surface of a micro skin area and another one is put in the mouth to be fully contacted with saliva of an animal in the experiments. The electrode in mouth is used to replace the implantable subcutaneous electrode for non-invasive measurement of skin impedance in vivo. A biologically compatible AC current with amplitude of 100mv and frequency of 10Hz is applied to stimulate the micro skin area by the two electrodes. And then the voltage and current between the two electrodes are measured to calculate the skin impedance within a micro skin area. The measurement results by electrode in mouth are compared with the results by subcutaneous electrode in animal experiments and they are consistent so the proposed measurement method is verified well. The effect of moisture and pressure for the measurement is also studied in the paper.

  10. Temperature-stable parallel-plate dielectric cell for broadband liquid impedance measurements

    NASA Astrophysics Data System (ADS)

    Mazzeo, Brian A.; Chandra, Satyan; Mellor, Brett L.; Arellano, Jesus

    2010-12-01

    A liquid impedance cell for broadband impedance measurements up to 110 MHz is presented. The design incorporates temperature control and minimizes parasitic capacitance and inductance. The cell is simple to fabricate and uses chemically resistant materials, stainless steel, and Teflon. This dielectric cell can be used in a variety of liquid measurements, particularly those related to impedance measurements of biological objects in solution. Temperature control is illustrated in measurements of the permittivity of deionized water from 5 to 55 °C. Numerical fitting procedures employed on the relaxation curves indicate good agreement with previous studies on beta-lactoglobulin and hen lysozyme. Titration capability is demonstrated through dielectric titration of hen lysozyme and beta-lactoglobulin.

  11. Particle trapping and impedance measurement using bilayer electrodes integrated with microcavity structure

    NASA Astrophysics Data System (ADS)

    Chen, Guan-Ting; Liu, Chia-Feng; Jang, Ling-Sheng; Li, Shun-Lai; Wang, Min-Haw

    2017-03-01

    Traditional planar electrodes for single-particle impedance measurement have difficulty in trapping and positioning particles. This paper proposes a microfluidic device for single-particle trapping and impedance measurement with a microcavity configuration. A carbon dioxide (CO2) laser technique was used to fabricate the microcavity structure, which can capture 15 µm diameter particles without requiring additional trapping structures. The measurement electrodes on both sides of the microcavity were fabricated using electroplating and deposition techniques. The advantages of the microcavity structure and electrodes are discussed. The bottom electrode spreads into the microcavity to increase measurement sensitivity and shrink the exit aperture to around 10 µm for particle trapping. The experimental results show that the device successfully captured particles and distinguished the impedance of a particle from that of phosphate-buffered saline solution.

  12. Development of a portable electrical impedance tomography data acquisition system for near-real-time spatial sensing

    NASA Astrophysics Data System (ADS)

    Huang, Shieh-Kung; Loh, Kenneth J.

    2015-04-01

    The main goal of this study was to develop and validate the performance of a miniature and portable data acquisition (DAQ) system designed for interrogating carbon nanotube (CNT)-based thin films for real-time spatial structural sensing and damage detection. Previous research demonstrated that the electrical properties of CNT-based thin film strain sensors were linearly correlated with applied strains. When coupled with an electrical impedance tomography (EIT) algorithm, the detection and localization of damage was possible. In short, EIT required that the film or "sensing skin" be interrogated along its boundaries. Electrical current was injected across a pair of boundary electrodes, and voltage was simultaneously recorded along the remaining electrode pairs. This was performed multiple times to obtain a large dataset needed for solving the EIT spatial conductivity mapping inverse problem. However, one of the main limitations of this technique was the large amount of time required for data acquisition. In order to facilitate the adoption of this technology and for field implementation purposes, a miniature DAQ that could interrogate these CNT-based sensing skins at high sampling rates was designed and tested. The prototype DAQ featured a Howland current source that could generate stable and controlled direct current. Measurement of boundary electrode voltages and the switching of the input, output, and measurement channels were achieved using multiplexer units. The DAQ prototype was fabricated on a two-layer printed circuit board, and it was designed for integration with a prototype wireless sensing system, which is the next phase of this research.

  13. Different approaches to the completion of the back-projection algorithm in image monitoring by electrical impedance tomography.

    PubMed

    Wanjun, Shuai; Xiuzhen, Dong; Feng, Fu; Fusheng, You; Xiaodong, Liu; Canhua, Xu

    2005-01-01

    It is found that Electrical Impedance Tomography(EIT) is promising in its application to the clinical image monitoring and that the Back-Projection algorithm of EIT can meet the preliminary requirements of the real-time monitoring through our work. In order to improve the computed speed and the imaged resolution, different ways of completing the algorithm were tried in this paper. Moreover, it is shown that the impedance change due to physiological saline with the concentration of not more than 50 milliliter 0.9% can be detected and imaged by our system. The above result is helpful for our further work of image monitoring by EIT.

  14. Non-invasive measurement of cholesterol in human blood by impedance technique: an investigation by 3D finite element field modelling

    NASA Astrophysics Data System (ADS)

    Aristovich, Ekaterina; Khan, Sanowar

    2013-06-01

    This paper concerns detection of particle concentration (e.g. cholesterol) in conductive media (e.g. human blood) by impedance technique. The technique is based on changes in the impedance measurement across a given conducting medium due to changes in the particle concentration. The impedance is calculated by calculating the current through the conducting media produced by electric field distribution between two electrodes. This is done by modelling and computation of 3D electric fields between the electrodes for known voltages applied between them using the well-known finite element method (FEM). The complexity of such FE models is attributed to particle distribution, their geometric and material parameters, and their shape and size which can be of many orders of magnitude smaller than the overall problem domain under investigation. This paper overcomes this problem by adopting an effective particle coagulation (aggregation) strategy in FE modelling without significantly affecting the accuracy of field computation.

  15. Electrical/electrochemical impedance for rapid detection of foodborne pathogenic bacteria.

    PubMed

    Yang, Liju; Bashir, Rashid

    2008-01-01

    The realization of rapid, sensitive, and specific methods to detect foodborne pathogenic bacteria is central to implementing effective practice to ensure food safety and security. As a principle of transduction, the impedance technique has been applied in the field of microbiology as a means to detect and/or quantify foodborne pathogenic bacteria. The integration of impedance with biological recognition technology for detection of bacteria has led to the development of impedance biosensors that are finding wide-spread use in the recent years. This paper reviews the progress and applications of impedance microbiology for foodborne pathogenic bacteria detection, particularly the new aspects that have been added to this subject in the past few years, including the use of interdigitated microelectrodes, the development of chip-based impedance microbiology, and the use of equivalent circuits for analysis of the impedance systems. This paper also reviews the significant developments of impedance biosensors for bacteria detection in the past 5 years, focusing on microfabricated microelectrodes-based and microfluidic-based Faradaic electrochemical impedance biosensors, non-Faradaic impedance biosensors, and the integration of impedance biosensors with other techniques such as dielectrophoresis and electropermeabilization.

  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. Non-invasive evaluation of muscle disease in the canine model of Duchenne muscular dystrophy by electrical impedance myography

    PubMed Central

    Hakim, Chady H.; Mijailovic, Alex; Lessa, Thais B.; Coates, Joan R.; Shin, Carmen; Rutkove, Seward B.; Duan, Dongsheng

    2017-01-01

    Dystrophin-deficient dogs are by far the best available large animal models for Duchenne muscular dystrophy (DMD), the most common lethal childhood muscle degenerative disease. The use of the canine DMD model in basic disease mechanism research and translational studies will be greatly enhanced with the development of reliable outcome measures. Electrical impedance myography (EIM) is a non-invasive painless procedure that provides quantitative data relating to muscle composition and histology. EIM has been extensively used in neuromuscular disease research in both human patients and rodent models. Recent studies suggest that EIM may represent a highly reliable and convenient outcome measure in DMD patients and the mdx mouse model of DMD. To determine whether EIM can be used as a biomarker of disease severity in the canine model, we performed the assay in fourteen young (~6.6-m-old; 6 normal and 8 affected) and ten mature (~16.9-m-old; 4 normal and 6 affected) dogs of mixed background breeds. EIM was well tolerated with good inter-rater reliability. Affected dogs showed higher resistance, lower reactance and phase. The difference became more straightforward in mature dogs. Importantly, we observed a statistically significant correlation between the EIM data and muscle fibrosis. Our results suggest that EIM is a valuable objective measurement in the canine DMD model. PMID:28339469

  18. Non-invasive evaluation of muscle disease in the canine model of Duchenne muscular dystrophy by electrical impedance myography.

