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More than 34 000 new cases of breast cancer are registered annually in Russia with the patients age becoming significantly younger. 25% of women under thirty and 60% of those above forty are diagnosed as dyshormonal mammary glands (mastopathy) cases. Though mastopathy is not considered to be obligatory cancer prelude, breast cancer occurs 3 - 5 times more often in patients with diffuse dyshormonal noncancerous diseases of mammary glands and 30 - 40 times more often with nodular forms of mastopathy aggravated by proliferation of lactic gland epithelium [1]. This evidence has heightened the general interest in non-malignant growth opening the way to incidence reduction in breast cancer through effective curing of mastopathy. The existing methods of mastopathy diagnosis have certain applicability restrictions of both objective and subjective nature. The report presents main results of a comprehensive examination of 166 women (92 without breast pathology and 74 with mastopathy) with four methods: multifrequency electrical impedance mammography, ultrasonic investigation, x-ray mammography and puncture biopsy. [ABSTRACT FROM AUTHOR]

The aim of this pilot study was to investigate whether Extremely Low Frequency (ELF) Pulsed Electromagnetic Field (PEMF) exposure could alter Electroencephalographic (EEG), Electrocardiographic (ECG) and Skin Impedance (SI) human activity. Five subjects were recruited for a non-continuous and consecutive 5 days of testing. The 10 minute ELF PEMF 0-100Hz frequency included the ‘bundles' and delays, each lasting 20 msec. The skin impedance was recorded by applying the signal frequency sweep from 1Hz to 1MHz, using ‘whole-body' Multiple Frequency Bioelectric Impedance Analysis (MF-BIA). The EEG activity was recorded from 16 channels, together with ECG using independent data acquisition system. The skin impedance, EEG and ECG data was analysed for 5-day exposure/control and before/after conditions. The results of this pilot study can be used for optimisation of ELF PEMF exposure time-window effect on the human body as well as to understand the underlying mechanisms of it's interaction with human biological system. [ABSTRACT FROM AUTHOR]

The aim of this work is to describe the ongoing development of a non-invasive continuous glucose monitoring system based on Impedance Spectroscopy (IS). Previous work has shown the importance of taking a multi-sensor approach to aid in the compensation of various potentially perturbing parameters, such as the impact of environmental/body temperature, changes in the blood perfusion of the measured skin, underlying tissue volume and changes in the sensor / skin contact due to movements. Here we describe how this multisensor concept has been implemented into an integrated functional model (FM). In our recent studies, this integrated FM has been tested in an experimental clinical study in subject groups with patients with Diabetes type I/II (D) and healthy subjects (ND). The relation between changes in the blood glucose concentration and the impedance of the skin / underlying tissue has been investigated under controlled clinical conditions. The clinical study protocol allowed the use of an intravenous glucose clamp technique to control the subject's glucose concentration and enabled two hyperglycemic episodes to be achieved within a ten hour study day. [ABSTRACT FROM AUTHOR]

Several studies have shown that the amplitude of the Impedance CardioGraphy (ICG) signal can not simply be linked to cardiac stroke volumes. The time relationships of the ICG-signal, however, may provide vital clinical information, especially when the ICG is compared to the waves in the Electro- CardioGram (ECG). The time difference between the two signals reflects the time difference between the electrical and mechanical activity of the heart, which is controlled by the autonomic nervous system. The autonomic system is affected in several diseases, e.g. diabetes mellitus and Parkinson's disease (PD). Earlier studies have shown that a specific time interval, the Pre-Ejection Period (PEP), is related to sympathetic activation. The PEP, however, is based upon marker points that are often difficult to trace. The present study introduces a novel time interval, the Initial Systolic Time Interval (ISTI), defined as the time difference between the R-point in the ECG and the C-point in the ICG. The relationship between PEP and ISTI was investigated in three groups of subjects. The clinical significance of ISTI was investigated in two groups of PD patients and healthy controls. [ABSTRACT FROM AUTHOR]

We describe the results of anthropological study of healtly Russian children which included both anthropometry and bioimpedance analysis of body composition (n=946). The whole-body impedance was measured according to a conventional tetrapolar scherme using BIA analyzer ABC-01 "Medass" (SRC Medass, Russia). We report a normal ranges for phase angle and BIA body composition parameters, such as absolute and relative contents of fat (FM, %FM) and fat-free mass (FFM) for boys and girls depending on age. FFM was assessed using Houtkooper equation. The obtained estimate of body composition were compared with those derived from skinfold anthropometry using Slaughter, Deurenberg, Matiegka, and other equation. Also, the results of correlation and factor analysis of phase angle and BIA body composition with various anthropometric indexes are discussed. [ABSTRACT FROM AUTHOR]

