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  • 1
    Electronic Resource
    Electronic Resource
    Noninvasive detection of ventricular wall motion by electromagnetic coupling (1991)
    Springer
    Medical & biological engineering & computing 29 (1991), S. 136-140 
    Details
    ISSN: 1741-0444
    Keywords: Cardiokymography ; Electromagnetic coupling ; Lossy dielectric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Radiofrequency coils are used as sensors in various applications such as nuclear magnetic resonance (NMR) imaging and displacement cardiograms (DCGs). In most cases the impedance and the resonant frequency of the coil are monitored to provide the required information. The paper describes the changes in reflected impedance and in resonant frequency of a coil when it is placed near a medium with properties ranging from a lossy dielectric to a pure conductor. The theory of interaction between the coil and the medium is investigated and a model based on the use of vector potentials is developed. One prediction of the theory is that placing the coil over body equivalent saline (lossy dielectric) at 15 MHz results in an increase in the inductance of the coil and a resultant decrease in resonant frequency. This prediction was supported experimentally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02447098
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Noninvasive detection of ventricular wall motion by electromagnetic coupling (1991)
    Springer
    Medical & biological engineering & computing 29 (1991), S. 141-148 
    Details
    ISSN: 1741-0444
    Keywords: Cardiokymography ; Electromagnetic coupling ; Left and right ventricular wall motion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The cardiokymograph or displacement cardiograph (DCG) is a non-contacting device which senses movement of the heart throughout the cardiac cycle by the interaction of a radiofrequency (10–20 MHz) electromagnetic field, generated by a sensing coil, with the thorax. In the paper three different techniques of detecting this movement will be discussed: monitoring the changes in sensing resonant frequency (FM modulation), monitoring the changes in impedance of the coil at resonant frequency (AM modulation) and a new technique which monitors the changes in coil impedance at fixed frequency. The sensitivities of these three techniques will be compared. A simplified theory of the mode of coupling between the coil and the thorax will be studied in terms of a transformer model. Preliminary clinical measurements of anterior left and right ventricular motion will be given. The presence of higher-frequency features related to atrial motion and the opening and closing of the aortic and pulmonary values will also be described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02447099
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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