    PubMed

    Hakim, Chady H; Mijailovic, Alex; Lessa, Thais B; Coates, Joan R; Shin, Carmen; Rutkove, Seward B; Duan, Dongsheng

    2017-01-01

    Dystrophin-deficient dogs are by far the best available large animal models for Duchenne muscular dystrophy (DMD), the most common lethal childhood muscle degenerative disease. The use of the canine DMD model in basic disease mechanism research and translational studies will be greatly enhanced with the development of reliable outcome measures. Electrical impedance myography (EIM) is a non-invasive painless procedure that provides quantitative data relating to muscle composition and histology. EIM has been extensively used in neuromuscular disease research in both human patients and rodent models. Recent studies suggest that EIM may represent a highly reliable and convenient outcome measure in DMD patients and the mdx mouse model of DMD. To determine whether EIM can be used as a biomarker of disease severity in the canine model, we performed the assay in fourteen young (~6.6-m-old; 6 normal and 8 affected) and ten mature (~16.9-m-old; 4 normal and 6 affected) dogs of mixed background breeds. EIM was well tolerated with good inter-rater reliability. Affected dogs showed higher resistance, lower reactance and phase. The difference became more straightforward in mature dogs. Importantly, we observed a statistically significant correlation between the EIM data and muscle fibrosis. Our results suggest that EIM is a valuable objective measurement in the canine DMD model.

  19. The Mutual Impedance Probe Technique for Plasma Parameters Measurements: the ROSETTA RPC/MIP Results during the Earth's Flybys

    NASA Astrophysics Data System (ADS)

    Trotignon, J.; Lebreton, J.; Rauch, J.

    2010-12-01

    The Mutual Impedance Probe technique, used in geophysical prospection to measure the ground permittivity since the early 1900, has been successfully transposed to measure space plasma properties in the 70s. This technique has been used in space for many years on sounding rockets and spacecraft: GEOS-1, GEOS-2, VIKING, MARS-96, ARCAD/AUREOL-3, and Huygens. The basic principle of the technique is to measure the self impedance of a single electric antenna or the mutual impedance between two sets of E-field dipoles. Since the impedance of the probe depends on the dielectric properties of the medium in which the probe is immersed, some characteristics of the medium can be determined. Space plasma parameters such as the density and temperature of thermal electrons may thus be reliably and accurately deduced. As a bonus, using only the receiving part of the probe, natural waves can also be investigated in a large frequency range. An E-field impedance probe is currently flying onboard ESA’s comet Chaser ROSETTA and one such probe is in development for BepiColombo. The most common configuration of a mutual impedance probe uses a dipole for transmitting a frequency-controlled signal and a second dipole for receiving the induced signal. Transmitting electrodes are fed with a signal generator, in series with a current meter if necessary, while the receiving electrodes are connected to a voltmeter with a very high input impedance. The transmitted current I and the received voltage V being known, the mutual impedance Z is by definition Z = V/I. Both the imaginary and the real parts of Z may then be interpreted to deduce plasma properties. The capabilities of this technique are illustrated with in-flight calibration results obtained by the Mutual Impedance Probe, MIP, which is one instrument of the ROSETTA plasma package. MIP and the four other instruments of the ROSETTA Plasma Consortium, RPC, were switched on during the three Earth swingbys (March 2005, November 2007, and

  20. Crew Quarters (CQ) and Electromagnetic Interference (EMI) Measurement Facility Combined Impedance Study

    NASA Technical Reports Server (NTRS)

    Scully, Robert C.

    2011-01-01

    This report documents an investigation into observed failures associated with conducted susceptibility testing of Crew Quarters (CQ) hardware in the Johnson Space Center (JSC) Electromagnetic Interference (EMI) Measurement Facility, and the work accomplished to identify the source of the observed behavior. Investigation led to the conclusion that the hardware power input impedance was interacting with the facility power impedance leading to instability at the observed frequencies of susceptibility. Testing performed in other facilities did not show this same behavior, pointing back to the EMI Measurement Facility power as the potential root cause. A LISN emulating the Station power bus impedance was inserted into the power circuit, and the susceptibility was eliminated from the measurements.

  1. A frequency-response-based method of sound velocity measurement in an impedance tube

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Thomas, P. J.; Wang, Tongqing

    2017-04-01

    A stable and accurate new method for the measurement of the velocity of sound is proposed. The method is based on the characteristics of the frequency response measured at different positions in an impedance tube and it eliminates adverse effects caused by reflections from the transmitting transducer at the bottom of the impedance tube. A series of experiments is conducted, at different water temperatures, different positions in the impedance tube and under constant pressure, to validate the feasibility and stability of the new method. The new technique is also extended to hydrostatic pressure conditions with stable sound velocity. Our method generates an accurate measurement result in comparison to the estimated or average value obtained with currently existing methods. The novel method is suitable to be widely used in underwater acoustics.

  2. A Deformable Smart Skin for Continuous Sensing Based on Electrical Impedance Tomography

    PubMed Central

    Visentin, Francesco; Fiorini, Paolo; Suzuki, Kenji

    2016-01-01

    In this paper, we present a low-cost, adaptable, and flexible pressure sensor that can be applied as a smart skin over both stiff and deformable media. The sensor can be easily adapted for use in applications related to the fields of robotics, rehabilitation, or costumer electronic devices. In order to remove most of the stiff components that block the flexibility of the sensor, we based the sensing capability on the use of a tomographic technique known as Electrical Impedance Tomography. The technique allows the internal structure of the domain under study to be inferred by reconstructing its conductivity map. By applying the technique to a material that changes its resistivity according to applied forces, it is possible to identify these changes and then localise the area where the force was applied. We tested the system when applied to flat and curved surfaces. For all configurations, we evaluate the artificial skin capabilities to detect forces applied over a single point, over multiple points, and changes in the underlying geometry. The results are all promising, and open the way for the application of such sensors in different robotic contexts where deformability is the key point. PMID:27854325

  3. An implantable left ventricular assist system with an electrical impedance monitoring and control system.

    PubMed

    Nakatani, T; Anai, H; Taenaka, Y; Akagi, H; Masuzawa, T; Baba, Y; Sakaki, M; Araki, K; Inoue, K; Matsuo, Y

    1993-01-01

    The authors developed an implantable left ventricular assist system (LVAS) for bridge to transplant of rather small sized adults. The pump was made of segmented polyether polyurethane and was 86 mm in diameter, 50 mm in height, with a 70 ml nominal stroke volume. A percutaneous drive line was connected with an external pneumatic control drive unit (CDU). In chronic animal experiments using 11 adult goats, the pump was installed between the LV apex and the descending aorta and was placed in the abdominal wall. Five goats were killed after 4 to 14 weeks while in good physical condition, and one is ongoing. There were no prominent thromboembolic symptoms despite no anti-thrombogenic agent being used. The new electrical impedance-based monitoring and control system (Z system) was installed in the CDU. In this Z system, automatic calibration was performed periodically for several seconds while the drive condition was changed to ensure full-fill of the blood pump. The full-fill to full-empty drive was well controlled by this Z system. In conclusion, the new Z system is practical and useful for monitoring and control of an implantable pump, giving this LVAS a promising place in clinical use.

