External Charger for a Medical Implantable Device Using Field Inducing Coils to Improve Coupling

• US 20140012352A1
• Filed: 09/11/2013
• Published: 01/09/2014
• Est. Priority Date: 10/15/2009
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Aghassian, Daniel
• Granted Patent: US 9,044,617 B2
• Time in Patent Office: Days
• US Class Current: 607/61
• 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:

one or more current or voltage sources configured to provide a plurality of currents that produce a plurality of magnetic fields at different locations in the external charger; and

an alignment sensing circuit configured to determine an alignment of the external charger relative to the implantable medical device, wherein the determination is based on electrical measurements for each of the plurality of currents taken from the one or more current or voltage sources.

2. The external charger of claim 1, further comprising a position indication circuit configured to receive the determination and to indicate a misalignment of the external charger relative to the implantable medical device.

3. The external charger of claim 2, wherein the position indication circuit is further configured to indicate how to improve the alignment of the external charger relative to the implantable medical device.

4. The external charger of claim 2, wherein the position indication circuit is configured to activate visual indicators on the external charger.

5. The external charger of claim 4, 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.

6. The external charger of claim 1, wherein the electrical measurements are indicative of reflections of the magnetic fields from the implantable medical device.

7. The external charger of claim 1, wherein the one or more current or voltage sources comprise one or more current sources, and wherein the electrical measurements comprises voltages used by the one or more current sources to provide each of the plurality of currents.

8. The external charger of claim 1, wherein the one or more current or voltage sources comprise one or more voltage sources, and wherein the electrical measurements comprises the magnitude of the plurality of currents provided by the one or more voltage sources.

9. The external charger of claim 1, further comprising a primary coil, wherein the primary coil is configured to produce a primary coil magnetic field to provide power to the implantable medical device, wherein a central axis of the primary coil magnetic field and central axes of the plurality of magnetic fields are parallel.

10. The external charger of claim 9, wherein the primary coil magnetic field has a first frequency, the plurality of magnetic fields have second frequencies, and the first frequency is different from the second frequency.

11. The external charger of claim 9, wherein the central axes of the plurality of magnetic fields are equidistant from the central axis of the primary coil magnetic field at the different locations.

12. The external charger of claim 1, wherein the plurality of currents are provided to a plurality of coils at the locations.

13. The external charger of claim 1, comprising a plurality of current or voltage sources, each configured to provide one of the plurality of currents.

14. The external charger of claim 1, comprising a single current or voltage source for providing each of the plurality of currents.

15. A method for providing power to an implantable medical device using an external charger, comprising:

providing a first magnetic field from the external charger to provide power to the implantable medical device;

providing from one or more current or voltage sources a plurality of currents that produce a plurality of second magnetic fields at different locations in the external charger; and

determining an alignment of the external charger relative to the implantable medical device, wherein the determination is based on electrical measurements taken from the one or more current or voltage sources.

16. The method of claim 15, wherein determining the alignment comprises determining in which direction to move the external charger to improve the alignment of the external charger relative to the implantable medical device.

17. The method of claim 16, further comprising transmitting to another external device the determined direction.

18. The method of claim 17, wherein the another external device comprises an external device for controlling the therapeutic settings of the implantable medical device.

19. The method of claim 16, further comprising indicating the determined direction to a user.

20. The method of claim 15, wherein the locations occur in pairs, wherein the electrical measurements taken from the one or more current or voltage sources providing the currents to a first pair of locations indicate the alignment with respect to a first direction, and wherein the electrical measurements taken from the one or more current or voltage sources providing the currents to a second pair of locations indicate the alignment with respect to a second direction orthogonal to the first direction.

21. The method of claim 20, wherein the one or more current or voltage sources comprise one or more current sources, and wherein determining the alignment comprises:

comparing voltages used to provide the currents in the first pair to produce a first error indication with respect to the first direction, and

comparing voltages used to provide the currents in the second pair to produce a second error indication with respect to the second direction.

22. The method of claim 20, wherein the one or more current or voltage sources comprise one or more voltages sources, and wherein determining the alignment comprises:

comparing magnitudes of the currents in the first pair to produce a first error indication with respect to the first direction, and

comparing magnitudes of the currents in the second pair to produce a second error indication with respect to the second direction.

23. The method of claim 15, wherein the first magnetic field is provided by a primary coil in the external charger.

24. The method of claim 15, wherein the second magnetic fields are provided by coils at the different locations.

25. The method of claim 15, wherein the first magnetic field and the plurality of second magnetic fields have different frequencies.

26. The method of claim 15, wherein second central axes of the plurality of second magnetic fields are equidistant from a first central axis of the first magnetic field at the different locations.

27. The method of claim 15, wherein second central axes of the plurality of second magnetic fields and a first central axis of the first magnetic field are parallel.

28. The method of claim 15, wherein at least two of the plurality of currents are provided by different current or voltage sources.

29. The method of claim 15, wherein at least two of the plurality of currents are provided by the same current or voltage source.

30. The method of claim 15, wherein the electrical measurements comprises voltages used to produce the currents.

31. The method of claim 15, wherein the electrical measurements comprise magnitudes of the plurality of currents.

32. The method of claim 15, wherein the electrical measurements are taken simultaneously.

33. The method of claim 15, wherein the power provided to the implantable medical device is temporarily interrupted to take the electrical measurements.