Passive Wireless Gastroesophageal Sensor

• US 20080234599A1
• Filed: 03/24/2008
• Published: 09/25/2008
• Est. Priority Date: 03/24/2007
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Chiao, Jung-Chih, Ativanichayaphong, Thermpon
• Granted Patent: US 8,706,208 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/4233 oesophagus

Abstract

A passive wireless gastroesophageal sensor includes a LC resonance circuit, two or more electrodes and a passive batteryless Radio Frequency Identification (RFID) circuit connected to the LC resonance circuit and the one or more electrodes. The electrodes are configured to measure an impedance within a gastroesophageal tract. The passive batteryless RFID circuit transmits a frequency modulated signal using the LC resonance circuit that varies between a first frequency corresponding to a non-acid reflux condition and a second frequency corresponding to an acid reflux condition based on the measured impedance in response to a signal received from a detector.

Claims

1. A passive wireless gastroesophageal sensor comprising:

a LC resonance circuit;

two or more electrodes configured to measure an impedance within a gastroesophageal tract; and

a passive batteryless Radio Frequency Identification (RFID) circuit connected to the LC resonance circuit and the one or more electrodes to transmit a frequency modulated signal using the LC resonance circuit that varies between a first frequency corresponding to a non-acid reflux condition and a second frequency corresponding to an acid reflux condition based on the measured impedance in response to a signal received from a detector.

2. The sensor as recited in claim 1, wherein:

the non-acid reflux condition comprises a gas, air, food, drink, saliva or other substance before the substance has entered a stomach disposed on or between the electrodes; and

the acid reflux condition comprises a stomach acid or stomach contents disposed on or between the electrodes.

3. The sensor as recited in claim 1, wherein:

the first frequency comprises a measured frequency of between 6 kHz and 11 kHz; and

the second frequency comprises a measured frequency greater than 11 kHz.

4. The sensor as recited in claim 1, wherein:

the LC resonance circuit comprises a parallel connected antenna and a capacitor; and

the passive batteryless RFID circuit comprises a voltage regulator, a voltage multiplies connected to the voltage regulator, a transistor switch connected in parallel between the LC resonance circuit and the voltage multiplier, and an impedance to frequency converter connected the electrodes and the voltage regulator wherein the impedance to frequency converter controls the transistor switch.

5. The sensor as recited in claim 1, wherein the LC resonance circuit, the electrodes and the passive batteryless RFID circuit comprise the circuits illustrated in FIGS. 5, 6 and 7.

6. The sensor as recited in claim 1, wherein the sensor is configured as a capsule, a tag or an implant having an overall size equal to or less than 0.5×

1×

3 cm³.

7. The sensor as recited in claim 3, wherein the antenna comprises at least one wire coil surrounding the electrodes.

8. The sensor as recited in claim 6, wherein the wire coil comprises at least 15 turns of a conductor having a width of 200 μ

m and a spacing of 50-μ

m in each turn.

9. The sensor as recited in claim 1, wherein the electrodes comprises at least 10 interdigitated fingers that are about 0.4 mm wide and about 5 mm long with about 0.1 mm spacing there between.

10. The sensor as recited in claim 1, wherein the passive batteryless RFID circuit uses a frequency shift keying modulation to reduce noise.

11. The sensor as recited in claim 1, wherein the electrodes are fabricated by a process comprising the steps of:

evaporating a first conductive material on a flexible polyimide substrate;

patterning a photoresist layer on selected portions of the first conductive material;

electroplating the first conductive material;

removing the photoresist layer and etching the first conductive material to form the electrodes;

patterning an epoxy based negative resist layer; and

electroplating a second conductive material on the electrodes.