  4. Electrical Impedance Monitoring of C2C12 Myoblast Differentiation on an Indium Tin Oxide Electrode

    PubMed Central

    Park, Ilhwan; Hong, Yeonhee; Jun, Young-Hoo; Lee, Ga-Yeon; Jun, Hee-Sook; Pyun, Jae-Chul; Choi, Jeong-Woo; Cho, Sungbo

    2016-01-01

    Electrical cell-substrate impedance sensing is increasingly being used for label-free and real-time monitoring of changes in cell morphology and number during cell growth, drug screening, and differentiation. In this study, we evaluated the feasibility of using ECIS to monitor C2C12 myoblast differentiation using a fabricated indium tin oxide (ITO) electrode-based chip. C2C12 myoblast differentiation on the ITO electrode was validated based on decreases in the mRNA level of MyoD and increases in the mRNA levels of myogenin and myosin heavy chain (MHC). Additionally, MHC expression and morphological changes in myoblasts differentiated on the ITO electrode were comparable to those in cells in the control culture dish. From the monitoring the integration of the resistance change at 21.5 kHz, the cell differentiation was label-free and real-time detectable in 30 h of differentiation (p < 0.05). PMID:27929401

  5. 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.

  6. 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.

  7. 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.

  8. A Basic Study About Multi Channel Measurement of Skin Impedance Vector Loci on the Acupuncture Points

    DTIC Science & Technology

    2007-11-02

    Agency Name(s) and Address(es) US Army Research, Development & Standardization Group (UK) PSC 802 Box 15 FPO AE 09499-1500 Sponsor/Monitor’s Acronym(s...each measurement we perform. Additionally, we applied the results obtained to per- foming 4 channel measurments of skin impedance vector loci around

  9. Rapid Impedance Spectrum Measurements for State-of-Health Assessment of Energy Storage Devices

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chester G. Motloch; William H. Morrison

    2012-04-01

    Harmonic compensated synchronous detection (HCSD) is a technique that can be used to measure wideband impedance spectra within seconds based on an input sum-of-sines signal having a frequency spread separated by harmonics. The battery (or other energy storage device) is excited with a sum-of-sines current signal that has a duration of at least one period of the lowest frequency. The voltage response is then captured and synchronously detected at each frequency of interest to determine the impedance spectra. This technique was successfully simulated using a simplified battery model and then verified with commercially available Sanyo lithium-ion cells. Simulations revealed the presence of a start-up transient effect when only one period of the lowest frequency is included in the excitation signal. This transient effect appears to only influence the low-frequency impedance measurements and can be reduced when a longer input signal is used. Furthermore, lithium-ion cell testing has indicated that the transient effect does not seem to impact the charge transfer resistance in the mid-frequency region. The degradation rates for the charge transfer resistance measured from the HCSD technique were very similar to the changes observed from standardized impedance spectroscopy methods. Results from these studies, therefore, indicate that HCSD is a viable, rapid alternative approach to acquiring impedance spectra.

  10. Studies of longitudinal profile of electron bunches and impedance measurements at Indus-2 synchrotron radiation source

    NASA Astrophysics Data System (ADS)

    Garg, Akash Deep; Yadav, S.; Kumar, Mukesh; Shrivastava, B. B.; Karnewar, A. K.; Ojha, A.; Puntambekar, T. A.

    2016-04-01

    Indus-2 is a 3rd generation synchrotron radiation source at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We study the longitudinal profile of electrons in Indus-2 by using dual sweep synchroscan streak camera at visible diagnostic beamline. In this paper, the longitudinal profiles of electron bunch are analyzed by filling beam current in a single bunch mode. These studies are carried at injection energy (550 MeV) and at ramped beam energy (2.5 GeV). The effects of the wakefield generated interactions between the circulating electrons and the surrounding vacuum chamber are analyzed in terms of measured effects on longitudinal beam distribution. The impedance of the storage ring is obtained by fitting the solutions of Haissinski equation to the measured bunch lengthening with different impedance models. The impedance of storage ring obtained by a series R+L impedance model indicates a resistance (R) of 1350±125 Ω, an inductance (L) of 180±25 nH and broadband impedance of 2.69 Ω. These results are also compared with the values obtained from measured synchronous phase advancing and scaling laws. These studies are very useful in better understanding and control of the electromagnetic interactions.

  11. LDV measurement of bird ear vibrations to determine inner ear impedance and middle ear power flow

    NASA Astrophysics Data System (ADS)

    Muyshondt, Pieter G. G.; Pires, Felipe; Dirckx, Joris J. J.

    2016-06-01

    The mechanical behavior of the middle ear structures in birds and mammals is affected by the fluids in the inner ear (IE) that are present behind the oval window. In this study, the aim was to gather knowledge of the acoustic impedance of the IE in the ostrich, to be able to determine the effect on vibrations and power flow in the single-ossicle bird middle ear for future studies. To determine the IE impedance, vibrations of the ossicle were measured for both the quasi-static and acoustic stimulus frequencies. In the acoustic regime, vibrations were measured with a laser Doppler vibrometer and electromagnetic stimulation of the ossicle. The impedance of the inner ear could be determined by means of a simple RLC model in series, which resulted in a stiffness reactance of KIE = 0.20.1012 Pa/m3, an inertial impedance of MIE = 0.652.106 Pa s2/m3, and a resistance of RIE = 1.57.109 Pa s/m. The measured impedance is found to be considerably smaller than what is found for the human IE.

  12. In vivo measurement of mechanical impedance of bone

    NASA Technical Reports Server (NTRS)

    Young, D. R.; Thompson, G.

    1974-01-01

    System of measurement provides indications of ulnar properties independent of characteristics of surrounding soft tissue and other bones. Mechanical modal approximated ulnar response so average bending rigidity could be determined to provide direct index of bone resistance to bending loading.

  13. UNIVERSAL AUTO-CALIBRATION FOR A RAPID BATTERY IMPEDANCE SPECTRUM MEASUREMENT DEVICE

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; William H. Morrison

    2014-03-01

    Electrochemical impedance spectroscopy has been shown to be a valuable tool for diagnostics and prognostics of energy storage devices such as batteries and ultra-capacitors. Although measurements have been typically confined to laboratory environments, rapid impedance spectrum measurement techniques have been developed for on-line, embedded applications as well. The prototype hardware for the rapid technique has been validated using lithium-ion batteries, but issues with calibration had also been identified. A new, universal automatic calibration technique was developed to address the identified issues while also enabling a more simplified approach. A single, broad-frequency range is used to calibrate the system and then scaled to the actual range and conditions used when measuring a device under test. The range used for calibration must be broad relative to the expected measurement conditions for the scaling to be successful. Validation studies were performed by comparing the universal calibration approach with data acquired from targeted calibration ranges based on the expected range of performance for the device under test. First, a mid-level shunt range was used for calibration and used to measure devices with lower and higher impedance. Next, a high excitation current level was used for calibration, followed by measurements using lower currents. Finally, calibration was performed over a wide frequency range and used to measure test articles with a lower set of frequencies. In all cases, the universal calibration approach compared very well with results acquired following a targeted calibration. Additionally, the shunts used for the automated calibration technique were successfully characterized such that the rapid impedance measurements compare very well with laboratory-scale measurements. These data indicate that the universal approach can be successfully used for onboard rapid impedance spectra measurements for a broad set of test devices and range of

  14. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion.

    PubMed

    Bartholomew, Paul D; Guthrie, W Spencer; Mazzeo, Brian A

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  15. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion

    NASA Astrophysics Data System (ADS)

    Bartholomew, Paul D.; Guthrie, W. Spencer; Mazzeo, Brian A.

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  16. Measuring the Six dof Driving Point Impedance Function and AN Application to RB Inertia Property Estimation

    NASA Astrophysics Data System (ADS)

    Witter, M. C.; Brown, D. L.; Blough, J. R.

