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Biomedical subjects

J Ikebe

Publications and source records attributed to J Ikebe.

14 recordsLinked to original sources
PubMed1990

New tetrapolar circuit method using magnetic field for measurement of local impedance change in biological substances.

A new tetrapolar circuit method using a magnetic field is proposed to measure the local electric impedance change in living tissue. Based on this method, we designed an apparatus which can detect impedance changes in closely-situated two parts of living tissue, simultaneously and independently. Using this apparatus, we showed the effectiveness of the proposed method by an in vitro experiment and by an in vivo measurement of pulsatile waveforms in the forearm arteries. The detection sensitivity for a local impedance change was confirmed to be higher than that of the conventional tetrapolar method. Pulsatile impedance waveforms measured in the radial and the ulnar parts of the forearm were consistent with those estimated from the anatomical structure.

Arteries↗
PubMed1989

[A tetrapolar circuit method using magnetic field for biological resistivity measurement].

A local impedance and its change were measured using a tetrapolar circuit combined with magnetic eddy current generator. By this method, current distribution can be restricted to a desired part, so as to eliminate errors due to uncertainty of the resistance between the electrode and the skin. The resistivity of a substance in a biological model measured by this method was nearly equal to that of the substance separated from the model. Sensitivity and localization were assessed in the other model composed of a piece of metal plate in a saline pool. The detection sensitivity was validated theoretically. The localization of the impedance pulsatile waveforms, measured at the proximal part of the forearm, was consistent with that of the arteries at this part. These results suggest that this method using eddy current should expand the application area of bio-impedance measurements.

Electric Conductivity↗
PubMed1975

Improvement of scintigram reliability by isocount scanning and multilevel analysis.

Given the target source conditions and the detector parameters, the isocount scanning uses optimally the available observation time by maintaining the statistical reliability of each measurement in the composition of a scintigram and by devoting all the observation time to the region of interest through logic circuits which allows quick skipping of the background region. The multilevel analysis is an effective enlargement of the dynamic range of the displayer screen density characteristics that emphasizes small uptake ratios in any density level. It also makes the features extraction very easy by producing an animated sequence of pictures of the observed organ on the screen. The detectability of small uptake ratios significantly improved, specially in regions of low counting rate where the fluctuation of data severely degrades the picture quality in the conventional constant speed scanning method.

Brain Neoplasms↗