Implants using ultrasonic backscatter for sensing electrical impedance of tissue

Patent metadata

Field	Value
Publication number	US-11607128-B2
Application number	US-201716313860-A
Country	US
Kind code	B2
Filing date	Jul 7, 2017
Priority date	Jul 7, 2016
Publication date	Mar 21, 2023
Grant date	Mar 21, 2023

Abstract

Described herein is an implantable device configured to detect impedance characteristic of a tissue. In certain exemplary devices, the implantable device comprises (a) an ultrasonic transducer configured to emit an ultrasonic backscatter encoding information relating to an impedance characteristic of a tissue based on a modulated current flowing through the ultrasonic transducer; (b) an integrated circuit comprising (i) a variable frequency power supply electrically connected to a first electrode and a second electrode; (ii) a signal detector configured to detect an impedance, voltage, or current in a circuit comprising the variable frequency power supply, the first electrode, the second electrode, and the tissue; and (iii) a modulation circuit configured to modulate the current flowing through the ultrasonic transducer based on the detected impedance, voltage, or current; and the first electrode and the second electrode configured to be implanted into the tissue in electrical connection with each other through the tissue. Further described are systems including one or more implantable devices and an interrogator for operating the implantable device, methods of measuring impedance characteristic of a tissue in a subject, and methods of monitoring or characterizing a tissue in a subject.

First claim

The invention claimed is:

1. An implantable device, comprising:
a body 5 mm or less in length in the longest dimension, comprising:
(a) an ultrasonic transducer configured to emit an ultrasonic backscatter encoding information relating to an impedance characteristic of a tissue at a plurality of different signal source frequencies based on a modulated current flowing through the ultrasonic transducer; and
(b) an integrated circuit comprising:
(i) a variable frequency signal source circuit electrically connected to a first electrode and a second electrode, wherein the first electrode and the second electrode are configured to be in electrical connection with each other through the tissue, and wherein the variable frequency signal source circuit is configured to apply a current or voltage through the tissue at the plurality of different signal source frequencies;
(ii) a signal detector configured to detect, at the plurality of different signal source frequencies, an impedance, voltage, or current in a circuit comprising the variable frequency signal source circuit, the first electrode, the second electrode, and the tissue; and
(iii) a modulation circuit configured to modulate the current flowing through the ultrasonic transducer to cause the ultrasonic transducer to emit the ultrasonic backscatter encoding the information comprising the impedance characteristic of the tissue at the plurality of different signal source frequencies.

2. The implantable device of claim 1 , wherein the signal detector is electrically connected to the first electrode and the second electrode.

3. The implantable device of claim 1 , wherein the signal detector is electrically connected to a third electrode and a fourth electrode configured to be implanted into the tissue in electrical connection through the tissue.

4. The implantable device of claim 1 , wherein the signal detector is configured to detect one or more of an impedance magnitude and an impedance phase angle.

5. The implantable device of claim 1 , wherein the signal detector is configured to detect one or more of a voltage magnitude and a voltage phase.

6. The implantable device of claim 1 , wherein the signal detector is configured to detect one or more of a current magnitude and a current phase.

7. The implantable device of claim 1 , wherein the integrated circuit comprises a digital circuit configured to transmit a digital signal to the modulation circuit, and wherein the digital signal is based on the detected impedance, current, or voltage.

8. The implantable device of claim 1 , wherein the integrated circuit comprises one or more processors and a non-transitory computer-readable storage medium storing one or more programs configured to be executed by the one or more processors, the one or more programs comprising instructions for determining the impedance characteristic of the tissue based on the detected current or voltage.

9. The implantable device of claim 1 , wherein the integrated circuit comprises one or more processors and a non-transitory computer-readable storage medium storing one or more programs configured to be executed by the one or more processors, the one or more programs comprising instructions for determining one or more of an impedance magnitude and an impedance phase angle.

10. The implantable device of claim 1 , wherein the ultrasonic backscatter encodes one or more of an impedance magnitude and an impedance phase angle.

11. The implantable device of claim 1 , wherein the ultrasonic backscatter encodes an impedance magnitude spectrum comprising one or more of a plurality of impedance magnitude measurements taken at different current frequencies and a plurality of impedance phase angle measurements taken at different current frequencies.

12. The implantable device of claim 1 , wherein the integrated circuit comprises a power circuit.

13. The implantable device of claim 1 , wherein the integrated circuit comprises an analog-to-digital converter (ADC).

14. The implantable device of claim 1 , wherein the variable frequency signal source circuit is configured to supply a current to the tissue at a plurality of different signal frequencies at 10 Hz or more.

15. The implantable device of claim 1 , wherein the body has a volume of 5 mm 3 or less.

16. The implantable device of claim 1 , wherein the ultrasonic transducer is configured to receive ultrasonic waves that power the implantable device.

17. The implantable device of claim 1 , wherein the ultrasonic transducer is configured to receive ultrasonic waves that encode instructions for selecting a current frequency.

18. The implantable device of claim 1 , wherein the ultrasonic transducer is configured to receive ultrasonic waves from an interrogator comprising one or more ultrasonic transducers.

19. The implantable device of claim 1 , wherein the ultrasonic transducer is a bulk piezoelectric transducer, a piezoelectric micro-machined ultrasonic transducer (PMUT), or a capacitive micro-machined ultrasonic transducer (CMUT).

20. The implantable device of claim 1 , wherein the implantable device is implanted in a subject.

21. The implantable device of claim 20 , wherein the subject is a human.

22. The implantable device of claim 1 , wherein the implanted device is at least partially encapsulated by a biocompatible material.

Assignees

• Univ California

Inventors

• Maharbiz Michel M
• Carmena Jose M
• Seo Dongjin
• Lin Monica
• Marmor Meir
• Herfat Safa
• Bahney Chelsea Shields

Classifications

• A61B8/12

  in body cavities or body tracts, e.g. by using catheters · CPC title

• A61B8/56

  Details of data transmission or power supply · CPC title

• A61B8/04

  Measuring blood pressure · CPC title

• A61B8/4483

  characterised by features of the ultrasound transducer · CPC title

• A61B8/00

  Diagnosis using ultrasonic, sonic or infrasonic waves · CPC title