    2000-01-01

    An accurate driving point measurement is imperative in structural dynamic testing. For example, it is used to derive modal scaling, for experimental correlation of finite element models, impedance modelling and extracting the rigid body (RB) inertia properties of an object. A typical driving point measurement gives the linear force/displacement relationship at a single degree of freedom (dof), but any point on an object actually has rotational dofs as well. For example these rotational dofs must be measured in an impedance model where moments are transmitted at the connection point of two substructures. By ignoring the rotations, an inaccurate model will result. In the past, dynamic sensing technology has been limited to the accurate measurement of translational dofs. While rotational sensors do exist, their accuracy is called into question for certain applications. Rotational dofs have tended to be ignored in the measurement process. Applications, which require their use, such as impedance modelling and RB inertia property estimation, have suffered as a result. A process/sensor is being developed to accurately measure the driving point impedance function in all six dofs. The sensor as well as a calibration procedure will be presented here. In order to verify the validity of the calibration and measurement procedure, a new method for measuring the RB inertia properties of an object will be presented. This new method requires an accurate six dof driving point impedance measurement to provide accurate results. The inertia properties of an automotive brake rotor will be measured and compared with the results of a traditional pendulous swing test.

  17. Longitudinal impedance measurement of an RK-TBA induction accelerating gap

    SciTech Connect

    Eylon, S.; Henestroza, E.; Kim, J.-S.; Houck, T.L.; Westenskow, G.A.; Yu, S.S.

    1997-05-01

    Induction accelerating gap designs are being studied for Relativistic Klystron Two-Beam Accelerator (RK-TBA) applications. The accelerating gap has to satisfy the following major requirements: hold-off of the applied accelerating voltage pulse, low transverse impedance to limit beam breakup, low longitudinal impedance at the beam-modulation frequency to minimize power loss. Various gap geometries, materials and novel insulating techniques were explored to optimize the gap design. We report on the experimental effort to evaluate the rf properties of the accelerating gaps in a simple pillbox cavity structure. The experimental cavity setup was designed using the AMOS, MAFIA and URMEL numerical codes. Longitudinal impedance measurements above beam-tube cut-off frequency using a single-wire measuring system are presented.

  18. An Electronic Measurement Instrumentation of the Impedance of a Loaded Fuel Cell or Battery

    PubMed Central

    Aglzim, El-Hassane; Rouane, Amar; El-Moznine, Reddad

    2007-01-01

    In this paper we present an inexpensive electronic measurement instrumentation developed in our laboratory, to measure and plot the impedance of a loaded fuel cell or battery. Impedance measurements were taken by using the load modulation method. This instrumentation has been developed around a VXI system stand which controls electronic cards. Software under Hpvee® was developed for automatic measurements and the layout of the impedance of the fuel cell on load. The measurement environment, like the ambient temperature, the fuel cell temperature, the level of the hydrogen, etc…, were taken with several sensors that enable us to control the measurement. To filter the noise and the influence of the 50Hz, we have implemented a synchronous detection which filters in a very narrow way around the useful signal. The theoretical result obtained by a simulation under Pspice® of the method used consolidates the choice of this method and the possibility of obtaining correct and exploitable results. The experimental results are preliminary results on a 12V vehicle battery, having an inrush current of 330A and a capacity of 40Ah (impedance measurements on a fuel cell are in progress, and will be the subject of a forthcoming paper). The results were plotted at various nominal voltages of the battery (12.7V, 10V, 8V and 5V) and with two imposed currents (0.6A and 4A). The Nyquist diagram resulting from the experimental data enable us to show an influence of the load of the battery on its internal impedance. The similitude in the graph form and in order of magnitude of the values obtained (both theoretical and practical) enables us to validate our electronic measurement instrumentation. One of the future uses for this instrumentation is to integrate it with several control sensors, on a vehicle as an embedded system to monitor the degradation of fuel cell membranes.

  19. Facts and artefacts regarding correlation between skin electrical impedance spectroscopy (EIS) and blood glucose

    NASA Astrophysics Data System (ADS)

    Ollmar, Stig; Nicander, Ingrid; Åberg, Peter; Bolinder, Jan

    2013-04-01

    Earlier observations on possible co-variation between skin EIS and blood glucose prompted us to map and include other factors at play in the predictive model. Skin pH would be one such factor. A cohort of 20 diabetics was investigated, taking around 30 measurements spread over each of two different days 2-21 days apart. Each measurement comprises skin EIT in the frequency range 1kHz to 2.5MHz, skin pH, and immediately evaluated blood samples. There is a co-variation for some, but not all, test persons. The relationship gets stronger on the group level by adding pH-information, but is still poor or non-existent for some test persons. Non-invasive EIS measurements on skin is influenced by skin hydration, blood glucose, skin pH, body location, season, environmental factors, and variables not yet understood. Since impedance related parameters are used to estimate skin hydration, users of such devices should be aware that skin pH may influence as much as the water content of the stratum corneum.

  20. The use of electro-acoustic impedance measurements in detecting early clinical otosclerosis.

    PubMed

    Van Wagoner, R S; Campbell, J D

    1976-02-01

    The first evidence that sodium fluoride (NaFl) can stop the otosclerotic process was recently presented. This development has placed new emphasis on the early detection of clinical otosclerosis. Electro-acoustic impedance measurements often detect minute changes in absolute impedance and compliance of the ossicular chain. The most valuable diagnostic information, however, is a negative on-off (biphasic) type of acoustic reflex. These results are often evident prior to the detection of positive clinical signs of otosclerosis. The negative on-off acoustic reflex is reviewed in this paper along with case discussions involving medical/surgical management of early otosclerosis.

  1. Automatic protective ventilation using the ARDSNet protocol with the additional monitoring of electrical impedance tomography

    PubMed Central

    2014-01-01

    Introduction Automatic ventilation for patients with respiratory failure aims at reducing mortality and can minimize the workload of clinical staff, offer standardized continuous care, and ultimately save the overall cost of therapy. We therefore developed a prototype for closed-loop ventilation using acute respiratory distress syndrome network (ARDSNet) protocol, called autoARDSNet. Methods A protocol-driven ventilation using goal-oriented structural programming was implemented and used for 4 hours in seven pigs with lavage-induced acute respiratory distress syndrome (ARDS). Oxygenation, plateau pressure and pH goals were controlled during the automatic ventilation therapy using autoARDSNet. Monitoring included standard respiratory, arterial blood gas analysis and electrical impedance tomography (EIT) images. After 2-hour automatic ventilation, a disconnection of the animal from the ventilator was carried out for 10 seconds, simulating a frequent clinical scenario for routine clinical care or intra-hospital transport. Results This pilot study of seven pigs showed stable and robust response for oxygenation, plateau pressure and pH value using the automated system. A 10-second disconnection at the patient-ventilator interface caused impaired oxygenation and severe acidosis. However, the automated protocol-driven ventilation was able to solve these problems. Additionally, regional ventilation was monitored by EIT for the evaluation of ventilation in real-time at bedside with one prominent case of pneumothorax. Conclusions We implemented an automatic ventilation therapy using ARDSNet protocol with seven pigs. All positive outcomes were obtained by the closed-loop ventilation therapy, which can offer a continuous standard protocol-driven algorithm to ARDS subjects. PMID:24957974

  2. Real-Time Electrical Impedance Variations in Women With and Without Breast Cancer

    PubMed Central

    Hartov, Alex; Poplack, Steven P.; diFlorio-Alexander, Roberta; Wells, Wendy A.; Rosenkranz, Kari M.; Barth, Richard J.; Kaufman, Peter A.; Paulsen, Keith D.

    2015-01-01

    The chaotic vascular network surrounding malignant tumors leads to pulsatile blood flow patterns that differ from those in benign regions of the breast. This study aimed to determine if high-speed electrical impedance tomography (EIT) is able to detect conductivity changes associated with cyclic blood-volume changes and to gauge the potential of using these signatures to differentiate malignant from benign regions within the breast. EIT imaging of pulsating latex membranes submerged in saline baths provided initial validation of its use for tracking temporally varying conductivities. Nineteen women (10 with cancer, nine without) were imaged with EIT over the course of several heartbeats in synchrony with pulse-oximetry acquisition. Eight parameters (rs, φ(rt,max), rt,max, Plow:full, Phigh:full, Plow:high) relating the conductivity images and pulse-oximeter signatures were extracted and used as a means of comparing malignant and benign regions of the breast. Significant differences (p < 0.01) between malignant and benign regions of interest were noted in seven of the eight parameters. The maximum correlation between conductivity and pulse-oximeter signals, rt,max, was observed to be the optimal discriminating parameter with a receiver operating characteristic area under the curve of 0.8 and a specificity of 81% at a sensitivity of 77%. Assessing the dynamic conductivity of breast may provide additional clinical utility to that of standard imaging modalities, but further investigation is necessary to better understand the biophysical mechanisms leading to the observed conductivity changes. PMID:25073168

  3. Enhanced absorption performance of carbon nanostructure based metamaterials and tuning impedance matching behavior by an external AC electric field.

