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US 4,265,252 AGranted
Intracranial pressure implant
AssigneeThe Johns Hopkins University
InventorsJohn G. Chubbuck, James T. Turner
Life of this patent
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AssigneeThe Johns Hopkins University
InventorsJohn G. Chubbuck, James T. Turner
Estimating the term…
An implantable transensor device containing a passive RF resonant circuit having a natural frequency influenced by the pressure of the sensor's environment in a body cavity of a living entity. The circuit of the transensor includes an inductor and a capacitor, at least one of which varies in value in direct relation to variation of environmental pressure to change the resonant frequency of the circuit. The circuit can be externally interrogated to determine the resonant frequency thereof at any point in time by the imposition thereon of swept frequency electromagnetic radiation provided by a monitoring device which determines when some of the radiation is absorbed as a result of the frequency of the radiation being the same as the resonant frequency of the transensor circuit. An imposed relationship exists between the sensed environmental pressure, and the reactance of the reactive components of the circuit. A natural relationship exists between pressure sensitive reactance, and the resonant frequency of the circuit. As a result, an increase in environmental pressure causes a corresponding increase in frequency and a decrease in environmental pressure causes a decrease in frequency.
An apparatus for sensing pressure within a cavity in the body of a living entity and for implantation within said body comprising:
In an apparatus for sensing pressure within a cavity in the body of a living entity having a housing for location within said cavity and a fixed inductor-variable capacitor circuit means whose resonant frequency shifts with changes in said pressure, said variable capacitor providing mechanically arrangeable means having a fixed portion and a moveable electrically conductive surface, said variable capacitor also providing a fixed electrically conductive surface, the improvement comprising, unitary rigid spacer means disposed between said fixed portion of said mechanically arrangeable means and said fixed electrically conductive surface, said spacer means comprising a unitary wall having a first and a second opposed edge lying, respectively, in first and second substantially parallel planes, said wall forming a substantially straight rigid support between said edges, said mechanically arrangeable means being fixedly secured to said first edge, said fixed electrically conductive surface being fixedly secured to said second edge, said unitary wall fixing the distance between said fixed portion of said mechanically arrangeable means and said fixed electrically conductive surface independent of said housing.
Dependencies are inferred from the claim text.