Implant for in-vivo parameter monitoring, processing and transmitting

• US 7,621,878 B2
• Filed: 02/24/2003
• Issued: 11/24/2009
• Est. Priority Date: 09/24/1999
• Status: Expired due to Fees

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Ericson, Milton N., Hylton, James O., Smith, Stephen F., McKnight, Timothy E.
• Primary Examiner(s): Hindenburg; Max
• Assistant Examiner(s): HOEKSTRA, JEFFREY GERBEN
• Application Number:
  US10/374,928
• Publication Number:
  US 20030216666A1
• Time in Patent Office: 2,465 Days
• Field of Search: 600/300, 600/561, 600/587, 128/903
• US Class Current: 600/561
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61M 27/006 Cerebrospinal drainage; Accessories therefor, e.g. valves
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

The present invention relates to a completely implantable intracranial pressure monitor, which can couple to existing fluid shunting systems as well as other internal monitoring probes. The implant sensor produces an analog data signal which is then converted electronically to a digital pulse by generation of a spreading code signal and then transmitted to a location outside the patient by a radio-frequency transmitter to an external receiver. The implanted device can receive power from an internal source as well as an inductive external source. Remote control of the implant is also provided by a control receiver which passes commands from an external source to the implant system logic. Alarm parameters can be programmed into the device which are capable of producing an audible or visual alarm signal. The utility of the monitor can be greatly expanded by using multiple pressure sensors simultaneously or by combining sensors of various physiological types.

Claims

1. An implant for monitoring intracranial cerebral spinal fluid pressure of a subject, comprising:

a pressure transducer having a deflectable membrane separating a reference chamber and a local intracranial pressure chamber, the local intracranial pressure chamber in fluid communication with a shunt to receive cerebral spinal fluid, wherein a deflection of the deflectable membrane indicates a pressure differential between the reference chamber and the local intracranial pressure chamber, the deflection being measured by a strain measurement means, the pressure transducer configured to generate a signal representing the measured deflection;

a system controller coupled to the pressure transducer, the system controller including a processor configured to receive and process the generated signal and a transmitter configured to wirelessly transmit said processed signal;

a power source coupled to the system controller and configured to power said system controller, wherein the power source includes an energy storage device and an inductive coil; and

a single housing adapted to fully enclose the pressure transducer, the system controller, the energy storage device and the inductive coil and sized to be fully implanted at a single location surrounding the shunt within a head of said subject,

wherein the inductive coil is configured to receive inductive power from an inductive power source positioned outside the single housing, the inductive power source operable to induce current in said inductive coil to recharge the energy storage device and power the system controller.

2. The implant of claim 1, further comprising a power managing circuit included in the single housing and coupled to the power source and configured to regulate operation of the power source.

3. The implant of claim 2, wherein the power managing circuit is configured to monitor power consumption levels of the implant.

4. The implant of claim 2, wherein said processor performs the following functions to regulate operation of the power source, including:

enabling the energy storage device to power the system controller in the absence of inductive power; and

selectively enabling inductive power induced in the inductive coil to recharge the energy storage device and power the system controller during wireless transmittal of data from the system controller to a monitoring device external to the single housing.

5. The implant of claim 2, wherein the power managing circuit is configured to monitor at least one of a charge of the energy storage device and a voltage of the power source.

6. The implant of claim 2, wherein the inductive power source includes an energizing coil and a driving circuit having an impedance.

7. The implant of claim 6, wherein the power managing circuit includes a matching circuit having an impedance, wherein the impedance of the matching circuit is configured to optimally match the impedance of the driving circuit of the inductive power source.

8. The implant of claim 2, wherein the power managing circuit is coupled to the system controller and configured to monitor a charge of the energy storage device and a voltage of the power source.

9. The implant of claim 8, wherein the inductive power source is configured to automatically trigger the system controller to wirelessly transmit data representing the charge of the energy storage device and the voltage of the power source via said transmitter.

10. The implant of claim 8, wherein the inductive power source is configured to automatically trigger the system controller to wirelessly transmit data representing the pressure of the cerebral spinal fluid via said transmitter.

11. The implant of claim 1, wherein the inductive coil comprises a planarized coil disposed along a perimeter of the implant to minimize the overall size of the implant.

12. The implant of claim 1, wherein the inductive power of the inductive coil of the power source has a resonant frequency in a range of 100 kHz to 1 MHz.

13. The implant of claim 1, wherein the energy storage device comprises a battery and a capacitive device coupled to the battery.

