Implantable transducer devices

• US 20060136005A1
• Filed: 12/21/2005
• Published: 06/22/2006
• Est. Priority Date: 12/21/2004
• Status: Active Grant

• Current Assignee: EBR Systems, Inc.
• Original Assignee: EBR Systems, Inc.
• Inventors: Riley, Richard E., Cowan, Mark W., Brisken, Axel F., Echt, Debra S.
• Granted Patent: US 7,606,621 B2
• Time in Patent Office: Days
• US Class Current: 607/33
• CPC Class Codes: A61N 1/362 Heart stimulators heart defibrillators A61N1/39
• CPC Class Codes: A61N 1/37205 Microstimulators, e.g. implantable through a cannula
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

Receiver-stimulators comprise a nearly isotropic transducer assembly, demodulator circuitry, and at least two tissue contacting electrodes. Use of near isotropic transducers allows the devices to be implanted with less concern regarding the orientation relative to an acoustic energy source. Transducers or transducer elements having relatively small sizes, typically less than ½ the wavelength of the acoustic source, enhance isotropy. The use of single crystal piezoelectric materials enhance sensitivity.

Claims

1. An implantable receiver-stimulator device comprising:

an isotropic transducer assembly which receives acoustic energy from an acoustic source and which produces an electrical signal in response to the acoustic energy;

demodulator circuitry which receives the electrical signal and which produces a biologically stimulating electrical output; and

at least two tissue contacting electrodes which receive the stimulating electrical output and deliver said output to tissue.

2. An implantable receiver-stimulator as in claim 1, wherein the electric signal produced by the transducer assembly in response to the acoustic energy varies by no more than ±

6 dB as the orientation relative to an acoustic source varies.

3. An implantable receiver-stimulator as in claim 1, wherein the electric signal produced by the transducer assembly in response to the acoustic energy varies by no more than ±

3 dB as the orientation relative to an acoustic source varies.

4. A device as in claim 1, wherein the transducer assembly comprises a piezoelectric transducer material.

5. A device as in claim 4, wherein piezoelectric transducer material is composed of a polycrystalline ceramic piezoelectric material or is composed of a single crystal piezoelectric material.

6. A device as in claim 4, wherein the transducer assembly comprises a cylindrical piezoelectric transducer having a pair of electrodes formed over opposed surfaces thereof.

7. A device as in claim 6, wherein the opposed electrodes are formed over outer and inner cylindrical surfaces.

8. A device as in claim 6, wherein the piezoelectric transducer composed of a single crystal piezoelectric material is cut in the <

001>

or <

011>

orientation.

9. A device as in claim 8, wherein the opposed electrodes are formed over the flat end surfaces of the cylinder.

10. A device as in claim 4, wherein the transducer assembly comprises a transducer composed of a single crystal cut in the <

001>

or <

011>

orientation.

11. A device as in claim 1, wherein the transducer assembly comprises a transducer composed of a single crystal material of the PMN-xPT family, where x is in the range from 5% to 50%.

12. A device as in claim 1, wherein the transducer assembly comprises a transducer composed of a single crystal material of the PZN-xPT family, where x is in the range from 5% to 50%.

13. A device as in claim 1, wherein the transducer assembly comprises a transducer composed of a single crystal material of the Relaxor-PT family.

14. A device as in claim 5, wherein the acoustic source transmits the acoustic energy at a frequency selected to match the lower frequency resonance of the piezoelectric transducer material composed of the single crystal piezoelectric material.

15. A device as in claim 1, wherein the transducer assembly comprises a plurality of individual transducer elements and wherein the demodulator circuitry comprises a plurality of individual demodulator circuits, with the electrical signal from each transducer element going to a demodulator circuit which produces an output, further comprising summing circuitry which sums all of the electrical signals from all of the demodulator circuits to produce the biologically stimulating electrical output.

16. A device as in claim 15, wherein the electrical signals are summed in parallel.

17. A device as in claim 15, wherein the electrical signals are summed in series.

18. A device as in claim 15, wherein the electrical signals are summed in a series-parallel combination.

19. A device as in claim 15, wherein the transducer elements each have a size less than one-half the wavelength of an acoustic source while collectively having a size greater than one wavelength in any lateral dimension.

20. A device as in claim 1, further comprising a shell having a wall surrounding an interior volume, wherein the transducer assembly and demodulator circuitry are within the interior volume and wherein at least a portion of the wall is acoustically transmissive.

21. A device as in claim 20, wherein the entire shell is acoustically transmissive.

22. A device as in claim 21, wherein the shell is cylindrical.

23. A device as in claim 22, wherein the shell has a diameter less than 5.0 mm and a length less than 20.0 mm more preferably a diameter less than 3.0 mm and a length less than 10.0 mm.

24. A method for delivering energy to an implanted receiver-stimulator, said method comprising:

implanting a receiver-stimulator having a transducer assembly;

directing acoustic energy to the implanted receiver-stimulator assembly from an acoustic source, wherein the transducer produces an electrical signal which varies by no more than ±

6 dB as the orientation of the transducer relative to the source varies;

demodulating the electrical signal to produce a biologically stimulating electrical output; and

delivering the electrical output to tissue.

25. A method as in claim 24, wherein the transducer assembly is adapted to receive acoustic energy in a substantially isotropic manner.

26. A method as in claim 24, wherein the acoustic energy is directed to the receiver-stimulator from an external acoustic source.

27. A method as in claim 24, wherein the acoustic energy is directed to the receiver-stimulator from an implanted acoustic source.

28. A method as in claim 24, wherein the electrical output comprises a cardiac pacing waveform.