Electrical Impedance Of Biological Tissues Research Articles

Early breast cancer detection and differentiation tool based on tissue impedance characteristics and machine learning.

During Basic screening, it is challenging, if not impossible to detect breast cancer especially in the earliest stage of tumor development. However, measuring the electrical impedance of biological tissue can detect abnormalities even before being palpable. Thus, we used impedance characteristics data of various breast tissue to develop a breast cancer screening tool guided and augmented by a deep learning (DL). A DL algorithm was trained to ideally classify six classes of breast cancer based on electrical impedance characteristics data of the breast tissue. The tool correctly predicted breast cancer in data of patients whose breast tissue impedance was reported to have been measured when other methods detected no anomaly in the tissue. Furthermore, a DL-based approach using Long Short-Term Memory (LSTM) effectively classified breast tissue with an accuracy of 96.67%. Thus, the DL algorithm and method we developed accurately augmented breast tissue classification using electrical impedance and enhanced the ability to detect and differentiate cancerous tissue in very early stages. However, more data and pre-clinical is required to improve the accuracy of this early breast cancer detection and differentiation tool.

Fatigue-Induced Cole Electrical Impedance Model Changes of Biceps Tissue Bioimpedance

Bioimpedance, or the electrical impedance of biological tissues, describes the passive electrical properties of these materials. To simplify bioimpedance datasets, fractional-order equivalent circuit presentations are often used, with the Cole-impedance model being one of the most widely used fractional-order circuits for this purpose. In this work, bioimpedance measurements from 10 kHz to 100 kHz were collected from participants biceps tissues immediately prior and immediately post completion of a fatiguing exercise protocol. The Cole-impedance parameters that best fit these datasets were determined using numerical optimization procedures, with relative errors of within approximately ± 0.5 % and ± 2 % for the simulated resistance and reactance compared to the experimental data. Comparison between the pre and post fatigue Cole-impedance parameters shows that the R ∞ , R 1 , and f p components exhibited statistically significant mean differences as a result of the fatigue induced changes in the study participants.

Toward a magnetic resonance electrical impedance tomography in ultra-low field: A direct magnetic resonance imaging method by an external alternating current

Measuring the electrical impedance of biological tissues in a low frequency range is challenging. Here, we have conducted a superconducting quantum interference device-based microtesla magnetic resonance (MR) imaging study. To obtain an MR image caused by an injected alternating current (ac), we utilized the direct resonance method in which the nuclear spins resonate with the ac magnetic field generated by the external ac current. This method requires an adiabatic pulse and non-adiabatic step-down pulse techniques. The experimental and simulation results agree well with each other and show the feasibility of low-frequency magnetic resonance electrical impedance tomography in the kHz range.

Variability of Cole-model bioimpedance parameters using magnitude-only measurements of apples from a two-electrode configuration

ABSTRACTElectrical impedance measurements have been widely researched to monitor physiological changes in fruits and vegetables in a nondestructive manner. Recently, the parameters of the Cole bioimpedance model (R0, R1, C, and α), an equivalent circuit that is widely used to represent the electrical impedance of biological tissues, were extracted using techniques without direct impedance measurements. In this study, the variability of the Cole parameters extracted from magnitude-only measurements (from 200 Hz to 1 MHz) of apples in a two-electrode setup was examined to understand the impact of electrode placement on the parameters evaluated using this technique. Eight electrodes were placed around the center latitudinal line of apples to collect seven sets of measurements from four different varieties (Granny Smith, Fuji, Red Delicious, and Spartan). The Cole impedance parameters were extracted in MATLAB from the collected measurements using a nonlinear least squares fitting method. These extractions indicated that the parameters R0 and R1 had the highest variability based on the electrode location, whereas the dispersion coefficient (α) had the lowest variability.

Determining the level of resection of the intestine in experimental acute intestinal obstruction using bioimpedance

