Journal of Electrical Bioimpedance最新文献

The Cole-Cole model for a dielectric is a generalization of the Debye relaxation model. The most familiar form is in the frequency domain and this manifests itself in a frequency dependent impedance. Dielectrics may also be characterized in the time domain by means of the current and charge responses to a voltage step, called response and relaxation functions respectively. For the Debye model they are both exponentials while in the Cole-Cole model they are expressed by a generalization of the exponential, the Mittag-Leffler function. Its asymptotes are just as interesting and correspond to the Curie-von Schweidler current response which is known from real-life capacitors and the Kohlrausch stretched exponential charge response.

Physiological saline (0.9% NaCl) and deionized water were frozen in a laboratory chest freezer and impedance was monitored throughout freezing and thawing. The resistive and reactive components of electrical impedance were measured for these samples during freezing and thawing (heating) within a temperature range between 20 °C and -48 °C. The impedance of saline solution and de-ionized water increases sharply at the freezing point, similar to what is known for, e.g., complex tissues, including meat. Yet, only the saline solution impedance shows another sharp increment at a temperature between -30 and -20 °C. Changes of the electric properties after solidification suggest that the latter is linked to transformations of the ice lattice structure. We conclude that the electrical properties might serve as sensitive indicators of these phase changes.

Objective: Colposcopy can be used with Electrical Impedance Spectroscopy (EIS) as an adjunct, to assess the presence of High Grade Cervical Intra-epithelial Neoplasia (CIN2+). This analysis of longitudinal data has used the results from women with a negative colposcopy, in order to see if the initial (index) EIS results were able to predict the women who subsequently developed CIN2+. A further objective was to investigate what tissue structural changes might be reflected in the electrical impedance spectra.

Methods: 847 patients were referred with low grade cytologly. EIS measurements were made around the transformation zone of the cervix during colposcopy. Every EIS spectrum was matched to a template representing CIN2+ and the result was positive if the match exceeded a probability index threshold. The colposcopic impression was also recorded. All the women who developed biopsy proven CIN2+ within three years of the index colposcopy were identified.

Results: The median follow-up was 30.5 months. Where both CI and EIS were initially positive, there was an increased prevalence (8.13%) of CIN2+ developing as opposed to 3.45% in the remaining patients (p=0.0159). In addition, if three or more EIS spectra were positive there was a higher prevalence (9.62% as opposed to 3.56% p=0.0132) of CIN2+ at three years. The index spectra recorded from the women who developed CIN2+ showed EIS changes consistent with increases in the extracellular volume and in cell size inhomogeneity.

Conclusion: EIS does offer prognostic information on the risk of CIN2+ developing over the three-year period following the EIS measurements. The changes in EIS spectra are consistent with an increase in cell size diversity as pre-malignancy develops. These changes may be a consequence of increased genetic diversity as neoplasia develops.

The electrosurgical unit (ESU) is the most common device in modern surgery for cutting and coagulation of tissues. It produces high-frequency alternating current to prevent the stimulation of muscles and nerves. The commercial ESUs are generally expensive and their output power is uncontrolled. The main objective of the proposed study is to propose an economic ESU with an additional feature of output power regulation using a fuzzy logic controller (FLC) based proportional integral derivative (PID) tuned controller. Unlike the previous studies, the proposed controller is designed in a fully closed-loop control fashion to regulate the output power of the ESU to a fixed value under the consideration of highly dynamic tissue impedance. The performance of the proposed method is tested in the MATLAB/SIMULINK environment. In order to validate the superiority of the proposed method, a comparative analysis with a simple (PID) controller based ESU is presented.

Ventricular Assist Devices (VADs) are used to treat patients with cardiogenic shock. As the heart is unable to supply the organs with sufficient oxygenated blood and nutrients, a VAD maintains the circulation to keep the patient alive. The observation of the patient's hemodynamics is crucial for an individual treatment; therefore, sensors to measure quantifiable hemodynmaic parameters are desirable. In addition to pressure measurement, the volume of the left ventricle and the progress of muscle recovery seem to be promising parameters. Ongoing research aims to estimate ventricular volume and changes in electrical properties of cardiac muscle tissue by applying bioimpedance measurement. In the case where ventricular insufficiency is treated by a catheter-based VAD, this very catheter could be used to conduct bioimpedance measurement inside the assisted heart. However, the simultaneous measurement of bioimpedance and VAD support has not yet been realized, although this would allow the determination of various loading conditions of the ventricle. For this purpose, it is necessary to develop models to validate and quantify bioimpedance measurement during VAD support. In this study, we present an in silico and an in vitro conductivity model of a left ventricle to study the application of bioimpedance measurement in the context of VAD therapy. The in vitro model is developed from casting two anatomical silicone phantoms: One phantom of pure silicone, and one phantom enriched with carbon, to obtain a conductive behavior close to the properties of heart muscle tissue. Additionally, a measurement device to record the impedance inside the ventricle is presented. Equivalent to the in vitro model, the in silico model was designed. This finite element model offers changes in material properties for myocardium and the blood cavity. The measurements in the in vitro models show a strong correlation with the results of the simulation of the in silico model. The measurements and the simulation demonstrate a decrease in impedance, when conductive muscle properties are applied and higher impedances correspond to smaller ventricle cross sections. The in silico and in vitro models are used to further investigate the application of bioimpedance measurement inside the left heart ventricle during VAD support. We are confident that the models presented will allow for future evaluation of hemodynamic monitoring during VAD therapy at an early stage of research and development.