With the worldwide epidemic growth of obesity prevalence, nutritional assessment has become of paramount importance, both clinically and epidemiologically. Bioelectrical Impedance Analysis (BIA) is an alternative for the calculation of % Body Fat (%BF), but, so far, it requires population specific predictive formulae [1]. Until these are developed for the Colombian population, we wanted to know which of the published formulae could be best used in our region. Six of them were selected to calculate %BF from BIA measurements taken at 50 kHz with a Xitron 4000B Bio-Impedance Analyzer and the results compared against %BF calculated from skin fold (SF) measurements with a Skyndex I calliper, according to Durnin and Womersley [2]. Subjects were 68 healthy young male volunteers (average age: 20.03 y, range 18.04 - 24.85 y), recruited among students at the University of Caldas- Manizales-Colombia. The Bland and Altman method [3] was used to determine the agreement between BIA and SF for the calculation of %BF. Best results were obtained with the van Loan and Mayclin [4] formula (mean difference -0.84, percentage points with 95% confidence interval -5.91 and 4.24), but they suggest the necessity of developing our own predictive formulae if we are to use BIA and SF interchangeably. [ABSTRACT FROM AUTHOR]

In bioimpedance analysis (BIA), total body water volumes (TBW) are generally estimated from empirical correlations of the subject weight and his impedance index (H2/R50) where H denotes the subject height and R50 is his wrist-ankle resistance at 50 kHz. We have proposed recently [4] a modification of bioimpedance spectroscopy (BIS) for measuring directly TBW (Vtnm) from R∞, the wrist-ankle resistance extrapolated at infinite frequency and a mean TBW resistivity ρ∞ inferred from dual energy X-ray absorptiometry (DXA) measurements in 58 healthy subjects, using Hanai's theory to account for non conducting elements. In this paper we investigate whether our new method could also be applied to single frequency bioimpedance at 50 kHz by using an appropriate 50 kHz resistivity. We have compared TBW volumes (Vt50) given by this method with our modified BIS method with BIA correlations from the literature and the classical BIS method using TBW deducted from fat-free mass measured by DXA (Vtd) assuming a hydration rate of 73.2% as reference. A validation of our methods was made using a 2nd set of data for 21 subjects not used for the determination of resistivities. [ABSTRACT FROM AUTHOR]

Bioimpedance spectroscopy (BIS) has proved useful for the rapid accurate and quantification of lymphoedema. The underlying principle is that the impedance of a limb to an applied low frequency alternating electric current is inversely proportional to the quantity of extracellular fluid, including lymph. While many studies have shown a high degree of concordance between impedance and limb volume measurements, the question has often been asked: "How is this influenced by the form of lymphoedema?" Lymphoedema may present in various forms, e.g. primarily fluid, fibrotic etc. Broadly, these may be envisaged to represent a continuum from "purely" fluid through gel-like to a pseudo-membraneous tissue-like structure. BIS allows estima-tion of tissue capacitance which for biological structures is a characteristic of the cell membrane and tissue inter-faces. This study tested the hypothesis that membrane capacitance (Cm) would differentiate limbs with lym-phoedema from normal. Cm was measured (SFB3, Im-pediMed Ltd, Brisbane) for both arms of 116 women with no history of lymphoedema and 41 women with clinically affirmed unilateral post-mastectomy lymphoe-dema. [ABSTRACT FROM AUTHOR]

Tetrapolar, whole-body (hand-foot) bioelectrical impedance (Zwb) is utilized in body composition analysis for direct assessment of soft tissue hydration (Vector BIA) and indirect assessment of lean and fat soft tissue mass (BIA prediction equations). Limbs and trunk contribute to Zwb by 90% and 10%, respectively. We determined the effect on Zwb of local edema localized in one leg. Resistance (R) and reactance (Xc) components of Z vector was measured at 50 kHz (BIA-101, RJL Systems-Akern, Italy) in 20 adult male patients without edema, before and three days after a surgical procedure on vessels of one leg (femoro-popliteal bypass) that induced pitting edema in that leg. Zwb were measured from hand and foot of the right and left side. Z from the leg (Zleg) was measured from the pair of electrodes on foot and the other pair on the trochanter. Data were analyzed with Vector BIA (Piccoli's RXc graph method, 95% confidence ellipses) that considers Zwb and Zleg as bivariate gaussian random vectors (expressed in Ohm/meter of conductor). Baseline mean vector from legs of either side, Zleg was significantly shorter than Zwb on the R-Xc plane (separate 95% confidence ellipses). [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate and compare segmental bioimpedance spectroscopy (SBIS) measurements of arm volume and muscle to 40K and MRI measurements. 31 hemodialysis (HD) patients (17 male and 14 female, weight, 55.7±4.5 kg, BMI 27.6±5.5 m3/kg) were studied pre HD. MRI and partial body 40K of the arm (PBKArm) were measured. Arm bioimpedance was measured with the Hydra bioimpedance spectroscopic device (Xitron 4200). The length of the arm from wrist to ipsilateral shoulder was measured with soft tape. Arm extracellular (Re) and intracellular resistance (Ri) were obtained from a program based on Cole-Cole model provided by Xitron. Extracellular (ECVa) and Intracellular volumes (ICVa) in the arm were calculated. Arm fluid volume using SBIS was defined as VArm =ECVa+ ICVa. The correlation of the VArm and arm skeletal muscle (MSMRI) was R2=0.65 (MSMRI =0.89*Varm+0.15), that between PBKArm to VArm (R2 =0.53, VArm =2.34*PBKArm + 2.1) and to MSMRI (R2=0.36, MSMRI=2.4* PBKArm + 7.6), respectively. This study shows that arm SBIS measurement provides an easy, portable, low-cost technique for estimation of muscle mass in the arm, which can be performed frequently. [ABSTRACT FROM AUTHOR]

Malnutrition is frequent in end-stage renal disease patients treated by dialysis. Few data are available on the evaluation of nutritional status in chronic kidney disease (CKD) patients at different renal functional stage. The aim of this study was to evaluate the effect of the decreased renal function on body composition of CKD patients. To assess renal function, glomerular filtration rate (GFR) was measured as the renal clearance of 99mTc-DTPA in 1016 (533 males and 483 females) CKD patients. Body composition was evaluated by means of single-frequency bioimpedance analysis (BIA). Values of fat mass (FM), fat-free mass (FFM), body cell mass (BCM) and extra-cellular water (ECW) were indexed to squared height of patients, similarly to body mass index (BMI). BMI and FMI significantly increased with the reduction of GFR in females, while were unchanged in males. FFMI was unmodified independently from the gender. BCMI significantly decreased only in males, while was unmodified in females. Finally, ECWI significantly increased in all patients. These results indicate significant differences between male and female CKD patients, and in particular a different effect of decreased GFR on body mass and body composition in male and female patients. [ABSTRACT FROM AUTHOR]

Hyper-hydration, malnutrition, and arterial hypertension are the most common risk factors associated with mortality in peritoneal dialysis PD patients. Segmental bioimpedance measured placing electrodes at the ends of the superior and inferior limbs, and in the trunk can be used to monitor changes in regional fluid status. In this work three impedance based estimators were analyzed: impedance Z, impedance divided by the height of the patient Z/H, and impedance multiplied by the body mass index ZBMI. We measured 6 configurations of segmental impedance measurements, at 50 kHz, in 23 male patients undergoing PD, classified as normo-hydrated or hyper-hydrated. Wilcoxon test was used to analyze the bioimpedance change produced by a PD session. Mann-Whitney U test was used to analyze the separation between groups obtained by means of clinical parameters. Spearman correlation was used to study the correlation between segmental impedance and clinical assessment. Statistical significance was set at P < 0.05. The ZBMI index gives information about the specific resistivity of tissues and not to fluid and fat mass changes. [ABSTRACT FROM AUTHOR]

