IMPLANTABLE PRESSURE SENSOR

• US 20130303942A1
• Filed: 05/08/2013
• Published: 11/14/2013
• Est. Priority Date: 05/08/2012
• Status: Active Grant

• Current Assignee: Case Western Reserve University, Cleveland Clinic Foundation, US Department of Veterans Affairs (Government of the United States of America)
• Original Assignee: Case Western Reserve University, Cleveland Clinic Foundation
• Inventors: Fletter, Paul C., Zaszczurynski, Paul, Damaser, Margot S., Majerus, Steven, Garverick, Steven L., Wen, Ko
• Granted Patent: US 10,143,391 B2
• Time in Patent Office: Days
• US Class Current: 600/561
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: A61B 5/205 Determining bladder or urethral pressure
• CPC Class Codes: A61B 5/6874 Bladder
• CPC Class Codes: A61B 5/6882 Anchoring means
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

Systems and methods are provided for in vivo measurement of pressure. An implantable sensor assembly includes a pressure sensor configured to provide an analog signal representing pressure and a signal conditioning component configured to convert the pressure sensor output into a digital signal. A transmitter is configured to transmit the digital signal to an external base unit. A power control unit is configured to dynamically allocate power throughout the implantable sensor assembly, such that during an active measurement interval of the implantable sensor assembly, each of the pressure sensor, the signal conditioning component, and the transmitter are powered only for a portion of the active measurement interval necessary to perform a related function.

Claims

1. An in vivo sensor assembly comprising:

a pressure sensor configured to provide an analog signal representing pressure;

a signal conditioning component configured to convert the pressure sensor output into a digital signal;

a transmitter configured to transmit the digital signal to an external base unit; and

a power control unit configured to dynamically allocate power throughout the implantable sensor assembly, such that during an active measurement interval of the implantable sensor assembly, each of the pressure sensor, the signal conditioning component, and the transmitter are powered only for a portion of the active measurement interval necessary to perform a related function.

2. The in vivo sensor assembly of claim 1, wherein the active measurement interval has a duration of approximately one millisecond, and the power control unit being further configured to provide the active measurement interval with a frequency between twenty and one hundred hertz.

3. The in vivo sensor assembly of claim 1, wherein the signal conditioning component comprises:

a preamplifier that amplifies an output of the pressure sensor; and

a differential correlated double-sampling amplifier arrangement that amplifies the output of the preamplifier.

4. The in vivo sensor assembly of claim 3, wherein the preamplifier is a chopper-stabilized, continuous time fully differential operational preamplifier.

5. The in vivo sensor assembly of claim 1, wherein the signal conditioning component comprises an offset removal component configured to calculate a correction value for the output of the pressure sensor as a function of an average of a predetermined number of previous samples.

6. The in vivo sensor assembly of claim 5, wherein the offset removal component calculates the correction value as a difference between the a full-scale range of a digital-to-analog converter associated with the transmitter and an average of a predetermined number of previous samples to maximize a sensing dynamic range of the in vivo sensor assembly.

7. The in vivo sensor assembly of claim 5, wherein the signal conditioning component comprises an offset removal component responsive to an external command, the offset removal component being configured to, in response to the external command, instruct the sensor to take a plurality of measurements over a short period of time, the signal offset component calculating a correction value as an average of the plurality of measurements as to null the system.

8. The in vivo sensor assembly of claim 1, wherein each of the signal conditioning component, the transmitter, and the power control unit are implemented as a single application-specific integrated circuit chip.

9. A pressure monitoring system comprising:

the in vivo sensor assembly of claim 1; and

the external base unit, the external base unit comprising;

a receiver configured to receive the digital signal from the transmitter; and

an event detection component configured to at least one predetermined physiological events in the received digital signal.

10. The pressure monitoring system of claim 9, the event detection component being configured to apply a multi-resolution wavelet analysis to the received digital signal to provide a transformed signal in a transform domain, identify clusters within the transform domain, and classify the digital signal into one of a plurality of event classes according to the identified clusters.

11. The pressure monitoring system of claim 9, wherein the external base unit comprises a recharger configured to transmit radio frequency (RF) energy, and the in vivo sensor assembly further comprises a microbattery and a recharge component configured to inductively charge the microbattery in the presence of the transmitted RF energy.

12. The pressure monitoring system of claim 11, wherein a transmitted power of the recharger is responsive to the digital signal.

13. The pressure monitoring system of claim 12, wherein the power control unit is configured to determine if the recharge component is receiving sufficient energy from the recharger, and the signal conditioning component being configured to encode a first binary value into a bit of the digital signal if sufficient power is being received, and a second binary value into the bit if sufficient power is not being received.

14. A pressure monitoring system comprising:

an implanted pressure sensor assembly comprising;

a pressure sensor configured to provide an analog signal representing pressure;

a signal conditioning component configured to convert the pressure sensor output into a digital signal;

a transmitter configured to transmit the digital signal to an external base unit;

a microbattery;

a power control unit configured to dynamically allocate power from the microbattery throughout the implantable sensor assembly; and

a recharge component configured to inductively charge the microbattery in the presence of the transmitted radio frequency (RF) energy; and

an external base unit comprising;

a receiver configured to receive the digital signal from the transmitter; and

a recharger configured to transmit RF energy to the recharge component, a transmitted power of the recharger being responsive to the digital signal.

15. The system of claim 14, wherein the power control unit is configured to allocate power throughout the implantable sensor assembly such that during an active measurement interval of the implantable sensor assembly, each of the pressure sensor, the signal conditioning component, and the transmitter are powered only for a portion of the active measurement interval necessary to perform a related function.

16. The system of claim 14, the external base unit comprising an event detection component configured to apply a multi-resolution wavelet analysis to the received digital signal to provide a transformed signal in a transform domain, identify clusters within the transform domain, and classify the digital signal into one of a plurality of event classes according to the identified clusters.

17. A method for determining a pressure from an in vivo sensor comprising:

receiving a digital signal from the in vivo sensor;

applying a windowing function to the digital signal to isolate a portion of the digital signal representing a series of pressure measurements;

applying a multi-resolution wavelet analysis to the isolated portion of the digital signal to provide a transformed signal;

extracting classification features from the transformed signal; and

classifying the signal into one of a plurality of event classes according to the extracted classification features.

18. The method of claim 17, further comprising transmitting radio frequency (RF) energy to the in vivo sensor to recharge an associated battery, with a power of the transmitted energy being responsive to the digital signal.

19. The method of claim 17, the method further comprising transmitting the digital signal during an active measurement interval of the in vivo sensor such that power is dynamically allocated during the active measurement interval of the implantable sensor assembly, with each of a pressure sensor assembly, a signal conditioning component, and a transmitter of the in vivo sensor powered only for a portion of the active measurement interval necessary to perform a related function.

20. The method of claim 17, wherein extracting classification features from the transformed signal comprises identifying clusters within the transform domain.