12. A system for detecting Gastroesophageal Reflux Disease (GERD) in an animal comprising:

a detector comprising;

an external resonance circuit formed from an external coil,

a power amplifier connected to the external resonance circuit,

a radio frequency source connected to the power amplifier,

an envelope detector connected to the power amplifer, and

a band pass filter connected to the envelope detector; and

one or more passive wireless gastroesophageal sensors, each sensor comprising;

a LC resonance circuit,

two or more electrodes configured to measure an impedance within a gastroesophageal tract, and

a passive batteryless Radio Frequency Identification (RFID) circuit connected to the LC resonance circuit and the one or more electrodes to transmit a frequency modulated signal using the LC resonance circuit that varies between a first frequency corresponding to a non-acid reflux condition and a second frequency corresponding to an acid reflux condition based on the measured impedance in response to a signal received from the detector.

13. The system as recited in claim 12, wherein the power amplifier comprises the circuit illustrated in FIG. 10 and the envelope detector comprises the circuit illustrated in FIG. 11.

14. The system as recited in claim 12, wherein:

the first frequency comprises a measured frequency of between 6 kHz and 11 kHz; and

the second frequency comprises a measured frequency greater than 11 kHz.

15. The system as recited in claim 12, wherein:

the LC resonance circuit comprises a parallel connected antenna and a capacitor; and

the passive batteryless RFID circuit comprises a voltage regulator, a voltage multiplies connected to the voltage regulator, a transistor switch connected in parallel between the LC resonance circuit and the voltage multiplier, and an impedance to frequency converter connected the electrodes and the voltage regulator wherein the impedance to frequency converter controls the transistor switch.

16. The system as recited in claim 12, wherein the one or more sensors comprise multiple sensors implanted to detect a refluxate in multiple areas of the gastroesophageal tract of the animal.

17. The system as recited in claim 12, wherein the electrodes are fabricated by a process comprising the steps of:

evaporating a first conductive material on a flexible polyimide substrate;

patterning a photoresist layer on selected portions of the first conductive material;

electroplating the first conductive material;

removing the photoresist layer and etching the first conductive material to form the electrodes;

patterning an epoxy based negative resist layer; and

electroplating a second conductive material on the electrodes.

18. The system as recited in claim 12, wherein the external resonance circuit is uniquely coupled to each sensor.

19. The system as recited in claim 12, wherein the external resonance circuit is uniquely coupled to more than one of the sensors.

20. The system as recited in claim 12, wherein the sensor comprises multiple sensors implanted to detect refluxate in multiple areas of the gastroesophageal system.

21. A method of wirelessly detecting a refluxate in the gastroesophageal system of an animal comprising the steps of:

(a) implanting in the gastroesophageal system of the animal an untethered sensor comprising;

a LC resonance circuit,

two or more electrodes configured to measure an impedance within the gastroesophageal tract, and

a passive batteryless Radio Frequency Identification (RFID) circuit connected to the LC resonance circuit and the one or more electrodes to transmit a frequency

modulated signal using the LC resonance circuit that varies between a first frequency corresponding to a non-acid reflux condition and a second frequency corresponding to an acid reflux condition based on the measured impedance in response to a signal received from a detector external to the animal;

(b) detecting the transmitted frequency using a detector comprising;

an external resonance circuit formed from an external coil,

a power amplifier connected to the external resonance circuit,

a radio frequency source connected to the power amplifier,

an envelope detector connected to the power amplifer, and

a band pass filter connected to the envelope detector; and

(c) determining an acidity of the refluxate based on the detected frequency.

22. The method as recited in claim 21, wherein:

the first frequency comprises a measured frequency of between 6 kHz and 11 kHz; and

the second frequency comprises a measured frequency greater than 11 kHz.

23. The method as recited in claim 21, wherein:

the LC resonance circuit comprises a parallel connected antenna and a capacitor; and

the passive batteryless RFID circuit comprises a voltage regulator, a voltage multiplies connected to the voltage regulator, a transistor switch connected in parallel between the LC resonance circuit and the voltage multiplier, and an impedance to frequency converter connected the electrodes and the voltage regulator wherein the impedance to frequency converter controls the transistor switch.