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Non-invasive electromagnetic technique for monitoring time-trends of physiological changes at a particular location in the brain

  • US 4,819,648 A
  • Filed: 09/01/1987
  • Issued: 04/11/1989
  • Est. Priority Date: 10/28/1985
  • Status: Expired due to Term
First Claim
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1. An apparatus for sensing physiological changes in an animal or human brain, comprising:

  • a coil adapted to generate a magnetic field in a selected portion of a patient'"'"'s brain;

    a pad which is adapted to be placed on a patient'"'"'s head over a selected localized site, wherein said coil is mounted in said pad;

    an oscillator/detector means for exciting said coil with a time-varying electrical signal, for detecting changes in mutual inductance of said coil, and for outputting an information signal corresponding to such detected changes in mutual inductance, wherein changes in mutual inductance are caused by a secondary induced magnetic field which varies in response to the impedance of brain matter and fluid located in said selected portion of the patient'"'"'s brain;

    a calibration means for exciting said coil with a calibration current having a set value;

    a controller and data memory means for periodically actuating said calibration means and for storing values for said information signal, wherein calibration data is stored when said calibration means is actuated, and measurement data is stored when said calibration means is off;

    a means for correcting said measurement data for drift and background noise based on calibration data; and

    , a display means for displaying corrected measurement data.

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