System for transcutaneous monitoring of intracranial pressure
First Claim
1. An implantable biometric sensor comprising:
- a subcutaneous case;
an access portal in the case to an internal fluid;
a sensor within the case generating a signal related to a property of the internal fluid;
a conversion circuit within the case transforming the signal into a transmitted near infrared optical form; and
an inductive power coupling providing power to the sensor and the conversion circuit; and
,the sensor is an oscillated crystal comparator further comprisingan isolated reference crystal exposed to a reference pressure and connected to a reference oscillator;
wherein said reference crystal produces a first frequency signal upon excitement thereof;
a transducer crystal exposed to said internal fluid and connected to a transducer oscillator;
wherein said transducer crystal produces a second frequency signal upon excitement thereof;
a heterodyne amplifier connected to the transducer oscillator and the reference oscillator to generate a frequency difference between the first frequency signal and the second frequency signal to compute said property of said internal fluid.
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Abstract
A system for measuring and converting to an observer intelligible form an internal physiological parameter of a medical patient. The invention allows transcutaneous telemetry of the measured information intracranial pressure via a system which includes a patient implanted sensor module and a processing and display module which is external of the patient and optically coupled to the sensor module via an external coupling module. A sensor within the implanted module transduces the measured information and a near infrared (NIR) emitter transmits this telemetry information when interrogated by the complementary external coupling module. Alternately, a set of tuned inductor-crystal circuits versus inductor-crystal comprised in part of a cylindrical crystal oscillator whose resonant frequency is sensed by a dipper circuit arrangement is provided. Power for the sensor module is derived inductively through rectification of a transcutaneously-applied high-frequency alternating electromagnetic field which is generated by a power source within the external coupling module, in concept much like a conventional electrical transformer. A computer within the processing and display module calculates the parameter value from the telemetry signal and represents this data either in numerical, graphical, or analog format.
30 Citations
23 Claims
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1. An implantable biometric sensor comprising:
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a subcutaneous case; an access portal in the case to an internal fluid; a sensor within the case generating a signal related to a property of the internal fluid; a conversion circuit within the case transforming the signal into a transmitted near infrared optical form; and an inductive power coupling providing power to the sensor and the conversion circuit; and
,the sensor is an oscillated crystal comparator further comprising an isolated reference crystal exposed to a reference pressure and connected to a reference oscillator;
wherein said reference crystal produces a first frequency signal upon excitement thereof;a transducer crystal exposed to said internal fluid and connected to a transducer oscillator;
wherein said transducer crystal produces a second frequency signal upon excitement thereof;a heterodyne amplifier connected to the transducer oscillator and the reference oscillator to generate a frequency difference between the first frequency signal and the second frequency signal to compute said property of said internal fluid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification