Laminated magnet keeper for implant device

• US 6,178,353 B1
• Filed: 07/14/1999
• Issued: 01/23/2001
• Est. Priority Date: 07/27/1998
• Status: Expired due to Term

• Current Assignee: Advanced Bionics AG (Sonova Holding AG)
• Original Assignee: Advanced Bionics Corporation (Sonova Holding AG)
• Inventors: Malmgren, Richard P., Griffith, Glen A.
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US09/353,236
• Time in Patent Office: 559 Days
• Field of Search: 607/33, 607/61, 607/57, 607/55, 607/56
• US Class Current: 607/61
• CPC Class Codes: A61N 1/36038 Cochlear stimulation
• CPC Class Codes: A61N 1/37223 Circuits for electromagnetic coupling
• CPC Class Codes: A61N 1/37276 characterised by means for reducing power consumption during telemetry
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

An implantable medical device, such as an implantable cochlear stimulator (ICS) system, utilizes laminated, sectionalized or particle-ized permanent magnets and/or keepers in both the implant portion and external (non-implanted) portion so as to reduce the electrical energy absorbed by both the implant device and the external device when in use. In one embodiment, the implant device employs a sectionalized, laminated or particle-based “keeper”, while the external device employs a sectionalized, laminated or particle-ized magnet, making the implant device immune to being damaged by MRI (magnetic resonance imaging). The combination of the sectionalized/laminated/particle magnets and the sectionalized/laminated/particle keepers creates a very high electrical resistance path across the boundaries of the laminations, sections, or particles, thereby reducing the magnitude of eddy currents that would otherwise flow transversely through the keeper in the presence of a magnetic flux passing through the keeper or magnet. The reduction of eddy currents, in turn, reduces energy loss.

Claims

1. An implantable medical device comprising:

a receiving coil adapted to be electromagnetically coupled with a transmitting coil of an external device;

a magnetic element responsive to a magnetic field for holding the implantable medical device in a desired position that aligns the receiving coil with the transmitting coil for efficient power and signal transfer between the receiving and transmitting coils;

means for reducing energy loss within the magnetic element as power and signal transfers occur between the receiving and transmitting coils;

whereby the implantable medical device operates with less loss relative to the amount of energy coupled into the receiving coil.

2. The implantable medical device of claim 1 wherein the magnetic element comprises a permanent magnet, and wherein the means for reducing energy loss within the permanent magnet comprises magnetic sections joined together with a dielectric (electrical insulative) material.

3. The implantable medical device of claim 1 wherein the magnetic element comprises a magnetic keeper made from a magnetic material that reduces magnetic reluctance.

4. The implantable medical device of claim 3 wherein the means for reducing energy loss within the magnetic keeper comprises discrete sections of the magnetic keeper joined together with a dielectric (electrical insulative) glue or cement, whereby the magnetic keeper comprises a sectionalized magnetic keeper.

5. The implantable medical device of claim 3 wherein the means for reducing energy loss within the magnetic keeper comprises laminations of the magnetic material joined together with a dielectric (electrical insulative) glue or cement, whereby the magnetic keeper comprises a laminated magnetic keeper.

6. The implantable medical device of claim 3 wherein the means for reducing energy loss within the magnetic keeper comprises making the magnetic material from magnetic particles sintered with a dielectric material between the particles.

7. The implantable medical device of claim 3 wherein the magnetic material from which the magnetic keeper is made is selected from the group of magnetic materials comprising:

silicon steel, Hiperco Alloy 50, and Accucore.

8. An improved implantable medical device having a receiving coil adapted to be coupled with an external magnetic field for providing power and control signals to the implantable medical device, and further including a magnetic element that helps align the receiving coil with the external magnetic field in order to make the transfer of power and control signals more efficient, wherein the improvement comprises a magnetic element having laminations, sections or particles that minimize the formation of eddy currents in the magnetic element in the presence of a magnetic field.

9. The improved implantable medical device of claim 8 wherein the medical device comprises an implantable cochlear stimulator (ICS), and further wherein the magnetic element comprises a magnetic keeper made from a material that provides a low magnetic reluctance path for magnetic flux, but which does not become permanently magnetized in the presence of a strong externally-generated magnetic field, such as one produced by a magnetic resonance imaging (MRI) system.

10. The improved implantable medical device of claim 9 wherein the magnetic material from which the magnetic keeper is made is selected from the group of magnetic materials comprising:

silicon steel, Hiperco Alloy 50, and Accucore.

11. A medical device system comprising a first part and a second (non-implanted) part, the first part and the second part each having a coil therein through which power may be inductively coupled from the first part to the second part when the respective coils are aligned, comprising:

a first magnetic element in the first part;

a second magnetic element in the second part adapted to be magnetically attracted to the first magnetic element in the first part, which attraction aligns the respective coils for efficient power and signal transfer;

wherein at least the second magnetic element has electrical resistance blocking means therein for minimizing the formation of eddy currents in the second magnetic element when in the presence of a magnetic field, thereby making the transfer of power into the second part more efficient.

12. The medical device system of claim 11 wherein the second magnetic element comprises a sectionalized magnetic keeper made from discrete sections of a magnetic material that provides a low reluctance path for the magnetic field, wherein the discrete sections are bonded together with a dielectric material exhibiting a high electrical resistance.

13. The medical device system of claim 11 wherein the second magnetic element comprises a laminated magnetic keeper made from discrete layers of a magnetic material that provides a low reluctance path for the magnetic field, wherein the discrete layers are held together with a dielectric material exhibiting a high electrical resistance.

14. The medical device system of claim 11 wherein the second magnetic element comprises electrically-isolated magnetic particles.

15. The medical device system of claim 14 wherein the second magnetic element comprises a sintered magnetic keeper made from magnetic particles sintered with a dielectric material between the particles, wherein the particles provide a low reluctance path for the magnetic field, and wherein the dielectric material exhibits a high electrical resistance.

16. A method for reducing power losses associated with the transfer of energy into an implantable medical device from an external device via inductive coupling, the implantable medical device having a first magnetic element therein adapted to be magnetically attracted to a second (non-implanted) magnetic element, comprising:

positioning the first magnetic element relative to an implanted coil within the implantable medical device so that when the first magnetic element is maximally magnetically attracted to the second magnetic element, the implanted coil is aligned with an external coil for efficient inductive coupling; and

configuring the first (implanted) magnetic element so as to minimize the formation of eddy currents therein when the second magnetic element is in the presence of a magnetic field.

17. The method of claim 16 wherein configuring the first magnetic element to minimize eddy current formation comprises sectionalizing the first (implanted) magnetic element by separating the magnetic element into discrete sections and bonding the sections together with a dielectric material.

18. The method of claim 16 wherein configuring the first magnetic element to minimize eddy current formation comprises laminating the first (implanted) magnetic element by forming the element from discrete layers and bonding the layers together with a dielectric material.

19. The method of claim 16 wherein configuring the first magnetic element to minimize eddy current formation comprises sintering the first (implanted) magnetic element by forming the element from discrete magnetic particles and sintering a dielectric material between the particles.

20. The method of claim 16 further including configuring the second (non-implanted) magnetic element so as to minimize the formation of eddy currents therein when the second magnetic element is in the presence of a magnetic field.