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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 26-30 
    ISSN: 1741-0444
    Keywords: Impedance spectroscopy ; Tissue characterisation ; Data classification ; Discriminant analysis ; Breast cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Electrical impedance spectroscopy is a minimally invasive technique that has clear advantages for living tissue characterisation owing to its low cost and ease of use. The present paper describes how this technique can be applied to breast tissue classification and breast cancer detection. Statistical analysis is used to derive a set of rules based on features extracted from the graphical representation of electrical impedance spectra. These rules are used hierarchically to discriminate several classes of breast tissue. Results of statistical classification obtained from a data set of 106 cases representing six classes of excised breast tissue show an overall classification efficiency of ∼92% with carcinoma discrimination 〉86%.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 150-155 
    ISSN: 1741-0444
    Keywords: Ultrasound ; Electric conductivity ; Acoustic pressure ; Electrolyte solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The purpose of the study was the experimental assessment of the interaction coefficient characterising the influence of pressure on the conductivity of electrolyte solutions. Pressure pulses were applied to samples of 9 gl−1 sodium chloride contained in cuboid measurement cells of identical cross-sectional dimensions but different thickness along the acoustic beam axis. The magnitude of the changes induced in cell resistance was recorded for three values of applied pressure increment (ΔP=0.94, 1.39 and 1.78MPa) and three values of cell thickness (e=0.58, 1.13 and 1.62mm). A thick, focused transducer generated short (0.1μs), unipolar pressure pulses. A model accounting for the characteristics of the pressure pulse and the geometry of the measurement cell was developed to predict the ultrasound-dependent changes in the measured electrical resistance. Despite some discrepancy between theoretical and experimental results, discussed in the paper, the results validated the order of magnitude of the interaction coefficient (10−9 Pa−1). The predictions varied from about 50% (e=1.62 mm, ΔP=0.94MPa) to 77% (e=0.58mm, ΔP=1.78MPa) of the experimental values.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 427-432 
    ISSN: 1741-0444
    Keywords: Electrodes ; Electrolyte ; Interface impedance ; Transient response ; Nonlinearity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The voltage transient response, V(t), of the electrode—electrolyte interface is known to be nonlinear. It has been shown byOnaral andSchwan in 1983 that the DC limit current of linearity, IAL, is proportional to t−β were β is the fractional power dependence of the linear, short pulse duration impedance. We now seek to explain the physical phenomena underlying this observation. We present an equivalent circuit model of the interface and highlight the major source of the observed nonlinear behaviour. Using the equivalent circuit model and associated formulae, an expression for the limit current of linearity is derived and compared with that found experimentally byOnaral andSchwan. According to this theoretical model, a current of as little as 22nA can be sufficient to drive an electrode system into nonlinear behaviour at longer pulse durations.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 31 (1993), S. 318-322 
    ISSN: 1741-0444
    Keywords: Arterial walls ; Impedance plethysmography ; Limbs ; Noninvasive measurements ; Pulse-wave velocity ; Vascular assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 16 (1978), S. 459-470 
    ISSN: 1741-0444
    Keywords: Electrical impedance ; Respiration monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Depuis plusieurs années, nous avons utilisé les changements de l'impédance transthoracique pour étudier simultanément la ventilation des poumons et leur perfusion. Durant cette période, nous avons pu montre à la fois chez le poumon de chien transplanté (150 chiens) et chez l'homme (50 cas) des modifications caractéristiques de forme et d'amplitude. Pour pouvoir effectuer une étude plus précise des courbes enregistrées nous avons réalisé un dispositif spécial: un interface malade/ordinateur. Ce dispositif affiche immédiatement tous les paramètres importants des courbes de ventilation droite et gauche tels qu'amplitude, périodicité, temps d'expiration/inspiration, décalage entre la dilatation de la cage thoracique et les courbes de ventilation. De plus, nous avons calculé la courbe de perfusion moyenne par une méthode accumulative. Cela nous a permis d'obtenir les courbes de perfusion et de ventilation sans artéfacts.
    Abstract: Zusammenfassung Seit vielen Jahren haben wir die Eigenschaften der transthorakiscehn Impedanzveränderungen als Mittel für die Studien der simultanen Lungenventilation und-perfusion verwendet. Während dieser Periode gelang es uns, sowohl in verpflanzten Hundelungen (150 Hunde) als auch im Menschen (50) charakteristische Veränderungen der Form und Amplitude zu zeigen. Um eine noch präzisere Studie der aufgeichneten Kurven durchführen zu können, haben wir einen Speziallapparat gebaut—ein Patient-Computer-Kopplungssystem. Mit diesem Gerät werden sofort alle wichtigen Parameter der rechten und linken Ventilationskurven aufgezeichnet, wie z.B. Amplitude, Periode, Ausatmungs- und Einatmungszeit, Verschiebung zwischen der Brustkorbextension und den Ventilationskurven. Weiterhin kalkulieren wir die Durchsnittsperfusionskurve durch eine Sammelmethode. Dieses ermöglicht uns, Perfusions- und Ventilationskurven ohne Kunstprodukte herzustellen.
    Notes: Abstract For several years, we have been using the properties of transthoracic impedance modification as a means for studying simultaneously lung ventilation and perfusion. We have been able to show during this period, both in transplanted dog lung (150 dogs) and in man (50) characteristic modifications of form and amplitude. To carry out a more precise study of the recorded curves, we have built a special apparatus—a patient-computer interface. This device displays immediately all of the important parameters of the right and left ventilation curves; e.g. amplitude, period, expiration and inspiration time, shift between the extension of the rib cage and the ventilation curves. Furthermore, we calculate the mean perfusion curve by an accumulated method. This allows us to obtain perfusion and ventilation curves without artefacts.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 19 (1981), S. 419-425 
    ISSN: 1741-0444
    Keywords: Bioelectrical impedance ; Bubbles ; Decompression sickness ; Pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Symptoms that appear in the diver submitted to a fast decompression are known as decompression sickness. Rapid decompression causes bubbles of inert gases to form and grow within tissue or vascular space. Troubles only occur if bubbles are present in sufficient numbers. Ultrasonic Doppler techniques only permit the detection of great quantities of bubbles circulating in large vessels. A method using impedance measurement and the way to use it in hyperbaric fields are described. It allows the detection of tissular bubbles at an early stage by monitoring a muscular zone. The results obtained in the animal during traumatic decompressions and the initial results obtained in man during three experimental dives up to a simulated depth of 180 m of seawater shows a relationship between recorded impedance variations and the appearance of decompression sickness.
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  • 7
    Publication Date: 1994-05-01
    Print ISSN: 0967-3334
    Electronic ISSN: 1361-6579
    Topics: Medicine , Physics
    Published by Institute of Physics
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  • 8
    Publication Date: 1995-08-01
    Print ISSN: 0967-3334
    Electronic ISSN: 1361-6579
    Topics: Medicine , Physics
    Published by Institute of Physics
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  • 9
    Publication Date: 1994-05-01
    Print ISSN: 0967-3334
    Electronic ISSN: 1361-6579
    Topics: Medicine , Physics
    Published by Institute of Physics
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  • 10
    Publication Date: 1992-12-01
    Print ISSN: 0143-0815
    Topics: Medicine , Physics
    Published by Institute of Physics
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