14. The implant of claim 1, wherein the power source includes a capacitive device.

15. The implant of claim 1, further comprising an antenna included in the single housing and coupled to the system controller, the antenna configured to transmit and receive data.

16. The implant of claim 1, wherein the transmitter is configured to wirelessly transmit a command signal to a shunt valve external to the single housing and coupled to the shunt, the shunt valve operable to shunt cerebral spinal fluid away from a ventricle of the head of said subject.

17. The implant of claim 16, wherein only the energy storage device is operable to power the system controller to monitor the cerebral spinal fluid pressure and transmit the command signal to the shunt valve to compensate for fluctuations in pressure in the absence of inductive power.

18. The implant of claim 1, wherein the inductive power induced in the inductive coil is selectively enabled to recharge the energy storage device and power the system controller during wireless transmittal of data from the system controller to a monitoring device external to the single housing.

19. The implant of claim 1, wherein the pressure transducer includes a plurality of pressure transducers each coupled to the shunt to receive cerebral spinal fluid, and wherein said processor is configured to evaluate the performance of the pressure transducers and detect degradation of the pressure transducers.

20. The implant of claim 19, wherein said processor performs the following functions to evaluate the performance of the pressure transducers and detect degradation of the pressure transducers, including:

performing standard-deviation calculations of the deflection of the deflectable membrane of each of the plurality of pressure transducers;

determining an average of the deflection of the deflectable membrane of each of the plurality of pressure transducers;

determining the differential over time of the deflection of the deflectable membrane of each of the plurality of pressure transducers; and

determining the minimum and maximum of the deflection of the deflectable membrane of each of the plurality of pressure transducers.

21. An implant for monitoring intracranial cerebral spinal fluid pressure of a subject, comprising:

a pressure transducer coupled to a shunt and configured to generate a signal representing said intracranial cerebral spinal fluid pressure;

a system controller coupled to the pressure transducer, the system controller including a processor configured to receive and process the generated signal and a hybrid spread-spectrum transmitter configured to wirelessly transmit said processed signal, the hybrid spread-spectrum transmitter including a spread-spectrum modulation configured to generate a spreading-code signal and to reduce substantially all multi-path reflection errors, wherein the spread-spectrum modulation comprises direct-sequence modulation, frequency-hopping modulation, and time-hopping modulation;

a power source coupled to the system controller and configured to power said system controller, wherein the power source includes an energy storage device and an inductive coil; and

a single housing adapted to fully enclose the pressure transducer, the system controller, the energy storage device and the inductive coil and sized to be fully implanted at a single location surrounding the shunt within a head of said subject,

wherein the inductive coil is configured to receive inductive power from an inductive power source positioned outside the single housing, the inductive power source operable to induce current in said inductive coil to recharge the energy storage device and power the system controller.

22. The implant of claim 21, wherein said hybrid spread-spectrum transmitter is a radio frequency transmitter configured to operate in a frequency including at least one of 902-928 MHz, 2450-2483.5 MHz, 5150-5250 MHz, and 57250-5825 MHz.

23. The implant of claim 21, wherein said hybrid spread-spectrum transmitter is a radio frequency transmitter configured to operate in a frequency greater than 1 GHz.

24. The implant of claim 21, wherein said hybrid spread-spectrum transmitter is an ultrasonic transmitter.

25. The implant of claim 21, wherein said transmitter is configured to transmit a processed signal through multiple-access spread-spectrum transmission including code division, frequency-division and time division multiplexing.

26. The implant of claim 21, further includes an monitoring device external to the single housing and having a receiver configured to receive said processed signal from the hybrid spread-spectrum transmitter.

27. The implant of claim 26, wherein said receiver includes an audible or visual alarm configured to activate upon receipt of said processed signal outside a predetermined tolerance range.

28. The implant of claim 26, wherein the transmitter is configured to wirelessly transmit a command signal to a shunt valve external to the single housing and coupled to the shunt, the shunt valve operable to shunt cerebral spinal fluid away from a ventricle of the head of said subject.

29. The implant of claim 28, wherein only the energy storage device is operable to power the system controller to monitor the cerebral spinal fluid pressure and transmit the command signal to the shunt valve to compensate for fluctuations in pressure in the absence of inductive power.

30. The implant of claim 29, the inductive power induced in the inductive coil is selectively enabled to recharge the energy storage device and power the system controller during wireless transmittal of data from the system controller to a monitoring device external to the single housing.

31. The implant of claim 21, further comprising a plurality of sensors included in the single housing and coupled to the system controller, wherein the sensors are configured to sense physiological parameters.