We have developed a technique to monitor dry weight (DWM) using a segmental bioimpedance technique to continuously measure the change in resistance and resistivity (ρ) in the calf during hemodialysis (HD).The DWM was designed based on multifrequency bioimpedance spectroscopy (BIS) with frequencies from 1 to 300 kHz. An algorithm combines two parameters to determine DW, flattening of the curve of change in extracellular resistance (ΔRE0/REt<0.01) and normalized resistivity (μ = ρ /body mass index). 31 patients (12f/19m) were studied. Systolic blood pressure (SBP) and blood volume (BV) were measured. After three baseline (BL) measurements, post HD weight was gradually reduced every treatment. 21 patients reached DW criteria but 10 were still overhydrated (OH) due to lack of compliance. A significant decrease in post HD weight and increase in μ were observed in BL compared to DW (Wt 75.3±15 vs. 74.1±15 kg, p<0.001; μ 18.6±2.5 vs. 20.4±2, p<0.001) in OH (Wt 82.3±38 vs. 80.1±36 kg, p<0.05; μ 14.6±1.9 vs. 16.3±1.4, p<0.05). In patients at DW, the curves of ΔRE0/REt were flat and the μ was closer to normal range, while in OH patients neither the flattening curve nor normal μ were observed. [ABSTRACT FROM AUTHOR]

Segmental body composition measurements in the limbs and the trunk may be important to monitor obese patients or athletes during their training. By measuring sequentially the resistances of 5 current lines connecting the hands and feet, it is possible to calculate, by solving a system of 5 equations, the resistances of each limb and the trunk. We present a method for measuring the fat-free-mass (FFM) and the fat tissue mass (FM) of the limbs based on comparison with segmental DXA data. The impedance meter used in this study was a prototype with 4 plantar electrodes and 4 electrodes for the hands derived from an existing foot-to-foot impedance meter which provides a high frequency resistance. Impedance and DXA measurements were taken simultaneously on 170 healthy subjects to obtain equations relating FFM of the limbs to their resistances, the patient weight and his height. For the limbs FM, correlations of the body FM, age and BMI were used. Then, for validation these equations were tested on a 2nd group of 87 subjects who underwent the same impedance and DXA protocol. Comparisons of FFM by impedance and DXA for the validation group show that FFM values from impedance were not significantly different from those from DXA. [ABSTRACT FROM AUTHOR]

In maintenance hemodialysis patients (MHD) analysis of body composition is a key point to assess nutritional status. Dual-energy X-ray absorptiometry (DXA) is a reference method for a detailed assessment of fat mass (FM) and lean body mass (LBM). The reliability of single-frequency bioelectrical impedance (sf-BIA) versus multi-frequency (mf- BIA) to analyze body composition in MHD is debated. Aim: to evaluate the adequacy of sf-BIA and mf-BIA, in comparison with DXA, to evaluate LBM in MHD patients. Patients (9 f, 18 m), 32-88 yrs, BW 42-94 kg, BMI 17.5-34.4 kg/m2, on MHD since 0.5-17.4 years. LBM was measured, in the interdialytic period, with DXA and BIA,with 2 sf-BIA and with 1 mf-BIA analyzer. A very close correlation was found between LBMBIA and LBM-DXA (R 0.901 - 0.921). Mean values of LBM were very similar with the different techniques. LBM was 45.1.1±8.8 kg (DXA); 45.1±8.5 (sf1-BIA); 45.8±8.8 (sf2-BIA); 44.4±11.5 (mf-BIA). Prediction errors were 3.4 kg for sf1-BIA, 4.0 kg for sf2-BIA, and 5.0 kg for mf-BIA. In conclusion, BIA is a reliable method to evaluate lean body mass in MHD. [ABSTRACT FROM AUTHOR]

Haemodialysis has been considered an effective therapy for patients with end-state renal disease; however patients can suffer from adverse side effects during haemodialysis, which are related to the excess shift of fluids between the extracellular and intracellular spaces, as shown in several publications. In this work we used a multifrequency bioimpedance sensor that allows us to determine the fluid volumes and their variations during haemodialysis. Clinical measurements were done with 10 patients (7F, 3M) during 60 HD sessions. Impedance data were recorded on local tissues and for each patient; three impedance sensors were attached to the arm, abdomen, and leg. Bioimpedance data, arterial blood pressure, blood volume and blood haematocrit variations were recorded continuously during the HD sessions. Estimators for the ECW, ICW and TTW volumes and ratios were developed and monitored during the HD sessions. ECW and TTW volumes and the ratios ECW/TTV ECW/TTW showed a clear decrease in response to ultrafiltration. However the behaviour of ICW volume variation was not the same in all patients. The ratios ICW/TTV and ICW/TTW showed an increase between the pre and post-HD states, which indicate that water is removed more from the extracellular space. [ABSTRACT FROM AUTHOR]

