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

• US 20110004278A1
• Filed: 07/06/2009
• Published: 01/06/2011
• Est. Priority Date: 07/06/2009
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Freidin, Lev, Chen, Joey, Aghassian, Daniel
• Granted Patent: US 8,473,066 B2
• Time in Patent Office: Days
• US Class Current: 607/61
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/0045 concerning the insertion or the connection of the batteries

Abstract

By incorporating magnetic field sensing coils in an external charger, it is possible to determine the position of an implantable device by sensing the reflected magnetic field from the implant. In one embodiment, two or more field sensing coils are arranged to sense the reflected magnetic field. By comparing the relative reflected magnetic field strengths of the sensing coils, 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 use with an implantable medical device, comprising:

a primary coil for producing a magnetic field for providing power to an implantable medical device;

a plurality of sensing coils; and

an alignment sensing circuit for determining an alignment of the primary coil relative to the implantable medical device, wherein the determination is based on electrical measurements taken from the plurality of sensing coils.

2. The external charger of claim 1, further comprising:

a position indication circuit coupled to the alignment sensing circuit for indicating to a user a misalignment of the external charger relative to the implantable medical device.

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

4. The external charger of claim 2, wherein the indication circuit activates 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 2, wherein the position indication circuit transmits misalignment information to another external device.

7. The external charger of claim 6, wherein the another external device indicates how the external charger should be moved to improve the alignment of the external charger relative to the implantable medical device.

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

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

10. The external charger of claim 1, wherein the plurality of sensing coils are located within a center of the primary coil.

11. The external charger of claim 1, wherein the primary coil is wound around a central axis, and wherein the plurality of sensing coils are wound around axes that are parallel to the central axis.

12. The external charger of claim 1, wherein the primary coil is wound around a central axis, and wherein the plurality of sensing coils are wound around second axes, and wherein the second axes are perpendicular to the central axis.

13. The external charger of claim 1, wherein the plurality of sensing coils comprises at least one pair of sensing coils, wherein the coils in each pair straddle a central axis of the primary coil.

14. The external charger of claim 13, wherein the coils in each pair are wound around axes that are parallel to the central axis of the primary coil.

15. The external charger of claim 13, wherein the coils in each pair are wound around axes that are perpendicular to the central axis of the primary coil.

16. The external charger of claim 13, wherein the coils in each pair are connected to each other.

17. The external charger of claim 16, wherein the coils in each pair are connected in series and end-to-end.

18. The external charger of claim 13, wherein the coils in each pair are not connected to each other.

19. The external charger of claim 13, comprising two pairs of sensing coils positioned orthogonally with respect to each other.

20. The external charger of claim 13, comprising three sensing coils positioned triangularly with respect to the central axis of the primary coil.

21. A method for assessing the alignment between an external charger and an implantable medical device, comprising:

producing from the external charger a magnetic field for providing power to an implantable medical device;

sensing reflections of the magnetic field from the implanted medical device at a plurality of sensing coils of 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 plurality of sensing coils.

22. The method of claim 21, 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.

23. The method of claim 22, wherein the another external device comprises an external device for controlling the therapeutic settings of the implantable medical device.

24. The method of claim 21, 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 21, wherein the plurality of sensing coils comprises a first pair of coils and a second pair of coils, wherein the first pair of coils indicate alignment with respect to a first direction, and wherein the second pair of coils indicate alignment with respect to a second direction perpendicular to the first direction.

26. The method of claim 23, wherein determining an alignment comprises:

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

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

27. The method of claim 23, wherein the coils in each pair are connected to each other, and wherein determining an alignment comprises:

measuring a first voltage across the first pair of coils and measuring a second voltage across the second pair of coils, and

producing a first error indication with respect to the first direction using the first voltage, and producing a second error indication with respect to the second direction using the second voltage.

28. The method of claim 21, wherein determining an alignment comprises using the electrical measurements to derive a first indicator and a second indicator, wherein the first and second indicators indicate misalignment with respect to first and second directions.