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Induction powered biological radiosonde

  • US 4,186,749 A
  • Filed: 05/12/1977
  • Issued: 02/05/1980
  • Est. Priority Date: 05/12/1977
  • Status: Expired due to Term
First Claim
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1. A detector for measuring intracranial pressure at a subject'"'"'s dura and adapted to function in proximity to a source of electromagnetic energy, said detector comprising:

  • an oscillator with an L-C resonant circuit, said C of said resonant circuit comprising a capacitance-type pressure transducer, said transducer having a first electrode comprising a pressure-responsive diaphragm and a second fixed electrode opposite said first electrode, said diaphragm being a stiff metal disc hermetically sealed to one end of a metal tubular body, said diaphragm having a stiffness at least as great as 10 torr per micron, the frequency of said oscillator being the direct function of the intracranial pressure sensed by said diaphragm when said diaphragm contacts said subject'"'"'s dura;

    a second resonant circuit having a data transmitting coil and a capacitor;

    a buffer having an input with a high impedance and an output with a low impedance, said oscillator being coupled to said buffer input and said data transmitting coil being coupled to said buffer output;

    a cylindrically-shaped metal housing having a band of threads on the outer surface thereof said housing having a diameter larger than said transducer, said transducer being sealed to one end of said housing with said diaphragm and part of said tubular body projecting outside of said housing, the housing surrounding said transducer forming a shoulder, said diaphragm being a distance X from said shoulder, means for sealing the other end of said housing, said oscillator, said capacitor of said second resonant circuit, said buffer and said converting means all being hermetically sealed within said metal housing;

    a collar with internal threads;

    means for fastening said collar to a patient'"'"'s cranium;

    a sleeve with external and internal threads, said external threads adapted to mate with said collar threads, said internal threads adapted to mate with said housing threads, said sleeve having an end plate with an inner and an outer surface and a centrally located aperture slightly larger than said diaphragm, said aperture permitting a user to see when said sleeve has been advanced in said collar to the position where the end plate outer surface is flush with said subject'"'"'s dura, said end plate being X thick so that said transducer diaphragm will be flush to said outer surface of said sleeve and plate when said housing is screwed all the way into said sleeve and said shoulder touches said inner surface.

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