Implantable medical device with one or more magnetic field sensors to assist with external charger alignment

• US 9,339,660 B2
• Filed: 09/30/2014
• Issued: 05/17/2016
• Est. Priority Date: 10/04/2013
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Feldman, Emanuel, Parramon, Jordi, Ozawa, Robert D.
• Primary Examiner(s): Porter, Jr., Allen
• Application Number:
  US14/502,659
• Publication Number:
  US 20150100109A1
• Time in Patent Office: 595 Days
• Field of Search: 607/60, 607/61
• US Class Current: 1/1
• CPC Class Codes: A61N 1/37223 Circuits for electromagnetic coupling
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

An implantable medical device (IMD) is disclosed having one or more magnetic field sensors for measuring a strength of a magnetic charging field provided by an external charger and used to provide operational power to the IMD, for example, to charge its battery. The measured field strength data, or derivations of such data, are telemetered to the external charger, which further process the received data if necessary and can inform a user whether alignment between the external charger and IMD is sufficient, a misalignment direction, and/or a misalignment distance, so that the user can attempt to improve the alignment of the external charger. The one or more sensors are preferably placed at or equidistantly around a center axis of the IMD'"'"'s charging coil. However, the sensors may be placed at any number of locations in the IPG, and at different distances from the center axis.

Claims

1. An implantable medical device, comprising:

a coil configured to receive a magnetic charging field from an external charger, wherein the coil comprises a center axis;

a plurality of magnetic field sensors each configured to measure a strength of the magnetic charging field, wherein one of the plurality of magnetic field sensors is located at the center axis of the coil and wherein others of the plurality of the magnetic field sensors are located equidistant to the center axis;

telemetry circuitry configured to transmit alignment data to the external charger, wherein the alignment data is indicative of external charger alignment with respect to the implantable medical device, and wherein the alignment data comprises or is derived from the measured strengths; and

charging circuitry configured to use the received magnetic charging field to provide operational power to the implantable medical device.

2. The device of claim 1, wherein the magnetic field sensors are oriented to measure the strength of the magnetic charging field in a direction parallel to an axis of the coil.

3. The device of claim 1, wherein the magnetic field sensors comprise a coil.

4. The device of claim 1, wherein the magnetic field sensors comprise Hall sensors or giant magnetoresistance sensors.

5. The device of claim 1, further comprising a circuit board, wherein the magnetic field sensors are affixed to the circuit board.

6. The device of claim 1, further comprising an integrated circuit, wherein the magnetic field sensors are integrated with the integrated circuit or a package of the integrated circuit.

7. The device of claim 6, wherein the integrated circuit comprises the telemetry circuitry and the charging circuitry.

8. The device of claim 6, wherein the integrated circuit comprises stimulation circuitry configured to generate therapeutic currents at at least one electrode of the implantable medical device.

9. The device of claim 1, further comprising a case for housing the coil, the telemetry circuitry, and the charging circuitry.

10. The device of claim 9, wherein the magnetic field sensors are affixed to an inside or outside of the case.

11. The device of claim 1, further comprising a rechargeable battery, wherein the charging circuitry is configured to use the received magnetic charging field to provide operational power to the implantable medical device by charging the battery.

12. The device of claim 1, wherein the alignment data comprises an indication whether or not the external charger is sufficiently aligned with the implantable medical device.

13. The device of claim 1, wherein the alignment data comprises a comparison of the measured strengths to at least one threshold.

14. The device of claim 1, wherein the alignment data comprises a direction with which the external charger is misaligned with respect to the implantable medical device, or a distance with which the external charger is misaligned with respect to the implantable medical device, or both.

15. The device of claim 1, wherein the alignment data comprises an x/y offset with which the external charger is misaligned with respect to the implantable medical device.

16. The device of claim 1, wherein the telemetry circuitry is configured to transmit the alignment data to the external charger by modulating an impedance of the coil during receipt of the magnetic charging field.

17. The device of claim 1, wherein the telemetry circuitry is configured to transmit the alignment data to the external charger via a link separate from the magnetic charging field.

18. The device of claim 1, further comprising a battery, wherein the telemetry circuitry is further configured to transmit to the external charger one or more of a temperature of the implantable medical device, a charging current for the battery, or a voltage of the battery.

19. The device of claim 1, further comprising a memory comprising sensor offset data indicative of a location of each of the one or more plurality of magnetic field sensors in or on the implantable medical device.

20. The device of claim 19, further comprising control circuitry configured to derive the alignment data from the measured strengths and the sensor offset data.

21. The device of claim 19, wherein the at least one location is relative to a center axis of the coil.

22. The device of claim 19, wherein the sensor offset data comprises a strength each of the magnetic field sensors would expect to measure if the external charger was ideally aligned with the implantable medical device.

23. The device of claim 19, wherein the sensor offset data comprises a strength each of the magnetic field sensors would expect to measure if the external charger was misaligned with respect to the implantable medical device at a plurality of x/y offsets.

24. The device of claim 19, wherein the sensor offset data comprises data indicating a strength of the magnetic charging field as a function of radius.