Актуальность. Определение границ необратимого повреждения кишки в условиях острой кишечной непроходимости является одной из важнейших задач, выполняемых в ходе оперативного лечения данной патологии.Цель исследования: улучшение результатов хирургического лечения острой кишечной непроходимости путем уменьшения объема резекции кишки при ее некрозе.Материалы и методы. Исследование выполнено на 64 белых крысах линии «Вистар» массой 180-230 г. Под наркозом проводили срединную лапаротомию и моделировали острую странгуляционную тонкокишечную непроходимость путем наложения толстой лигатуры на петлю тонкой кишки (длиной 1,5-2 см) вместе с брыжейкой. Моделирование патологического процесса было произведено на сроки 1 час (n=11), 3 часа (n=13) и 6 часов (n=12). На 13 животных были исследованы показатели импеданса тонкой кишки в норме. Отдельную группу (n=15) составили животные, которым произведено моделирование острой кишечной непроходимости сроком на 3 часа с последующей резекцией кишки на различных уровнях и формированием кишечных анастомозов. Инвазивную биоимпедансометрию (БИМ) кишечной стенки производили с помощью устройства для измерения импеданса биологических тканей БИМ-II (Патент РФ №2366360). В качестве калибровки прибора перед исследованием in vitro измеряли импеданс физиологического раствора. Исследуемые участи кишки подвергались гистологическому исследованию.Результаты и их обсуждение. Величина импеданса физиологического раствора составила 0,46 кОм. При изучении изменений показателей БИМ приводящего и отводящего отделов тонкой кишки выявлено, что значения уменьшаются по направлению к зоне странгуляции, наиболее низкие величины регистрировались на границе с зоной странгуляции. По данным гистологического исследования тонкой кишки в зонах, где регистрировали показатели биоимпедансометрии ниже 2 кОм в условиях острой кишечной непроходимости, выявлены признаки некроза различной выраженности. При этом максимальное значение импеданса в этих участках было равно 1,99 кОм. В зонах кишки, где регистрировали показатели импеданса выше 2 кОм, независимо от сроков патологического процесса, признаков некроза обнаружено не было. При определении границ резекции кишки ориентиром служила величина импеданса выше 2 кОм.Гистологическое исследование кишечных анастомозов, выполненных при резекции кишки в условиях острой кишечной непроходимости с учетом данных биоимпедансометрии, и анастомозов, выполненных при резекции органа в пределах заведомо жизнеспособных тканей, не выявило существенных различий в гистоморфологической картине заживления.Выводы. Значение биоимпедансометрии участков приводящего и отводящего отделов кишки выше 2 кОм является критерием при определении границ резекции органа.Ключевые слова: эксперимент, острая кишечная непроходимость, жизнеспособность кишки, биоимпедансометрия.

Solving the forward problem of magnetoacoustic tomography with magnetic induction by means of the finite element method

Magnetoacoustic tomography with magnetic induction (MAT-MI) is a recently proposed imaging modality to image the electrical impedance of biological tissue. It combines the good contrast of electrical impedance tomography with the high spatial resolution of sonography. In this paper, a three-dimensional MAT-MI forward problem was investigated using the finite element method (FEM). The corresponding FEM formulae describing the forward problem are introduced. In the finite element analysis, magnetic induction in an object with conductivity values close to biological tissues was first carried out. The stimulating magnetic field was simulated as that generated from a three-dimensional coil. The corresponding acoustic source and field were then simulated. Computer simulation studies were conducted using both concentric and eccentric spherical conductivity models with different geometric specifications. In addition, the grid size for finite element analysis was evaluated for the model calibration and evaluation of the corresponding acoustic field.

Comportamento da impedância elétrica dos tecidos biológicos durante estimulação elétrica transcutânea

OBJECTIVE: To analyze the electrical impedance of biological tissues during electrical stimulation in relation to different segments, surfaces and current frequencies, with increasing distance between electrodes. METHOD: 20 female volunteers of mean age 23 ± 2.25 years and mean body mass index 20.65 ± 1.44 kg/m2 were positioned in decubitus with one electrode placed proximally to the wrist and ankle joint lines, anteriorly and posteriorly, or on the posterosuperior iliac spine, and the other electrode was placed at distance of 10, 20, 30 and 40 cm, sequentially. Two currents (100 us and 10 mA) were applied: one at 100 Hz (LF) and the other at 2000 Hz modulated at 100% of the amplitude for 100 Hz (MF), with a minimum interval of seven days. The impedance was calculated indirectly using Ohm's Law, from the applied intensity and the electrical voltage picked up by a system consisting of a digital oscilloscope (TDS 210, Tektronix®) and a direct current generator (Dualpex 961, Quark®). For statistical analysis, Anova-F and Kruskal-Wallis were applied, with post hoc (SNK), Friedman test and Spearman correlation coefficient, taking p< 0.05. RESULTS: Despite similar electrical impedance behavior with increasing distance between electrodes for the two currents, there was a reduction in impedance under MF stimulation. In the limbs, approximately 50% of the impedance variance was explained by the increase in electrode separation, although this relationship was not observed on the posterior surface of the trunk. Independent of the current type, the trunk presented the lowest electrical impedance, followed by the lower limbs. CONCLUSION: The electrical impedance of the tissues was influenced by current frequency and the positioning and distance between electrodes, thus presenting a non-uniform pattern in the different segments.