    PubMed

    Gholipur, Reza; Khorshidi, Zahra; Bahari, Ali

    2017-03-27

    Metamaterials have surprisingly broadened the range of available practical applications in new devices such as shielding, microwave absorbing, and novel antenna. More researches are related to the tuning DNG frequency bands of ordered or disordered metamaterials, and far less research has focused on the importance of impedance matching behavior, and is not effort and attention in adjusting the magnitude of negative permittivity values. This is particularly important if devices deal with low amplitude signals such as radio or TV antenna. The carbon/hafnium nickel oxide (C/Hf0.9Ni0.1Oy) nanocomposites with simultaneously negative permittivity and negative permeability, excellent metamaterial performance and good impedance matching could become an efficient alternative for the ordered metamaterials in wave-transparent, microwave absorbing, and solar energy harvesting fields. In this study, we prepared C/Hf0.9Ni0.1Oy nanocomposites by solvothermal method, and we clarified how the impedance matching and double negative (DNG) behaviors of C/Hf0.9Ni0.1Oy can be tuned by an external AC electric field created by electric quadrupole system. External electric field allows for the alignment of the well-dispersed nanoparticles of carbon with long-range orientations order. We believe that this finding broadens our understanding of moderate conductive material-based random metamaterials (MCMRMs), and provides a novel strategy for replacing high loss ordered or disordered metamaterials with MCMRMs.

  4. System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography

    PubMed Central

    Aguiar Santos, Susana; Robens, Anne; Boehm, Anna; Leonhardt, Steffen; Teichmann, Daniel

    2016-01-01

    A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz–960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images. PMID:27463715

  5. System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography.

    PubMed

    Aguiar Santos, Susana; Robens, Anne; Boehm, Anna; Leonhardt, Steffen; Teichmann, Daniel

    2016-07-25

    A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz-960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images.

  6. Setting ventilation parameters guided by electrical impedance tomography in an animal trial of acute respiratory distress syndrome

    NASA Astrophysics Data System (ADS)

    Czaplik, Michael; Biener, Ingeborg; Leonhardt, Steffen; Rossaint, Rolf

    2014-03-01

    Since mechanical ventilation can cause harm to lung tissue it should be as protective as possible. Whereas numerous options exist to set ventilator parameters, an adequate monitoring is lacking up to date. The Electrical Impedance Tomography (EIT) provides a non-invasive visualization of ventilation which is relatively easy to apply and commercially available. Although there are a number of published measures and parameters derived from EIT, it is not clear how to use EIT to improve clinical outcome of e.g. patients suffering from acute respiratory distress syndrome (ARDS), a severe disease with a high mortality rate. On the one hand, parameters should be easy to obtain, on the other hand clinical algorithms should consider them to optimize ventilator settings. The so called Global inhomogeneity (GI) index bases on the fact that ARDS is characterized by an inhomogeneous injury pattern. By applying positive endexpiratory pressures (PEEP), homogeneity should be attained. In this study, ARDS was induced by a double hit procedure in six pigs. They were randomly assigned to either the EIT or the control group. Whereas in the control group the ARDS network table was used to set the PEEP according to the current inspiratory oxygen fraction, in the EIT group the GI index was calculated during a decremental PEEP trial. PEEP was kept when GI index was lowest. Interestingly, PEEP was significantly higher in the EIT group. Additionally, two of these animals died ahead of the schedule. Obviously, not only homogeneity of ventilation distribution matters but also limitation of over-distension.

  7. Poster — Thur Eve — 09: Evaluation of electrical impedance and computed tomography fusion algorithms using an anthropomorphic phantom

    SciTech Connect

    Chugh, Brige Paul; Krishnan, Kalpagam; Liu, Jeff; Kohli, Kirpal

    2014-08-15

    Integration of biological conductivity information provided by Electrical Impedance Tomography (EIT) with anatomical information provided by Computed Tomography (CT) imaging could improve the ability to characterize tissues in clinical applications. In this paper, we report results of our study which compared the fusion of EIT with CT using three different image fusion algorithms, namely: weighted averaging, wavelet fusion, and ROI indexing. The ROI indexing method of fusion involves segmenting the regions of interest from the CT image and replacing the pixels with the pixels of the EIT image. The three algorithms were applied to a CT and EIT image of an anthropomorphic phantom, constructed out of five acrylic contrast targets with varying diameter embedded in a base of gelatin bolus. The imaging performance was assessed using Detectability and Structural Similarity Index Measure (SSIM). Wavelet fusion and ROI-indexing resulted in lower Detectability (by 35% and 47%, respectively) yet higher SSIM (by 66% and 73%, respectively) than weighted averaging. Our results suggest that wavelet fusion and ROI-indexing yielded more consistent and optimal fusion performance than weighted averaging.

  8. Measurement of Peak Esophageal Luminal Cross Sectional Area Utilizing Nadir Intraluminal Impedance

    PubMed Central

    Zifan, Ali; Ledgerwood-Lee, Melissa; Mittal, Ravinder K

    2015-01-01

    BACKGROUND Multichannel intraluminal impedance (MII) is currently used to monitor gastroesophageal reflux and esophageal bolus clearance. We describe a novel methodology to measure maximal luminal CSA during bolus transport from MII measurements. METHODS Studies were conducted in-vitro (test tubes) and in-vivo (healthy subjects). Concurrent MII, HRM, and intraluminal ultrasound (US) were recorded 7 cm above the lower esophageal sphincter. Swallows with two concentrations of saline, 0.1N and 0.5N, of bolus volumes 5cc, 10cc and 15cc were performed. The CSA was estimated by solving two algebraic Ohm’s law equations, resulting from the two saline solutions. The CSA calculated from impedance method was compared with the CSA measured from the intraluminal US images. KEY RESULTS The CSA measured in duplicate from B-mode US images showed a mean difference between the two manual delineations to be near zero, and the repeatability coefficient was within 7.7% of the mean of the two CSA measurements. The calculated CSA from the impedance measurements strongly correlated with the US measured CSA (R2 ≅ 0.98). A detailed statistical analysis of the impedance and US measured CSA data indicated that the 95% limits of agreement between the two methods ranged from −9.1 to 13mm2. The root mean square error (RMS) of the two measurements was 4.8% of the mean US-measured CSA. CONCLUSIONS We describe a novel methodology to measure peak esophageal luminal CSA during peristalsis. Further studies are needed to determine if it is possible to measure patterns of luminal distension during peristalsis across the entire length of the esophagus. PMID:25930157

  9. Bench-Top Impedance Measurements for a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade

    SciTech Connect

    Smith, Jeffrey Claiborne; Bane, Karl; Doyle, Eric; Keller, Lew; Lundgren, Steve; Markiewicz, Tom; Ng, Cho-Kuen; Xiao, Liling; /SLAC

    2010-08-26

    Simulations have been performed in Omega3P to study both trapped modes and impedance contributions of a rotatable collimator for the LHC phase II collimation upgrade. Bench-top stretched coil probe impedance methods are also being implemented for measurements on prototype components to directly measure the low frequency impedance contributions. The collimator design also calls for a RF contact interface at both jaw ends with contact resistance much less than a milliohm in order to limit transverse impedance. DC resistance measurements in a custom built test chamber have been performed to test the performance of this interface.

