Tadamitsu Iritani

Measurement of the Electrical Bio-Impedance of Breast Tumors

A new impedance analytical system was developed, and measurements were performed over a frequency range of 0-200 kHz by the three-electrode method. The three electrodes consist of a coaxial needle electrode inserted into the tumor and a large reference electrode on the upper abdominal wall. The electrical bio-impedance was measured in 54 patients with breast tumors. The biological tissue can be regarded electrically as an equivalent consisting of extracellular resistance (Re), intracellular resistance (Ri), and electrical capacitance of the cell membrane (Cm). These three parameters were calculated from the measured values of electrical bio-impedance by the curve-fitting technique using a computer program. It was found that Re and Ri of breast cancers were significantly higher than those of benign tumors (p less than 0.01), and that Cm of breast cancers was significantly lower than that of benign tumors (p less than 0.01). Measurement of the electrical bio-impedance of breast tumors may have value in the differential diagnosis of breast lesions.

Fastin vivo measurements of local tissue impedances using needle electrodes

The objective of the research is to show an in vivo, fast method of measurement of local tissue bio-impedance in the beta dispersion region (0–200 kHz). A needle electrode is used for the purpose. The performances with respect to circuits, electrodes, measurement area and electrical representations are evaluated. A measurement example is shown, and the electrical representations are discussed and compared using it. The method discussed, although invasive, is considered to be useful for local tissue diagnoses concerning structures and physiological functions.

Electrical properties of extracted rat liver tissue

We attempted to investigate the process of ischemia-induced disturbances in the rat liver, employing the electrical bio-impedance technique. The electrical bio-impedance was measured continuously over 6h by the 4-electrode method, at various incubation temperatures, in six liver samples extracted from male Wistar rats. The electrical properties of biological tissues can be expressed in terms of three parameters: extracellular resistance (Re), intracellular resistance (Ri) and cell membrane capacitance (Cm). These three parameters were calculated from the measured values of the electrical impedance by the curve-fitting technique, using a computer program. The Re value increased rapidly after the rat livers were extracted, and then decreased slowly. The Revalue reached a peak after about 13 min at 36°C, and then decreased slowly, becoming constant after 3h. There was a negative correlation between the Tmax of Re (the time when Re reached a maximum) and the incubation temperature (R=−0.973,P<0.001). The Ri value decreased once in the early stage after extraction, followed by almost no change and then an increase after 4h at 36°C. The Cm showed a similar pattern of change to the Re value, and a negative correlation was also found between the Tmax of Cm and the incubation temperature (R=−0.969,P<0.001). The increases in the Re and Cm values, and the decrease in the Ri value for quite long periods after the blood flow has stopped, suggest an increase in the resistance of extracellular fluid due to a decrease in its volume, an increase in cell membrane capacitance due to cell swelling, and a decrease in cellular fluid resistance due to an increase in its volume. The time when the Cm value decreases rapidly after an initial gradual decrease after the peak corresponds well with the time when the Ri value begins to increase, from which it is estimated that cell lysis proceeds and that the flow of extracellular fluid into the cell begins at this time. The findings of this study suggest the possibility of estimating the changes in liver tissue or the tissue structure due to ischemia.

Standing Wave Radar Capable of Measuring Distances down to Zero Meters

Various types of radars have been developed and used until now-such as Pulse, FM-CW. and Spread Spectrum. Additionally, we have proposed another type of radar which measures distances by using standing wave. We have named it as Standing Wave Radar. It has a shorter minimum detectable range and higher accuracy compared to other types. However, the radar can not measure distances down to zero meters like other types of radars. Minimum detectable range of the standing wave radar depends on a usable frequency range. A wider frequency range is required if we need to measure shorter distances. Consequently, we propose a new method for measuring distances down to zero meters without expanding the frequency range. We use an analytic signal, which is a complex sinusoidal signal. The signal is obtained by observing the standing wave with multiple detectors. We calculate distances by Fourier transform of the analytic signal. Moreover, we verify the validity of our method by simulations based on numerical calculation. The results show that it is possible to measure distances down to zero meters. In our method, measurement errors are caused by deviations of position and gain of the detectors. They are around 10cm at the largest if the gain deviations are up to ±1% and the position deviations are up to ±6% of the spacing between the detectors. Prevalent radars still have a common defect that they can not measure distances from zero to several meters. We expect that the defect will be eliminated by putting our method into practical use.

A new method for noninvasive measurement of multilayer tissue conductivity and structure using divided electrodes

This paper outlines a new method for measuring multilayer tissue conductivity and structure by using divided electrodes, in which current electrodes are divided into several parts. Our purpose is to estimate the multilayer tissue structure and the conductivity distribution in a cross section of the local tissue by using bioresistance data measured noninvasively. The effect of the new method is assessed by computer simulations using a typical two-dimensional (2-D) model. In this paper, the conductivity distribution in the model is analyzed based on a finite difference method (FDM) and a steepest descent method (SDM). Simulation results show that the conductivity values of skin, fat, and muscle layers can be estimated with an error of less than 0.1%. When random noise at various levels is added to the measured resistance values, estimates of the conductivity values for skin, fat, and muscle layers are still reasonably precise: their root mean square errors are about 1.06%, 1.39%, and 1.61% for 10% noise. In a 2-D model, increasing the number of divided electrodes permits simultaneous estimates of tissue structure and conductivity distribution. Optimal configuration for divided electrodes is examined in terms of dividing pattern.

