OBJECTIVETo study the data characteristics of dielectric properties of normal blood cells.

METHODSThe AC impedances of blood samples from the 30 healthy volunteers were measured with impedance analyzer at the radio frequency range, and its frequency properties were assess in view of the dielectric spectroscopy, complex plots, loss factor, imaginary part of conductivity and loss tangent.

RESULTSThe permittivity and conductivity of healthy adult whole blood cells had a dependence of frequency. The dielectric properties of human blood cells had two characteristic frequencies at 0.59 MHz and 2.12 MHz.

CONCLUSIONThe frequency properties of blood cells can be obtained by impedance analysis within the frequency range.

Adult ; Blood Cells ; physiology ; Electric Conductivity ; Electric Impedance ; Humans

The dielectric spectroscopy of human platelets was measured within the frequency range of 100 KHz-100 MHz, and the dielectric numerical characters of human platelets in response to AC electric field were analyzed. We measured the AC impedance of normal human platelets with the impedance technique in the frequency domain for the first time. The experimental data were used to draw a relationship curve between the frequency of electric field and permittivity or conductivity, and then the dielectric spectrum and the Cole-Cole plots of human platelets were established and then, the characteristics of dielectric response of human platelets were decided, which demonstrated the dependence of permittivity and conductivity of human platelets upon frequency, and showed two characteristic frequencies of the dielectric spectroscopy of human platelets: the first characteristic frequency f(C1) = 6.66 MHz; the second characteristic frequency f(C2) = 9.81 MHz.
Blood Platelets ; cytology ; physiology ; Electric Conductivity ; Electric Impedance ; Electrochemistry ; methods ; Electrophysiology ; Humans ; Spectrum Analysis ; methods

OBJECTIVETo establish characteristic parameters of complex impedance spectrum of rabbit whole blood cells.

METHODSThe AC impedances of 30 blood samples from the 10 rabbits were measured with the Agilent 4294A impedance analyzer at frequency range of 0.01-100 MHz and its characteristic data were analyzed by the Bode plot, the Nyquist plot and the Nichols plot.

RESULTSThe impedance amplitude and phase angle of rabbit blood cells was frequency-dependent. The impedance spectrum of rabbit blood cells had two characteristic frequencies: the 1st one (f(C1)) was 2.58 MHz, the 2nd one (f(C2)) was 5.21 MHz.

CONCLUSIONThe frequency properties of whole blood cells can be obtained by the analysis of impedance spectrum.

Animals ; Blood Cells ; cytology ; physiology ; Electric Conductivity ; Electric Impedance ; Rabbits ; Spectrum Analysis ; methods

The conductivity and permittivity of blood in mice were measured by the AC electrical impedance method at frequency range of 0.1-100MHz, and then the changes of the Cole-Cole parameters of dielectric spectra of blood from phenylhydrazine-induced anemia mice were observed by numerical calculation and curve fitting residual analysis of the Cole-Cole equation. The results showed that hematocrit (Hct) of the mice with phenylhydrazine injection was significantly reduced; the permittivity(epsilon) spectroscopy of blood moved to the low insulating region and its permittivity decreased; conductivity (kappa) spectrum curve of blood moved to the high conductivity zone and conductivity increased; the 2nd characteristic frequency was lower than that in the normal group. There was phenylhydrazine dose dependent in the changes of the Cole-Cole parameters of dielectric spectra of blood.
Anemia ; blood ; Animals ; Blood Physiological Phenomena ; Electric Conductivity ; Electric Impedance ; Hematocrit ; Mice