The aim was to develop a fluid estimator for haemodialysis with the potential to indicate hypotensive disorders so that counter measures can be taken in time. The bioimpedance was measured longitufinally on the lower leg with a four-electrode arrangement at six frequencies ranging from 10 kHz to 500kHz. The estimator proposed considers the anisotropy of music tissue and is based on a cylindrical model with homogeneously distributed extra- and intra-celluar compartments. The dependence of the cell constants on the circumference was determined with anisotropic FE models in which the conductivities were simulated with Cole-Cole models. Data was gathered from 25 persons during 108 haemodialysis sessions. It was fitted to a Cole-Cole model with parameters Z0 and Z∞, the lumped tissue impedance at low and high frequencies. From these parameters the extra-celluar volume fraction was estimated with the help of the cell constants from the FE simulations. Results of the data analysis and a proposal for a new predictor for a circulatory are presented. [ABSTRACT FROM AUTHOR]

Bioimpedance data are mostly used to quantify the size (body composition, fluid volumes) and sometimes the anatomical location of tissue masses. Such measurements are usually confined to cases where pool sizes are static or slowly changing. These measurements are useful in monitoring patient progress in a variety of evolving clinical situations. Dynamic quantification of rapidly changing whole-body pool sizes is more demanding but is also needed. It has been achieved, especially during and surrounding dialysis therapy. Such measurements promise improved answers to the difficult question of how much water to remove during dialysis sessions. Anatomically specific dynamic quantification is a further step that appears capable of identifying sub-pools whose changes in size may predict and explain different predispositions to hypotension during the course of dialysis. The correlation of anatomically specific measurements of many kinds with bioimpedance is being used to validate information on pool dynamics when the pools cannot be precisely imaged and tracked. We present here bioimpedance data taken simultaneously on the leg, arm, and trunk of a group of 30 dialysis patients, 8 of whom were predisposed to hypotension, and 5 of whom had unusually high rates of water removal. These data can identify encumbered movement of water from the interstitial components of skeletal muscle to those of the trunk and are useful in predicting anatomical or situational predispositions to hypotension. [ABSTRACT FROM AUTHOR]

This paper describes a system that enables quantitative monitoring and evaluation of the influence of a pulse magnetic field on a living organism with the use of bioimpedance measurement. We use the bio-impedance method to evaluate the haemodynamics. The magnetotherapeutic instrument uses a couple of Helmholtz coils as the applicator. The magnetic field strength is approximately 60 mT. The current of these coils is controlled by a pseudo-random impulse signal. The bio-impedance is measured by the four-electrode method, using an RF narrow band vector bio-impedance meter on the forearm. During exposure to the magnetic field the bioimpedance signal level increases above the normal and the maximum level is reached after about 10 minutes. The maximum value is approximately 50 % higher than the normal level. [ABSTRACT FROM AUTHOR]

Electrodermal activity (EDA) is well known for sensing emotional activity and autonomous nerve activity. The changes are easily detected by means of electrical measurements, and since the sweat ducts are predominantly resistive, a low-frequency conductance measurement is appropriate for measurement of exogenous EDA. The endogenous measurements are carried out as dc potential measurements. The main purpose of this study was to compare the endogenous and exogenous responses in order to acquire a better understanding of the underlying mechanisms. Measurements of exogenous and endogenous EDR were conducted simultaneously in the palms of healthy volunteers, using the same electrodes for both measurements. The results suggest a high degree of correlation between skin impedance and skin potential, even if a bi-phasic skin potential response (SPR) wave occurred for some people. A possible interpretation of these results, is that the endogenous EDR activity is produced by streaming potentials in the sweat ducts. The exogenous pulse, on the other hand, will be due to the shunting effect of the filled sweat ducts, and the conductance will not completely return to baseline until these ducts are drained. [ABSTRACT FROM AUTHOR]

Magnetic induction plethysmogram comprises the time course of electromagnetic power absorbed in a patient's body on the induction of eddy currents there. Time variation of the plethysmogram is caused by physiological processes in the body region close to the transducer's inductor coil: displacement of organs, variation of their shape, volume redistribution processes of body liquids. Depending on the location of the transducer, the signal waveforms have different shapes and magnitudes. This report gives an overview of a study of the variation of the magnetic induction plethysmogram and Foucault cardiogram (i.e. a variant, if the transducer is positioned in the heart region) waveform and magnitude on a supine human thoracic front surface. [ABSTRACT FROM AUTHOR]