Designing proper frontend electronics is critical in the development of highly sophisticated electrode systems. Multielectrode arrays for measuring electrical signals or impedance require multichannel readout systems. Even more challenging is the differential or ratiometric configuration with simultaneous assessment of measurement and reference channels. In this work, an eight-channel frontend was developed for contacting a 2×8 electrode array (8 measurement and 8 reference electrodes) with a large common electrode to the impedance gain-phase analyzer Solartron 1260 (S-1260). Using the three independent and truly parallel monitor channels of the S-1260, impedance of trapped cells and reference material was measured at the same time, thereby considerably increasing the performance of the device. The frontend electronics buffers the generator output and applies a potentiostatic signal to the common electrode of the chip. The applied voltage is monitored using the current monitor of the S-1260 via voltage/current conversion. The frontend monitors the current through the electrodes and converts it to a voltage fed into the voltage monitors of the S-1260. For assessment of the 8 electrode pairs featured by the chip, a relay-based multiplexer was implemented. Extensive characterization and calibration of the frontend were carried out in a frequency range between 100 Hz and 1 MHz. Investigating the influence of the multiplexer and the frontend electronics, direct measurement with and without frontend was compared. Although differences were evident, they have been negligible below one per cent. The significance of measurement using the complex S-1260-frontend-electrode was tested using Kohlrausch's law. The impedance of an electrolytic dilution series was measured and compared to the theoretical values. The coincidence of measured values and theoretical prediction serves as an indicator for electrode sensitivity to cell behavior. Monitoring of cell behavior on the microelectrode surface will be shown as an example.

Skeletal muscle mass (SMM) plays an important role in health and physical performance. Its estimation is critical for the early detection of sarcopenia, a disease with high prevalence and high health costs. While multiple methods exist for estimating this body component, anthropometry and bioelectrical impedance analysis (BIA) are the most widely available in low- to middle-income countries. This study aimed to determine the correlation between muscle mass, estimated by anthropometry through measurement of calf circumference (CC) and skeletal mass index (SMI) by BIA. This was a cross-sectional and observational study that included 213 functional adults over 65 years of age living in the community. Measurements of height, weight, CC, and SMM estimated by BIA were made after the informed consent was signed. 124 women mean age 69.6 ± 3.1 years and 86 men mean age 69.5 ± 2.9 years had the complete data and were included in the analysis. A significant positive moderate correlation among CC and SMI measured by BIA was found (Pearson r= 0.57 and 0.60 for women and men respectively (p=0.0001)). A moderate significant correlation was found between the estimation of SMM by CC and by BIA. This suggests that CC could be used as a marker of sarcopenia for older adults in settings in lower-middle-income countries where no other methods of diagnosing muscle mass are available. Although the CC is not the unique parameter to the diagnosis of sarcopenia, it could be a useful procedure in the clinic to identify patients at risk of sarcopenia.

The development of biosensors to identify molecular markers or specific genes is fundamental for the implementation of new techniques that allow the detection of specific Deoxyribonucleic acid (DNA) sequences in a fast, economic and simple way. Different detection techniques have been proposed in the development of biosensors. Electrical Bioimpedance Spectroscopy (EBiS) has been used for diagnosis and monitoring of human pathologies, and is recognized as a safe, fast, reusable, easy and inexpensive technique. This study proves the development of a complementary DNA (cDNA) biosensor based on measurements of EBiS and DNA's immobilization with no chemical modifications. The evaluation of its potential utility in the detection of the gene expression of three inflammation characteristic biomarkers (NLRP3, IL-1β and Caspase 1) is presented. The obtained results demonstrate that EBiS can be used to identify different gene expression patterns, measurements that were validated by Quantitative Polymerase Chain Reaction (qPCR). These results indicate the technical feasibility for a biosensor of specific genes through bioimpedance measurements on the immobilization of cDNA.

There is a strong need for a non-invasive measurement technique that is capable of accurately identifying the physiological condition change or heterogeneity of subcutaneous adipose tissue (SAT) by localizing the abnormalities within the compartment. This paper aims to investigate the feasibility of Electrical Impedance Tomography (EIT) to assess the interstitial fluid in subcutaneous adipose tissue as an enhancement method of bioelectrical impedance spectroscopy (BIS). Here, we demonstrate the preliminary result of EIT with a wearable 16 electrodes sensor. The image-based reference EIT with fat weighted threshold method is proposed. In order to evaluate the performance of our novel method, a physiological swelling experiment is conducted, and Multi-Frequency Bioelectrical Impedance Analysis (MFBIA) is also applied as a comparison with EIT results. The experimental results showed that the proposed method was able to distinguish the physiological swelling condition and effectively to remove the unexpected background noise. Furthermore, the conductivity variation in the subcutaneous layer had a good correlation with extracellular water volume change from MFBIA data; the correlation coefficient R² = 0.927. It is concluded that the proposed method provides a significant prospect for SAT assessment.