  10. Error correction algorithm for high accuracy bio-impedance measurement in wearable healthcare applications.

    PubMed

    Kubendran, Rajkumar; Lee, Seulki; Mitra, Srinjoy; Yazicioglu, Refet Firat

    2014-04-01

    Implantable and ambulatory measurement of physiological signals such as Bio-impedance using miniature biomedical devices needs careful tradeoff between limited power budget, measurement accuracy and complexity of implementation. This paper addresses this tradeoff through an extensive analysis of different stimulation and demodulation techniques for accurate Bio-impedance measurement. Three cases are considered for rigorous analysis of a generic impedance model, with multiple poles, which is stimulated using a square/sinusoidal current and demodulated using square/sinusoidal clock. For each case, the error in determining pole parameters (resistance and capacitance) is derived and compared. An error correction algorithm is proposed for square wave demodulation which reduces the peak estimation error from 9.3% to 1.3% for a simple tissue model. Simulation results in Matlab using ideal RC values show an average accuracy of for single pole and for two pole RC networks. Measurements using ideal components for a single pole model gives an overall and readings from saline phantom solution (primarily resistive) gives an . A Figure of Merit is derived based on ability to accurately resolve multiple poles in unknown impedance with minimal measurement points per decade, for given frequency range and supply current budget. This analysis is used to arrive at an optimal tradeoff between accuracy and power. Results indicate that the algorithm is generic and can be used for any application that involves resolving poles of an unknown impedance. It can be implemented as a post-processing technique for error correction or even incorporated into wearable signal monitoring ICs.

  11. Method and device for bio-impedance measurement with hard-tissue applications.

    PubMed

    Guimerà, A; Calderón, E; Los, P; Christie, A M

    2008-06-01

    Bio-impedance measurements can be used to detect and monitor several properties of living hard-tissues, some of which include bone mineral density, bone fracture healing or dental caries detection. In this paper a simple method and hardware architecture for hard tissue bio-impedance measurement is proposed. The key design aspects of such architecture are discussed and a commercial handheld ac impedance device is presented that is fully certified to international medical standards. It includes a 4-channel multiplexer and is capable of measuring impedances from 10 kOmega to 10 MOmega across a frequency range of 100 Hz to 100 kHz with a maximum error of 5%. The device incorporates several user interface methods and a Bluetooth link for bi-directional wireless data transfer. Low-power design techniques have been implemented, ensuring the device exceeds 8 h of continuous use. Finally, bench test results using dummy cells consisting of parallel connected resistors and capacitors, from 10 kOmega to 10 MOmega and from 20 pF to 100 pF, are discussed.

  12. End-point impedance measurements across dominant and nondominant hands and robotic assistance with directional damping.

    PubMed

    Erden, Mustafa Suphi; Billard, Aude

    2015-06-01

    The goal of this paper is to perform end-point impedance measurements across dominant and nondominant hands while doing airbrush painting and to use the results for developing a robotic assistance scheme. We study airbrush painting because it resembles in many ways manual welding, a standard industrial task. The experiments are performed with the 7 degrees of freedom KUKA lightweight robot arm. The robot is controlled in admittance using a force sensor attached at the end-point, so as to act as a free-mass and be passively guided by the human. For impedance measurements, a set of nine subjects perform 12 repetitions of airbrush painting, drawing a straight-line on a cartoon horizontally placed on a table, while passively moving the airbrush mounted on the robot's end-point. We measure hand impedance during the painting task by generating sudden and brief external forces with the robot. The results show that on average the dominant hand displays larger impedance than the nondominant in the directions perpendicular to the painting line. We find the most significant difference in the damping values in these directions. Based on this observation, we develop a "directional damping" scheme for robotic assistance and conduct a pilot study with 12 subjects to contrast airbrush painting with and without robotic assistance. Results show significant improvement in precision with both dominant and nondominant hands when using robotic assistance.

  13. Application of a coaxial-like sensor for impedance spectroscopy measurements of selected low-conductivity liquids.

    PubMed

    Szypłowska, Agnieszka; Nakonieczna, Anna; Wilczek, Andrzej; Paszkowski, Bartosz; Solecki, Grzegorz; Skierucha, Wojciech

    2013-09-30

    The paper presents a coaxial-like sensor operating in the 20 Hz-2 MHz frequency range used to determine the electrical properties of selected liquids of low electrical conductivity. Examined materials included low-concentrated aqueous solutions of potassium chloride, sodium chloride and trisodium citrate, which are common food additives. Impedance spectra of the measurement cell filled with particular liquids were obtained and analyzed using the electrical equivalent circuit approach. The values of physical quantities and parameters describing the equivalent circuit components, including a constant phase element, were calculated for each sample. The applied sensor was also calibrated for electrical conductivity measurements up to 8 mS/m. The constant phase element parameters differed among the studied solutions and concentrations. This may provide a basis for a detection method of small amounts of compounds, such as food additives in low-concentrated aqueous solutions. To demonstrate the potential of the presented method, samples of purchased mineral water and a flavored drink containing various additives were tested.

  14. Application of a Coaxial-Like Sensor for Impedance Spectroscopy Measurements of Selected Low-Conductivity Liquids

    PubMed Central

    Szypłowska, Agnieszka; Nakonieczna, Anna; Wilczek, Andrzej; Paszkowski, Bartosz; Solecki, Grzegorz; Skierucha, Wojciech

    2013-01-01

    The paper presents a coaxial-like sensor operating in the 20 Hz–2 MHz frequency range used to determine the electrical properties of selected liquids of low electrical conductivity. Examined materials included low-concentrated aqueous solutions of potassium chloride, sodium chloride and trisodium citrate, which are common food additives. Impedance spectra of the measurement cell filled with particular liquids were obtained and analyzed using the electrical equivalent circuit approach. The values of physical quantities and parameters describing the equivalent circuit components, including a constant phase element, were calculated for each sample. The applied sensor was also calibrated for electrical conductivity measurements up to 8 mS/m. The constant phase element parameters differed among the studied solutions and concentrations. This may provide a basis for a detection method of small amounts of compounds, such as food additives in low-concentrated aqueous solutions. To demonstrate the potential of the presented method, samples of purchased mineral water and a flavored drink containing various additives were tested. PMID:24084120

  15. Measurement of respiratory impedance by impulse oscillometry--effects of endotracheal tubes.

    PubMed

    Kuhnle, G E; Brandt, T; Roth, U; Goetz, A E; Smith, H J; Peter, K

    2000-12-01

    Impulse Oscillometry is a new, noninvasive method to measure respiratory impedance, i.e. airway resistance and reactance at different oscillation frequencies. These parameters are potentially useful for the monitoring of respiratory mechanics in the critically ill patent with respiratory dysfunction. The endotracheal tube, used to mechanically ventilate these patients, however, represents an additional nonlinear impedance that introduces artifacts into the measurements. The objective of this work was therefore to investigate the effects of clinically available endotracheal tubes on resistance and reactance of an in vitro analogue of the respiratory system. Additionally, the effects of decreasing the compressible gas volume in this experimental model, as a simulation of decreased lung capacity and compliance, was investigated. Impulse oscillometric measurements of the test analogue gave highly reproducible results with and without an endotracheal tube. The tubes had significant influence on the measurement of the test object at all frequencies investigated. Changes of low frequent reactance were negligible - at least if repetitive measurements of the same system are performed - for realistic measurement of airway resistance, a correction of the tube impedance or measurement of the pressure distal of the tube is required. Resistance increased and low frequent reactance decreased significantly with decreasing gas volume. These changes were of magnitudes higher than the variations due to the introduction of the endotracheal tubes. Our results suggest that changes of respiratory reactance measured with impulse oscillometry may be used as a monitoring parameter in intubated patients.

  16. Measurements of Middle Ear Pressure Gain and Cochlear Input Impedance in the Chinchilla

    NASA Astrophysics Data System (ADS)

    Slama, Michael C. C.; Ravicz, Michael E.; Nakajima, Hideko H.; Dong, Wei; Rosowski, John J.