The frequency range of Electrical Impedance Myography has been extended to 2 MHz, revealing strong increases in reactance starting in the neighbourhood of 3-500 kHz, details depending on muscle and subject. "Reduced variable" Nyquist plots are presented for different segments of the muscle, to demonstrate the unity of the high frequency behaviour with that below 100 kHz. Kramers-Kronig analysis demonstrates compatibility of the rise in X with continued fall in resistance with increasing frequency, and evidence against the "transmission line" hypothesis is presented. [ABSTRACT FROM AUTHOR]

The laboratory model of the pulse-wave parameter recorder (PWPR) for diagnostics of the organism functional state (FSO) by the change of bioimpedance (complex resistance of vital tissue) has been proposed. The novelty of the approach is that bioimpedance is incorporated in the circuit of positive feedback of active oscillator. Nonlinear component of bioimpedance significantly influences on the oscillation frequency of associated system. The bioimpedance changes with the change of FSO. At that, changing of the spectrum envelope shape and frequency bias of system oscillations took place. Thus, frequency characteristic of system allow find the quantitative measure for defining of FSO. Converting of the bioimpedance change into frequency variation and computer processing of frequency-modulated signal permit to create a device which has operation speed and sensitivity are sufficient to record ultra-small changes of conduction that characterize the change of the functional state of the organism during its vital functions. [ABSTRACT FROM AUTHOR]

In the usual technique for gastric motility assessment, electrical potential variation of gastric mioelectrical activity is recorded. Electrical bio-impedance (EBI) is useful mainly for gastric emptying studies using long time recordings. In this study we evaluated the gastric motility of 11 subjects being in fasting and postprandial conditions. Experiments using drugs to increase the gastric motility and to change the gastric acidity were performed in three of these subjects. With Fourier analysis of short time recordings made during different steps of the experiments (using four electrodes) we found the dominant peaks at frequencies around 2-3 cpm. These peaks had relative variations in heights and widths. Also the intensity of the gastric EBI spectra at higher frequencies increases in the postprandial state and after the use of drugs to increase the gastric motility. These results were similar than those reported using epigastrography. In this study short time bioelectrical impedance assessment for the evaluation of gastric motility is proposed. [ABSTRACT FROM AUTHOR]

Using a proprietary local bioimpedance analyzer that applied current at a frequency of 10 kHz we studied the changes in the absolute value and the phase angle of the arm's impedance when we applied a pressure with a pressure cuff located in the arm of 22 voluntaries (11 men and 11 women) aged between 21 and 44 years old. A direct proportionality between variations in the blood volume after the application of the pressure pulse was expected, according to the literature. Combining the observed changes in impedance with the mechanical compliance of the blood vessels, a relationship between pressure changes, impedance changes and haematocrit can be established. We also studied the changes in the impedance when a force was produced by the hand. The force strength was measured with a load cell. We observed a direct proportionality between the absolute value of the admittance and the applied pressure in the cuff, within a certain range, as expected. However, we noticed a temporal delay in the response of the admittance module variation with respect to the increase in the pressure of the cuff. The mean value of the admittance module measured without the application of pressure was 15.4 mS ± 1.6 mS (mean ± S.D.) for men and 11.7 mS ± 1.9 mS for women. [ABSTRACT FROM AUTHOR]

In the endodontic treatment of the root canal, one of the most important procedures is the root canal length determination. Apex-locators are commercial electronic devices used to determine canal length by measuring the electrical impedance. The verification of such instruments in-vivo is hard to perform because the only accurate way of measurement is by extracting the tooth and then measuring the canal length. For this reason, testing of apex-locators and their comparison as well as new measuring method evaluation are often performed by model-based in-vitro measurements on extracted teeth. In this paper we demonstrate that significant differences between electrical properties of the model and the vital tooth exist. Frequently used physical models in current studies consist of a tooth immersed either in saline solution or in freshly mixed alginate. In order to investigate the electrical properties of these physical models, we have measured the value of root canal impedance Z and the elements of two-element parallel equivalent circuit (Rp, Cp) in both physical models and compared the results with in-vivo root canal impedance measurements. We have shown that the results of the measurements of electrical impedance on the physical models significantly differ from in-vivo measurements. [ABSTRACT FROM AUTHOR]

