Induction powered biological radiosonde
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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Abstract
An induction powered implanted monitor for epidurally measuring intracranial pressure and telemetering the pressure information to a remote readout. The monitor utilizes an L-C oscillator in which the C comprises a variable capacitance transducer, one electrode of which is a small stiff pressure responsive diaphragm. The oscillator is isolated from a transmitting tank circuit by a buffer circuit and all electric components in the implanted unit except an input and an output coil are shielded by a metal housing.
201 Citations
2 Claims
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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:
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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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2. A detector for measuring intracranial pressure and adapted to function in proximity to an energizer radiating electromagnetic energy, said detector comprising:
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an oscillator with an L-C circuit, said C of said tank circuit comprising a variable capacitor having a fixed electrode and a movable electrode that is a stiff pressure-responsive diaphragm, the frequency of said oscillator being representative of the pressure sensed by said diaphragm; a second resonant circuit having a data transmitting coil and a parallel-coupled 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 second resonant circuit being coupled to said buffer output; an energy receiving coil for receiving said electromagnetic energy; means coupled to said energy receiving coil for converting said electromagnetic energy to a regulated supply voltage for said oscillator and said buffer; a cylindrically-shaped metal housing having first and second ends disposed on the longitudinal axis of said housing, said transducer being sealed to said first end with said diaphragm normal to said axis and displaced outwardly from said housing; said oscillator, said parallel-coupled capacitor, said buffer, and said energy converting means being sealed within said metal housing, a glass-to-metal seal situated in said second housing end; a plastic disc fastened to said second housing end and disposed normal to said housing axis, said coils being concentrically arranged and imbedded in said disc, the ends of said data transmitting coil passing through said glass-to-metal seal to said parallel-coupled capacitor, and the ends of said energy receiving coil passing through said glass-to-metal seal to said energy converting means; and means for supporting said metal housing on a patient'"'"'s cranium, said supporting means enabling said transducer diaphragm to be coplanar with the patient'"'"'s dura.
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Specification