PURPOSE: To realistically map the electric fields of biological tissues using a diffusion tensor magnetic resonance electrical impedance tomography (DT-MREIT) method to estimate tissue response during electrical stimulation. METHODS: Imaging experiments were performed using chunks of bovine muscle. Two silver wire electrodes were positioned inside the muscle tissue for electrical stimulation. Electric pulses were applied with a 100-V amplitude and 100-μs width using a voltage stimulator. During electrical stimulation, we collected DT-MREIT data from a 3T magnetic resonance imaging scanner. We adopted the projected current density method to calculate the electric field. Based on the relation between the water diffusion tensor and the conductivity tensor, we computed the position-dependent scale factor using the measured magnetic flux density data. Then, a final conductivity tensor map was reconstructed using the multiplication of the water diffusion tensor and the scale factor. RESULTS: The current density images from DT-MREIT data represent the internal current flows that exist not only in the electrodes but also in surrounding regions. The reconstructed electric filed map from our anisotropic conductivity tensor with the projected current density shows coverage that is more than 2 times as wide, and higher signals in both the electrodes and surrounding tissues, than the previous isotropic method owing to the consideration of tissue anisotropy. CONCLUSIONS: An electric field map obtained by an anisotropic reconstruction method showed different patterns from the results of the previous isotropic reconstruction method. Since accurate electric field mapping is important to correctly estimate the coverage of the electrical treatment, future studies should include more rigorous validations of the new method through in vivo and in situ experiments.
Anisotropy ; Diffusion Tensor Imaging ; Diffusion* ; Electric Conductivity* ; Electric Impedance ; Electric Stimulation* ; Electrodes ; Magnetic Resonance Imaging ; Methods ; Silver ; Water*

In the research of tissue impedance spectroscopy measurement, the authors constructed a frequency sets that produce angularly equidistant points on the Nyquist loci. The studies of simulation data model demonstrate that, by use of the same quantity of frequency points and in comparison with the frequency sets that are logarithmic and quasi-linear, the angularly equidistant frequency sets can improve the estimate accuracy of tissue electrical model parameters of alpha and fc.
Biomedical Engineering ; Electric Conductivity ; Electric Impedance ; Humans ; Mathematics ; Models, Biological ; Signal Processing, Computer-Assisted ; Spectrum Analysis ; methods ; statistics & numerical data

Magnetic induction tomography (MIT) is a kind of novel imaging method. In this system, exciting coil directly affects the detection range and detection sensitivity. In order to improve eddy current inductive region magnetic field distribution, we established a 3D four layers homocentric sphere head model in this study. Then we carried out a 3D three dimensional transient finite element calculation in different coil radius, turns and line diameter of the exciting coil of MIT system. Then we analyzed the axial magnetic flux density of the eddy current inductive area and detected the coil induced voltage. The research results showed that the increased magnetic flux density, the augmented detection range and the improved detection sensitivity were all realized by enlarging radius, increasing line diameter and reducing turns.
Electric Conductivity ; Electric Impedance ; Image Processing, Computer-Assisted ; methods ; Imaging, Three-Dimensional ; methods ; Magnetic Fields ; Tomography ; methods

AIMTo study the changes in dielectric properties of gastrocnemius isolated from rats subjected to intermittent hypoxia for 4 weeks at the frequency range of 40 Hz - 110 MHz.

METHODSHypoxia was simulated by low-pressure chamber in male Sprague-Dawley rats, the rats were divided into two groups, that is, 4 weeks of intermittent hypoxia group and its control. The AC impedance of isolated gastrocnemius is measured with the Agilent 4294A impendance analyzer, and effects of intermittent hypoxia on dielectric properties of cells in isolated rat sural muscle were monitored by analyzing the dielectric numerical characters of the dielectric spectroscopy, the Cole-Cole plots, spectrum of loss factor and conductivity imaginary part, as well as loss tangent.

RESULTSIntermittent hypoxia could induce some changes, both relative permittivity (epsilon L, epsilon h) and permittivity increment deltaepsilon reduced, conductivity at low-frequency kappa L increased, conductivity at high-frequency kappa h reduced, and at the same time, the conductivity difference deltakappa also reduced. The characteristic frequency (f1, f2) increased. Peak of loss factor, the peak of conductivity imaginary part and the peak of loss tangent reduced.

CONCLUSIONFall in dielectric properties and increase in the characteristic frequency in skeletal muscle were induced by intermittent hypoxic acclimation.