A feasibility of bioimpedance measurement for the evaluation of skeletal muscle contractile state was examined. The 4-electrode impedance spectra of relaxed, moderately contracted and geometrically changed muscle biceps brachii were compared in a human subject over the frequency range from 300 Hz to 75 kHz. The frequency response was parameterized and a simple neural network was used to determine contractile state of a muscle. The parameters that could indicate skeletal muscle contractile state were found to be a frequency of the phase angle minimum and the rate of phase angle change with the frequency. The impedance spectra data set was further examined by a principal component analysis. The score plots show a data grouping of geometrically changed, relaxed and contracted muscle. [ABSTRACT FROM AUTHOR]

Efficiency of bioimpedance measurements were assessed and used to evaluate the passage of urine, as well as motility and structure of the upper and lower urinary tracts. The rheographs "RPKA2-01", "ITU-6", and bioimpedance analyzer "ABC-01" produced by Medass (Russia) were used with a probe equipped with 9 individual electrodes. During measurements the probe was introduced endoscopically into various regions of urinary tract in patients with the urologic diseases. Three diagnostic approaches were assessed: 1. The multichannel impedance ureterography (MIUG) was developed to quantitatively and qualitatively estimate the ureteral peristalsis. 2. The impedance ureteromety yielding impedance ratio (Zlow/Zhigh) detected the region of ureteral stricture if this ratio surpassed the critical level. 3. The urethral wide-band impedance measurements made at the frequency range 5-500 kHz revealed the intrinsic individual peculiarities of male and female urethra that could be helpful in diagnostics of urination disorders. The examined bioimpedance methods could serve as efficient diagnostic tools characterized by portable equipment, pick-and-go application, lack of radiation, and the reliable quantitative output. [ABSTRACT FROM AUTHOR]

Accurate root canal length determination is crucial for successful endodontic procedure where the root canal of the tooth is opened, cleaned and sealed. Impedance method is becoming a standard method for determination of the position of apical foramen. Current devices rely on determination of apical foramen from the ratio of impedances measured at two or more frequencies. The investigation is aimed in determination of optimal parameters for determination of apical foramen with best possible accuracy. The investigation has revealed an optimal ratio of 0.79 determined at frequencies 1 kHz and 500 Hz with a standard deviation of about 1 mm. [ABSTRACT FROM AUTHOR]

We analyzed more than 2000 electroimpedance images of the mammary gland in norm and with pathology. The research was carried out utilizing the electrical impedance computer tomograph «MEIK»® (current 0.5 mA, frequency 50 kHz). The following particularities of the electrical impedance image were established. In the norm the electrical impedance image reflected a regular anatomic structure of a mammary gland and the index of the mean electrical conductivity corresponded to the age norm. In case of pathology either changes of the anatomic structure of a mammary gland or changes of its mean electrical conductivity index were observed. Thus, estimation of the electroimpedance image should include both a visual analysis of the image as well as quantitative. The visual estimation of the electroimpedance image includes analysis of the following details: the mammary gland contour (presence of deformations, infiltration); the mammary gland anatomy (changes of anatomy, displacement of internal structures, perifocal infiltration); the lacteal sinus zone (visualization, dilatation); local changes of electrical conductivity (presence of hypo- or hyperimpedance areas). [ABSTRACT FROM AUTHOR]

Cerebral blood flow autoregulation (CBF AR) is the phenomenon that makes blood flow constant within a physiological range regardless of blood pressure variations. When systemic arterial pressure (SAP) increases, vasoconstriction is taking place in the brain. The objective of the present study was to compare SAP, rheoencephalogram (REG), and carotid flow (CF) measured by Doppler ultrasound. Twentyeight anesthetized Yorkshire pigs were measured to evaluate CBF AR during several CBF manipulations: haemorrhage, positive end-expiratory pressure (PEEP), and transitory SAP decrease and increase. Data were sampled with 200 Hz and processed off-line. 1) Haemorrhage elicited a decrease in SAP and transitory increases in REG and CF amplitude; 2) PEEP resulted in a decrease in SAP and increases in REG and CF amplitude; 3) PEEP after haemorrhage caused decreases in SAP, REG and CF amplitudes. When CBF AR was present, it was detected by both REG and carotid flow. Following haemorrhage, CBF AR was lost; CF and REG passively followed SAP. The clinical importance of these findings is that REG can be measured more conveniently and continuously in humans than can Doppler ultrasound. Therefore, measurement of CBF autoregulation by REG has potential for use as a life sign monitoring modality. [ABSTRACT FROM AUTHOR]