    2009-02-01

    Measurements of middle ear conducted sound pressure in the cochlear vestibule PV have been performed in only a few species. Simultaneous measurements of sound-induced stapes velocity Vs are even more rare. We report simultaneous measurements of VS and PV in chinchillas. The VS measurements are performed using single-beam laser-Doppler vibrometry; PV is measured with fiber-optic pressure sensors like those described by Olson [1]. PV and VS have been measured in six animals, and the middle ear pressure gain (ratio of PV to the sound pressure in the ear canal) and the cochlear input impedance (ratio of PV to the product of VS and area of the footplate) computed. Our measurements of middle ear pressure gain are similar to published data in the chinchilla at stimulus frequencies of 500 Hz to 3 kHz, but are different at other frequencies. Our measurements of cochlear input impedance differ somewhat from previous estimates in the chinchilla and show a resistive input impedance up to at least 10 kHz.

  17. Comparison of impedance cardiography and dye dilution method for measuring cardiac output

    PubMed Central

    Spiering, W; van Es, P N; de Leeuw, P W

    1998-01-01

    Objective—To assess the degree of agreement between impedance cardiography, using the NCCOM3-R7 device, and the gold standard—the dye dilution method—both under basal conditions and after stimulation of cardiac output.
Patients—35 paired measurements in five healthy male volunteers.
Interventions—To obtain higher levels of cardiac output, cardiac performance was stimulated with a dopamine infusion.
Results—In 35 paired measurements, the mean of all the impedance values was higher than that of the dye dilution values, at 10.2 v 7.4 l/min (p < 0.0001). The mean discrepancy between the two methods was 3.3 l/min, and the mean bias −2.9 l/min, with limits of agreement of −9.0 and 3.2 l/min. A change in cardiac output could not adequately be predicted by the NCCOM3-R7. In 20 of 25 measurements obtained during continuous intravenous dopamine infusions there was a rise in dye dilution cardiac output (range 0.2 to 5.9 l/min). Neither the magnitude nor the direction of the change in dye dilution values corresponded with the change measured by impedance cardiography. The mean discrepancy here between the two methods was 1.8 l/min, and the mean bias −0.8 l/min, with limits of agreement of −4.9 and 3.3 l/min.
Conclusions—In healthy volunteers, impedance cardiography with NCCOM3-R7 is inadequate for assessing cardiac output when compared with the dye dilution method.

 Keywords: cardiac output;  impedance cardiography;  dye dilution PMID:9659188

  18. Wire Measurement of Impedance of an X-Band Accelerating Structure

    SciTech Connect

    Baboi, N

    2004-09-02

    Several tens of thousands of accelerator structures will be needed for the next generation of normal conducting linear colliders known as the GLC/NLC (Global Linear Collider/Next Linear Collider). To prevent the beam being driven into a disruptive BBU (Beam Break-Up) mode or at the very least, the emittance being significantly diluted, it is important to damp down the wakefield left by driving bunches to a manageable level. Manufacturing errors and errors in design need to be measured and compared with prediction. In this paper a bench-top method of measuring transverse impedances in X-band accelerating structures is described. Utilizing an off-axis wire the S parameters are measured and converted to impedance. Measurements in a damped and detuned structure built for GLC/NLC are presented and the results are discussed.

  19. Battery-powered portable instrument system for single-cell trapping, impedance measurements, and modeling analyses.

    PubMed

    Tsai, Sung-Lin; Chiang, Yang; Wang, Min-Haw; Chen, Ming-Kun; Jang, Ling-Sheng

    2014-08-01

    A battery-powered portable instrument system for the single-HeLa-cell trapping and analyses is developed. A method of alternating current electrothermal (ACET) and DEP are employed for the cell trapping and the method of impedance spectroscopy is employed for cell characterizations. The proposed instrument (160 mm × 170 mm × 110 mm, 1269 g) equips with a highly efficient energy-saving design that promises approximately 120 h of use. It includes an impedance analyzer performing an excitation voltage of 0.2-2 Vpp and a frequency sweep of 11-101 kHz, function generator with the sine wave output at an operating voltage of 1-50 Vpp with a frequency of 4-12 MHz, cell-trapping biochip, microscope, and input/output interface. The biochip for the single cell trapping is designed and simulated based on a combination of ACET and DEP forces. In order to improve measurement accuracy, the curve fitting method is adopted to calibrate the proposed impedance spectroscopy. Measurement results from the proposed system are compared with results from a precision impedance analyzer. The trapped cell can be modeled for numerical analyses. Many advantages are offered in the proposed instrument such as the small volume, real-time monitoring, rapid analysis, low cost, low-power consumption, and portable application.

  20. Impedance Measurements as a Tool for the Detection of Endocrine Disrupting Chemicals

    DTIC Science & Technology

    2007-11-02

    endocrine disruptors on human health has created a need for screening systems to detect xenoestrogens, a diverse group of chemicals that mimic...Impedance Measurements as a Tool for the Detection of Endocrine Disrupting Chemicals V. Sacks, J. Rishpon* Department of Molecular...sensitive and amenable to use on-site, providing an efficient and economic tool for measuring minuscule amounts of endocrine disrupting chemicals

  1. Feature-space assessment of electrical impedance tomography coregistered with computed tomography in detecting multiple contrast targets

    SciTech Connect

    Krishnan, Kalpagam; Liu, Jeff; Kohli, Kirpal

    2014-06-15

    Purpose: Fusion of electrical impedance tomography (EIT) with computed tomography (CT) can be useful as a clinical tool for providing additional physiological information about tissues, but requires suitable fusion algorithms and validation procedures. This work explores the feasibility of fusing EIT and CT images using an algorithm for coregistration. The imaging performance is validated through feature space assessment on phantom contrast targets. Methods: EIT data were acquired by scanning a phantom using a circuit, configured for injecting current through 16 electrodes, placed around the phantom. A conductivity image of the phantom was obtained from the data using electrical impedance and diffuse optical tomography reconstruction software (EIDORS). A CT image of the phantom was also acquired. The EIT and CT images were fused using a region of interest (ROI) coregistration fusion algorithm. Phantom imaging experiments were carried out on objects of different contrasts, sizes, and positions. The conductive medium of the phantoms was made of a tissue-mimicking bolus material that is routinely used in clinical radiation therapy settings. To validate the imaging performance in detecting different contrasts, the ROI of the phantom was filled with distilled water and normal saline. Spatially separated cylindrical objects of different sizes were used for validating the imaging performance in multiple target detection. Analyses of the CT, EIT and the EIT/CT phantom images were carried out based on the variations of contrast, correlation, energy, and homogeneity, using a gray level co-occurrence matrix (GLCM). A reference image of the phantom was simulated using EIDORS, and the performances of the CT and EIT imaging systems were evaluated and compared against the performance of the EIT/CT system using various feature metrics, detectability, and structural similarity index measures. Results: In detecting distilled and normal saline water in bolus medium, EIT as a stand

  2. Behaviour of the electrical impedance myography in isometric contraction of biceps brachii at different elbow joint angles

    NASA Astrophysics Data System (ADS)

    Coutinho, A. B. B.; Jotta, B.; Pino, A. V.; Souza, M. N.

    2012-12-01

    Electrical impedance myography (EIM) can be understood as an experimental technique applied to evaluate bioelectrical impedance associated to the muscular activity. With the development of technique, some studies are trying to associate the EIM parameters with the morphological and physiological changes that occur in the muscle during contraction. In this context this work sought to associate EIM parameters observed during isometric contractions of the biceps brachii muscle at different elbow joint angles with the correspondent muscular force. Differently from previous works that did not observe significant correlation between those data, our findings point to high correlations between the some EIM resistive parameters and the muscle force. Despite the need of further investigation, our results indicated that EIM technique can be used to estimate muscle force in a noninvasive way.

