External charger for a medical implantable device using field inducing coils to improve coupling

• US 8,548,590 B2
• Filed: 10/16/2012
• Issued: 10/01/2013
• Est. Priority Date: 10/15/2009
• Status: Expired due to Fees

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Aghassian, Daniel
• Primary Examiner(s): GETZOW, SCOTT M
• Application Number:
  US13/653,185
• Publication Number:
  US 20130041429A1
• Time in Patent Office: 350 Days
• Field of Search: 607 29- 33, 607/61
• US Class Current: 607/33
• CPC Class Codes: A61N 1/36071 Pain
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

By incorporating magnetic field-inducing position determination coils (PDCs) in an external charger, it is possible to determine the position of an implantable device by actively inducing magnetic fields using the PDCs and sensing the reflected magnetic field from the implant. In one embodiment, the PDCs are driven by an AC power source with a frequency equal to the charging coil. In another embodiment, the PDCs are driven by an AC power source at a frequency different from that of the charging coil. By comparing the relative reflected magnetic field strengths at each of the PDCs, the position of the implant relative to the external charger can be determined. Audio and/or visual feedback can then be communicated to the patient to allow the patient to improve the alignment of the charger.

Claims

1. An external charger for providing power to an implantable medical device, comprising:

a plurality of position determination coils;

one or more current or voltage sources for driving the plurality of position determination coils to produce magnetic fields;

an alignment sensing circuit for determining an alignment of the external charger relative to the implantable medical device, wherein the determination is based on electrical measurements taken from the plurality of position determination coils; and

a position indication circuit for receiving the determination and for indicating to a user a misalignment of the external charger relative to the implantable medical device.

2. The external charger of claim 1, wherein the position indication circuit further indicates to the user how to improve the alignment of the external charger relative to the implantable medical device.

3. The external charger of claim 1, wherein the position indication circuit activates visual indicators on the external charger.

4. The external charger of claim 3, wherein the visual indicators indicate a direction in which the external charger should be moved to improve the alignment of the external charger relative to the implantable medical device.

5. The external charger of claim 1, wherein the alignment sensing circuit measures reflections of the magnetic fields from the implantable medical device.

6. The external charger of claim 1, wherein the electrical measurement comprises a voltage across at least one of the plurality of position determination coils.

7. The external charger of claim 1, wherein the electrical measurement comprises a current through at least one of the plurality of position determination coils.

8. The external charger of claim 1, further comprising a primary coil, the primary coil for providing the power to the implantable medical device, wherein the primary coil is wound around a central axis, and wherein the plurality of position determination coils are wound around axes that are parallel to the central axis.

9. The external charger of claim 1, further comprising a primary coil, the primary coil for providing the power to the implantable medical device, wherein the primary coil and the plurality of position determination coils are driven at different frequencies.

10. The external charger of claim 1, wherein the external charger comprises a plurality of current or voltage sources each for driving one of the position determination coils.

11. A method for providing power to an implantable medical device, comprising:

producing from each of a plurality of position determination coils a magnetic field, wherein the plurality of position determination coils comprise a portion of an external charger;

sensing reflections of the magnetic fields from the implantable medical device at the plurality of position determination coils; and

determining alignment of the external charger relative to the implantable medical device while the external charger provides power to the implantable medical device, wherein the determination is based on electrical measurements taken from the plurality of position determination coils.

12. The method of claim 11, further comprising transmitting to another external device an indication of how to improve the alignment of the external charger relative to the implantable medical device.

13. The method of claim 12, wherein the another external device comprises an external device for controlling the therapeutic settings of the implantable medical device.

14. The method of claim 11, further comprising indicating to a user how to move the external charger relative to the implantable medical device based on the determined alignment.

15. The method of claim 11, wherein the plurality of position determination coils comprises a first pair of coils and a second pair of coils, wherein the first pair of coils indicate the alignment with respect to a first direction, and wherein the second pair of coils indicate the alignment with respect to a second direction orthogonal to the first direction.

16. The method of claim 15, wherein determining the alignment comprises:

comparing voltages across each coil in the first pair to produce a first error indication with respect to the first direction, and

comparing voltages across each coil in the second pair to produce a second error indication with respect to the second direction.

17. The method of claim 11, wherein a primary coil for providing power to the implantable medical device and the plurality of position determination coils are driven at different frequencies.

18. The method of claim 11, wherein at least two of the plurality of position determination coils are each driven by a different current or voltage source.

19. The method of claim 11, wherein at least two of the plurality of position determination coils are each driven by the same current or voltage source.

20. The method of claim 11, wherein the electrical measurement is a voltage measurement.

21. The method of claim 11, wherein the electrical measurement is a simultaneous measurement of current or voltage at each of the plurality of position determination coils.

22. The method of claim 11, wherein the power provided to the implantable medical device is temporarily interrupted to make the electrical measurements.

23. A method for assessing alignment of an external charger relative to an implantable medical device, comprising:

producing from each of a plurality of position determination coils a magnetic field, wherein the plurality of position determination coils comprise a portion of an external charger;

measuring at the external charger the strength of the magnetic fields reflected from the implantable medical device; and

determining alignment of the external charger relative to the implantable medical device by comparing the strength of at least two of the reflected magnetic fields.

24. The method of claim 23, further comprising indicating to a user how to move the external charger relative to the implantable medical device based on the determined alignment.

25. The method of claim 23, wherein the plurality of position determination coils comprises a first pair of coils and a second pair of coils, wherein the strength of the reflected magnetic fields at the first pair of coils determines alignment with respect to a first direction, and wherein the strength of the reflected magnetic fields at the second pair of coils determines alignment with respect to a second direction.

26. The method of claim 23, wherein at least two of the plurality of position determination coils are driven by a different current or voltage source.

27. The method of claim 23, wherein at least two of the plurality of position determination coils are driven by a same current or voltage source.

28. The method of claim 23, wherein the strength of the reflected magnetic fields is determined by measuring a voltage across each of the position determination coils.

29. The method of claim 28, wherein the voltage measurement is taken at an output of a voltage divider.

30. The method of claim 23, wherein the strength of the reflected magnetic fields is determined by simultaneous measurement of voltage across each of the plurality of position determination coils.