Changes in carotid blood flow and electrocardiogram in humans during and after walking on a treadmill

Blood flow velocity in the common carotid artery and the electrocardiogram were measured simultaneously by telemetry in seven male subjects during 20-min walking on a treadmill at an exercise intensity corresponding to a mean oxygen uptake of 26.0 (SD 2.9) ml · kg −1 · min −1. The mean cardiac cycle was shortened from 0.814 (SD 0.103) s to 0.452 (SD 0.054) s during this exercise. Of this shortening, 73% was due to shortening of the diastolic period and 27% to shortening of the systolic period. In the relatively small shortening of the mean systolic period [from 0.377 (SD 0.043) s to 0.268 (SD 0.029) s], the isovolumetric contraction time was shortened by 56%. During exercise, the heart rate (fc) increased by 79.4% [from 74.3 (SD 9.3) beats · min −1 to 133.3 (SD 14.8) beats · min −1], and the peak blood velocity (S1) in the common carotid artery increased by 56.1% [from 0.82 (SD 0.10) m · s−1 to 1.28 (SD 0.11) m · s−1]. After exercise, the S1 decreased rapidly to the resting level. The fc decreased more slowly, still being higher than the initial resting level 5 min after exercise. The diastolic velocity wave and the end-diastolic foot decreased during exercise. The blood flow rate in the carotid artery increased transiently by 13.5% at the beginning of exercise [from 5.62 (SD 0.63) ml · s−1 to 6.38 (SD 0.85) ml · s−1] and by 26.5% at the end of the exercise period [from 5.62 (SD 0.63) ml · s−1 to 7.11 (SD 1.34) ml · s−1]. The increase of blood flow in the carotid artery at the onset of exercise may have been mainly related to cerebral activation, and partly to an increase of blood flow to the skin of the head. The physiological significance for cerebral function of the increase of blood flow in the artery after the end of exercise is unknown.

Measurement of distance and velocity of a moving target by short-range high-resolution radar utilizing standing wave

In this paper, we propose a radar using standing wave, and describe the measurement principle and experiment results. This radar does not use a time delay like usual radars but uses the amplitude of the standing wave. As a result of experiments, this radar could measure the distance and velocity of a moving target using bandwidth of only 76 MHz permitted by the specification of low-power radio equipment to detect moving objects (24 GHz band). The bandwidth of the radar is narrower than that of a millimeter wave radar.

Estimation of bioimpedance distribution in the local tissue using divided electrodes

Electrical impedance tomography (EIT) is 2-D or 3-D image of electrical impedance distribution in a living tissue. It has become expected as a different method to obtain a tissue characteristic for various medical diagnoses. To realize a practical EIT measurement system, it is an important subject to choose a proper configuration of the electrodes, because the EIT is estimated from impedance data, which is non-invasively measured by electrodes. In this study, a new configuration of the electrodes, called divided electrode, is proposed for a short time measurement of bio-impedance in a cross section of a local tissue. Its capability is examined by computer simulations, where a distributed equivalent circuit is used as a model in the cross section of the tissue. Estimation of impedance parameters is carried out by use of the Newton Method. As results of them, usefulness of the proposed method is confirmed by computer simulations using a typical layered tissue model.

Impedance measurement of tumors and its application to diagnoses

An in vivo impedance measurement system using a coaxial needle was developed to investigate the usefulness of impedance information for tumor diagnoses. Impedance in the range of 0 to 200 kHz was measured, and an equivalent circuit representing the tissue structure of tumors was derived. Malignant breast and lung tumors had significantly higher impedances than benign tumors, indicating the system could be useful for tumor diagnoses.<<ETX>>

Estimation of multilayer tissue conductivities and structures using divided electrodes

To estimate inner multi-layer tissue structures and conductivities distribution in a cross section of the local tissue by using bioresistance data measured noninvasively, a new measurement method using divided electrodes is provided, in which current electrodes are divided into several parts. Our purpose is to assess the effects of the new method by computer simulations using a typical two-dimension (2D) model. Conductivity distributions and structure of the simplified (2D) model are analyzed based on a combination of a finite difference method (FDM) and a steepest descent method (SDM). Simulation results demonstrate that conductivity values of multi-layer tissue (skin, fat, muscle) can be estimated with an error less than 0.1%. Different strength random noise is added to measure resistance values, estimations of conductivity values for skin, fat and muscle are still reasonable precise. Optimal configuration for such divided electrodes is examined in terms of dividing pattern.