Animals ; Electric Conductivity ; Electric Impedance ; Hypoxia ; physiopathology ; Male ; Muscle, Skeletal ; physiology ; Random Allocation ; Rats ; Rats, Sprague-Dawley

All-in-one adhesives were recently developed for reducing the techique sensitivity and chair time, but lots of concerns were made on bondability, longevity, and microleakage. The object of this study was to evaluate microleakage and marginal quality of all-in-one adhesives using electrochemical method and SEM analysis quantitatively. After making Class V cavities, they were bulk filled with Heliomolar(#A1) after surface treatment with three adhesives: Adper Prompt (Group A), One up bond F (Group O), Xeno III (Group X). Electrical conductivity (microamphere, microA) was checked two times: before and after cavity filling. Percentage of leaky margin was estimated from SEM image (x1,000). The data were statistically analysed: ANOVA and Paired T test for electrical conductivity, Kruskal-Wallis and Mann-Whitney test for marginal quality, Spearman's rho test for checking of relationships between 2 methods. The result were as follows: 1. There was no difference in microleakage between adhesive systems and every specimen showed some of microleakage after filling. 2. Microleakage was reduced about 70% with composite resin filling. 3. Marginal quality was the best in group A, decreasing among groups in the following order: group O, followed by group X. There were significant differences between group A and group X (p=0.015), and between group O and group X (p=0.019). 4. There was no relationship between the microleakage measured by electrochemical method and marginal quality measured by SEM analysis. Within the results of this study, there was no difference in microleakage among groups by electrical conductivity. However, significant difference in marginal quality was seen among groups. It was believed that these dissimilar results might be induced because of their own characteristics. Analysis of microleakage needs various methods for accuracy.
Adhesives* ; Electric Conductivity ; Longevity

OBJECTIVE: To investigate the sensing volume of open-ended coaxial probe technique for measurement of dielectric characteristics. METHODS: A measurement model combining macro- measurement device with a layer model of dielectric properties parameters was established for evaluating the sensing volume of open-ended coaxial probe technique. We defined sensing depth and sensing diameter to describe the distance that could be detected in vertical and horizontal direction. Using a variety of materials with different dielectric properties (Teflon, deionized water, ethanol, and gradient concentration sodium chloride solution), a layered model of dielectric properties differentiation was established. The total combined uncertainties (TCU) were calculated for different output power, and the output power was controlled to increase from -50 dBm to 15 dBm to calibrate the error range of the dielectric properties measurement system. The optimal output power range was determined based on the results of TCU test. In sensing volume measurement experiment, we set the control groups based on measurement parameters that potentially affect the sensing volume including output power (-10, -5, 0, 3, 6, and 9 dBm), frequency (1-500 MHz), Teflon, deionized water, and ethanol to form a dielectric constant difference between high and low contrast groups. Different concentrations of sodium chloride solution and Teflon were used to generate a conductivity difference between high and low contrast groups. These groups were tested in the sensing depth and sensing diameter measurement experiments. RESULTS: The result of TCU test indicated that accurate and stable measurement results could be obtained when the output power was greater or equal to-10 dBm (TCU < 2%). Sensing volume measurement experiment revealed a positive correlation between the sensing depth and output power ( < 0.05). As the measured power increased, the sensing depth gradually increased in deionized water and ethanol, and the difference reached 70 μm. The sensing depth was negatively correlated frequency ( < 0.05). As the concentration of sodium chloride solution increased, the corresponding sensing depth gradually decreased, with a difference reaching 270 μm. The sensing depth of high dielectric materials was greater than that pf low dielectric materials. The results of sensing diameter measurement were not obviously affected by the measurement parameters, and the sensing diameter was stable in a fixed range (1.0 to 1.8 mm) between the diameter of the inner conductor and the diameter of the insulation layer, and was less than the diameter of the probe. CONCLUSIONS The sensing volume of open-ended coaxial probe technique is affected by measurement parameters and dielectric properties of materials, which significantly affect the sensing depth.
Algorithms ; Electric Conductivity