Magnetoacoustic tomography with magnetic induction for imaging electrical impedance of biological tissue

An experimental feasibility study was conducted on Magnetoacoustic-Tomography with Magnetic Induction (MAT-MI). It is demonstrated that the 2-dimensional (2D) MAT-MI system can detect and image the boundaries between regions of different electrical conductivity with high spatial resolution. Utilizing a magnetic stimulation coil, MAT-MI evokes magnetically induced eddy current in an object which is placed in a static magnetic field. Because of the existence of Lorenz forces, the eddy current in turn causes acoustic vibrations, which are measured around the object in order to reconstruct the electrical impedance distribution of the object. The present experimental results from the saline and gel phantoms are promising and suggest the merits of MAT-MI in imaging electrical impedance of biological tissue with high spatial resolution.

A preliminary study on temperature changemonitoring using the MR current density imaging technique

Based on the fact that the electrical impedance of biological tissues is very sensitive to temperature, we have proposed a method to monitor local temperature changes inside the tissues. Using an analytic model and a finite element method model, we have analysed the effect of the local temperature change on the phase image obtained by the magnetic resonance current density imaging technique. We show preliminary experimental results of the temperature change monitoring performed with a 0.3 T magnetic resonance imaging system. We expect that the proposed method can be utilized for the development of non-invasive temperature imaging techniques.

Simulation of non-contact measurement of the electrical impedance using an anatomical model.

The measurement of the impedance of biological tissue can be a non-invasive method to find new data of diagnostic relevance. A system for a non-contact measurement of the electrical impedance of biological tissue is presented. The system consists of an excitation coil and two sensing coils, an upper and a lower coil. If the two sensing coils are coupled it can be used as a gradiometer coil. Numerical experiments with focus on the eddy currents in the tissue and on the detection of the small changes of the signal are carried out to calculate the fields, eddy current distributions and induced voltages. Hereby tests with different frequencies of the excitation current and different conductivities of a tissue block are used. Then the homogeneous tissue block is replaced with a fraction of the arm of an anatomical model which contains different tissue classes.

New approach to making instruments for measuring the electrical impedance of biological tissues

A new approach to the construction of instruments for measuring the electrical impedance of biological tissues is substantiated. The crux of the method is in the use of an electrical power generator for producing the electrical regime. Consideration is given to problems in the implementation of electrical power generators.

Principles of the impedance technique

A simplified treatment of the electrical impedance of biological tissues is presented, examining the sources of impedance changes and the requirements for recording these changes. The author covers small electrodes, simple models, resistivity of blood, the reactive component in bioimpedance, the use of bioadmittance, the use of the finite-element technique and impedance matching.

Transthoracic electrical impedance at 1 and 100 kHz--a means for separating thoracic fluid compartments?

The electrical impedance of biological tissues varies with their water and electrolyte contents. Alternating current above 5-10 kHz passes both intra- and extracellular fluid, and lower frequency current preferentially extracellular fluid. In an attempt to evaluate thoracic fluid in different compartments, transthoracic electrical impedance (TEI) was measured at 1 and 100 kHz in 15 consecutive patients, without overt left heart failure and under haemodynamic surveillance, during the first two days of myocardial infarction. To achieve different states of hydration the patients were given i.v. furosemide, either 40 mg t.i.d. (high dose group--HDG) or 20 mg once daily (low dose group--LDG). Effects of altered body position and the respective furosemide injections, were evaluated on both days. Mean 24-h-diuresis was 3.9 l in the HDG and 2.5 l in the LDG. After 24 h mean pulmonary arterial diastolic pressure had decreased by 30% in the HDG but remained almost unchanged in the LDG. By then mean basal TEI was increased only in the HDG, by 17% at 1 kHz and 13% at 100 kHz. On Day 1, within one hour after furosemide, TEI increased temporarily by 3-5%, at both frequencies and in both groups. On Day 2, this short-term increase was similar in the LDG at both frequencies and in the HDG at 100 kHz, but not at 1 kHz, consistent with a major extracellular fluid loss in the HDG. TEI at 1 and 100 kHz may thus reflect extracellular and total thoracic fluid, respectively.