  3. A compact wideband precision impedance measurement system based on digital auto-balancing bridge

    NASA Astrophysics Data System (ADS)

    Hu, Binxin; Wang, Jinyu; Song, Guangdong; Zhang, Faxiang

    2016-05-01

    The ac impedance spectroscopy measurements are predominantly taken by using impedance analyzers based on analog auto-balancing bridge. However, those bench-top analyzers are generally complicated, bulky and expensive, thus limiting their usage in industrial field applications. This paper presents the development of a compact wideband precision measurement system based on digital auto-balancing bridge. The methods of digital auto-balancing bridge and digital lock-in amplifier are analyzed theoretically. The overall design and several key sections including null detector, direct digital synthesizer-based sampling clock, and digital control unit are introduced in detail. The results show that the system achieves a basic measurement accuracy of 0.05% with a frequency range of 20 Hz-2 MHz. The advantages of versatile measurement capacity, fast measurement speed, small size and low cost make it quite suitable for industrial field applications. It is demonstrated that this system is practical and effective by applying in determining the impedance-temperature characteristic of a motor starter PTC thermistor.

  4. New Opportunities for Fracture Healing Detection: Impedance Spectroscopy Measurements Correlate to Tissue Composition in Fractures.

    PubMed

    Lin, Monica C; Yang, Frank; Herfat, Safa T; Bahney, Chelsea S; Marmor, Meir; Maharbiz, Michel M

    2017-04-06

    Accurate evaluation of fracture healing is important for clinical decisions on when to begin weight-bearing and when early intervention is necessary in cases of fracture nonunion. While the stages of healing involving hematoma, cartilage, trabecular bone, and cortical bone have been well characterized histologically, physicians typically track fracture healing by using subjective physical examinations and radiographic techniques that are only able to detect mineralized stages of bone healing. This exposes the need for a quantitative, reliable technique to monitor fracture healing, and particularly to track healing progression during the early stages of repair. The goal of this study was to validate the use of impedance spectroscopy to monitor fracture healing and perform comprehensive evaluation comparing measurements with histological evidence. Here we show that impedance spectroscopy not only can distinguish between cadaver tissues involved throughout fracture repair, but also correlates to fracture callus composition over the middle stages of healing in wild-type C57BL/6 mice. Specifically, impedance magnitude has a positive relationship with % trabecular bone and a negative relationship with % cartilage, and the opposite relationships are found when comparing phase angle to these same volume fractions of tissues. With this information, we can quantitatively evaluate how far a fracture has progressed through the healing stages. Our results demonstrate the feasibility of impedance spectroscopy for detection of fracture callus composition and reveals its potential as a method for early detection of bone healing and fracture nonunion. This article is protected by copyright. All rights reserved.

  5. Towards the development of a wearable Electrical Impedance Tomography system: A study about the suitability of a low power bioimpedance front-end.

    PubMed

    Menolotto, Matteo; Rossi, Stefano; Dario, Paolo; Della Torre, Luigi

    2015-01-01

    Wearable systems for remote monitoring of physiological parameter are ready to evolve towards wearable imaging systems. The Electrical Impedance Tomography (EIT) allows the non-invasive investigation of the internal body structure. The characteristics of this low-resolution and low-cost technique match perfectly with the concept of a wearable imaging device. On the other hand low power consumption, which is a mandatory requirement for wearable systems, is not usually discussed for standard EIT applications. In this work a previously developed low power architecture for a wearable bioimpedance sensor is applied to EIT acquisition and reconstruction, to evaluate the impact on the image of the limited signal to noise ratio (SNR), caused by low power design. Some anatomical models of the chest, with increasing geometric complexity, were developed, in order to evaluate and calibrate, through simulations, the parameters of the reconstruction algorithms provided by Electrical Impedance Diffuse Optical Reconstruction Software (EIDORS) project. The simulation results were compared with experimental measurements taken with our bioimpedance device on a phantom reproducing chest tissues properties. The comparison was both qualitative and quantitative through the application of suitable figures of merit; in this way the impact of the noise of the low power front-end on the image quality was assessed. The comparison between simulation and measurement results demonstrated that, despite the limited SNR, the device is accurate enough to be used for the development of an EIT based imaging wearable system.

  6. Intracranial Electrical Impedance Tomography: A Method of Continuous Monitoring in an Animal Model of Head Trauma

    PubMed Central

    Manwaring, Preston K.; Moodie, Karen L.; Hartov, Alexander; Manwaring, Kim H.; Halter, Ryan J.

    2013-01-01

    Background Electrical impedance tomography (EIT) is a method that can render continuous graphical cross-sectional images of the brain’s electrical properties. Because these properties can be altered by variations in water content, shifts in Na+ concentration, bleeding, and mass deformation, EIT has promise as a sensitive instrument for head injury monitoring to improve early recognition of deterioration, and to observe the benefits of therapeutic intervention. This study presents a swine model of head injury used to determine the detection capabilities of an inexpensive bed side EIT monitoring system with a novel intracranial pressure (ICP)/EIT electrode combination sensor on induced intraparenchymal mass effect, intraparenchymal hemorrhage, and cessation of brain blood flow. Conductivity difference images are shown in conjunction with ICP data, confirming the effects. Methods Eight domestic piglets (3–4 weeks old, mean 10kg), under general anesthesia, were subjected to four injuries: induced intraparenchymal mass effect using an inflated, and later, deflated 0.15mL Fogarty catheter; hemorrhage by intraparenchymal injection of 1mL arterial blood; and ischemia/infarction by euthanasia. EIT and ICP data were recorded 10 minutes prior to inducing the injury until 10 minutes post-injury. Continuous EIT and ICP monitoring were facilitated by a ring of circumferentially disposed cranial Ag/AgCl electrodes and one intraparenchymal ICP/EIT sensor-electrode combination. Data were recorded at 100 Hz. Two-dimensional tomographic conductivity difference (Δσ) images, rendered using data before and after an injury, were displayed in real-time on an axial circular mesh. Regions of interest (ROI) within the images were automatically selected as the upper or lower 5% of conductivity data depending upon the nature of the injury. Mean Δσ within the ROIs and background were statistically analyzed. ROI Δσ was compared to the background Δσ after an injury event using an

  7. TECHNICAL NOTE: Portable audio electronics for impedance-based measurements in microfluidics

    NASA Astrophysics Data System (ADS)

    Wood, Paul; Sinton, David

    2010-08-01

    We demonstrate the use of audio electronics-based signals to perform on-chip electrochemical measurements. Cell phones and portable music players are examples of consumer electronics that are easily operated and are ubiquitous worldwide. Audio output (play) and input (record) signals are voltage based and contain frequency and amplitude information. A cell phone, laptop soundcard and two compact audio players are compared with respect to frequency response; the laptop soundcard provides the most uniform frequency response, while the cell phone performance is found to be insufficient. The audio signals in the common portable music players and laptop soundcard operate in the range of 20 Hz to 20 kHz and are found to be applicable, as voltage input and output signals, to impedance-based electrochemical measurements in microfluidic systems. Validated impedance-based measurements of concentration (0.1-50 mM), flow rate (2-120 µL min-1) and particle detection (32 µm diameter) are demonstrated. The prevailing, lossless, wave audio file format is found to be suitable for data transmission to and from external sources, such as a centralized lab, and the cost of all hardware (in addition to audio devices) is ~10 USD. The utility demonstrated here, in combination with the ubiquitous nature of portable audio electronics, presents new opportunities for impedance-based measurements in portable microfluidic systems.

  8. Long-term measurement of impedance in chronically implanted depth and subdural electrodes during responsive neurostimulation in humans.

    PubMed

    Sillay, Karl A; Rutecki, Paul; Cicora, Kathy; Worrell, Greg; Drazkowski, Joseph; Shih, Jerry J; Sharan, Ashwini D; Morrell, Martha J; Williams, Justin; Wingeier, Brett

    2013-09-01

    Long-term stability of the electrode-tissue interface may be required to maintain optimal neural recording with subdural and deep brain implants and to permit appropriate delivery of neuromodulation therapy. Although short-term changes in impedance at the electrode-tissue interface are known to occur, long-term changes in impedance have not previously been examined in detail in humans. To provide further information about short- and long-term impedance changes in chronically implanted electrodes, a dataset from 191 persons with medicall