Magnetic resonance imaging interference immune device

• US 7,742,825 B2
• Filed: 08/29/2007
• Issued: 06/22/2010
• Est. Priority Date: 06/24/2003
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Gray, Robert W., MacDonald, Stuart G.
• Primary Examiner(s): Manuel; George
• Assistant Examiner(s): Wieland; Robert N
• Application Number:
  US11/846,558
• Publication Number:
  US 20080058913A1
• Time in Patent Office: 1,028 Days
• Field of Search: 600/13, 600/422, 600/423, 600/424, 600/373, 600/420, 607/116, 607/122, 607/2, 607/9, 607/27, 343/893
• US Class Current: 607/116
• CPC Class Codes: A61B 2562/222 Electrical cables or leads therefor, e.g. coaxial cables or ribbon cables
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/086 Magnetic resonance imaging [MRI] compatible leads
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: G01R 33/285 Invasive instruments, e.g. catheters or biopsy needles, specially adapted for tracking, guiding or visualization by NMR
• CPC Class Codes: G01R 33/288 Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room
• CPC Class Codes: G01R 33/34084 implantable coils or coils being geometrically adaptable to the sample, e.g. flexible coils or coils comprising mutually movable parts
• CPC Class Codes: H03H 7/42 Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns

Abstract

A voltage compensation unit reduces the effects of induced voltages upon a device having a single wire line. The single wire line has balanced characteristic impedance. The voltage compensation unit includes a tunable compensation circuit connected to the wire line. The tunable compensation circuit applies supplemental impedance to the wire line. The supplemental impedance causes the characteristic impedance of the wire line to become unbalanced, thereby reducing the effects of induced voltages caused by changing magnetic fields.

Claims

1. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

a coil having an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field opposite to that voltage induced by the changing MRI electromagnetic field in the electrical lead wherein the cancelling voltage reduces the voltage induced by the changing MRI electromagnetic field in the electrical lead.

2. The electrical lead as claimed in claim 1, wherein said coil is curved in three different spatial directions.

3. The electrical lead as claimed in claim 1, wherein said coil is a nonplanar loop.

4. The electrical lead as claimed in claim 1, wherein said coil is a planar loop.

5. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

a coil having an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field opposite to that voltage induced by the changing MRI electromagnetic field in the electrical lead wherein the cancelling voltage reduces the voltage induced by the changing MRI electromagnetic field in the electrical lead; and

orientation means for changing a spatial orientation of said coil to modify the strength of the cancelling voltage induced by the changing MRI electromagnetic field.

6. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

a plurality of selectable coils, at least one selected coil defining an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field opposite to a voltage induced by the changing MRI electromagnetic field in the electrical lead such that a combination of the cancelling voltage and the voltage due to a changing MRI electromagnetic field provides a combined voltage having a reduced magnitude to the voltage induced by the changing MRI electromagnetic field.

7. The electrical lead as claimed in claim 6, wherein said coils are orientated in different directions.

8. The electrical lead as claimed in claim 6, wherein said coils are nonplanar.

9. The electrical lead as claimed in claim 6, wherein two coils are orthogonally orientated.

10. The electrical lead as claimed in claim 6, wherein three coils are orthogonally orientated.

11. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

planar coils, at least one coil having an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field such that a combination of the cancelling voltage and a voltage due to a changing MRI electromagnetic field provides a combined voltage having a reduced magnitude to the voltage induced by the changing MRI electromagnetic field.

12. The electrical lead as claimed in claim 11, wherein said planar coils are orientated in different directions.

13. The electrical lead as claimed in claim 11, wherein two planar coils are orthogonally orientated.

14. The electrical lead as claimed in claim 11, wherein three planar coils are orthogonally orientated.

15. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

a plurality of coils, at least one coil having an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field;

a sensor to measure a strength of a voltage induced in the electrical lead by the changing MRI electromagnetic field; and

a switching device, operatively connected to said sensor and plurality of coils, to operatively connect a number of said plurality of coils in response to the measured strength of the voltage induced by the changing MRI electromagnetic field providing a combined voltage having a reduced magnitude to the voltage induced by the changing MRI electromagnetic field in the electrical lead.

16. The electrical lead as claimed in claim 15, wherein said coils are orientated in different directions.

17. The electrical lead as claimed in claim 15, wherein said coils are nonplanar.

18. The electrical lead as claimed in claim 15, wherein two coils are orthogonally orientated.

19. The electrical lead as claimed in claim 15, wherein three coils are orthogonally orientated.

20. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

planar coils, at least one coil having an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field;

a sensor to measure a strength of a voltage induced in the electrical lead by the changing MRI electromagnetic field; and

a switching device, operatively connected to said sensor and said coils, to operatively connect a number of said coils in response to the measured strength of the voltage induced by the changing MRI electromagnetic field providing a combined voltage having a reduced magnitude to the voltage induced by the changing MRI electromagnetic field in the electrical lead.

21. The electrical lead as claimed in claim 20, wherein said planar coils are orientated in different directions.

22. The electrical lead as claimed in claim 20, wherein two planar coils are orthogonally orientated.

23. The electrical lead as claimed in claim 20, wherein three planar coils are orthogonally orientated.

24. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

a plurality of coils, at least one coil having an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field;

a transceiver to receive a signal indicating a number of coils to be connected; and

a switching device, operatively connected to said transceiver and plurality of coils, to operatively connect a number of said plurality of coils in response to the received signal indicating the number of coils to be connected such that a combination of the cancelling voltage and a voltage induced in the electrical lead due to the changing MRI electromagnetic field provides a combined voltage having a reduced magnitude to the voltage induced by the changing MRI electromagnetic field in the electrical lead.

25. The electrical lead as claimed in claim 24, wherein said coils are orientated in different directions.

26. The electrical lead as claimed in claim 24, wherein said coils are nonplanar.

27. The electrical lead as claimed in claim 24, wherein two coils are orthogonally orientated.

28. The electrical lead as claimed in claim 24, wherein three coils are orthogonally orientated.

29. An electrical lead for a medical device, the electrical lead capable of providing an electrical path to a desired tissue region, comprising:

planar coils, at least one coil having an adjustable area to interact with a changing MRI electromagnetic field to generate a cancelling voltage due to the changing MRI electromagnetic field;

a transceiver to receive a signal indicating a number of coils to be connected; and

a switching device, operatively connected to said transceiver and said coils, to operatively connect a number of said coils in response to the received signal indicating the number of coils to be connected such that a combination of the cancelling voltage and a voltage induced in the electrical lead due to the changing MRI electromagnetic field provides a combined voltage having a reduced magnitude to the voltage induced by the changing MRI electromagnetic field in said electrical lead.

30. The electrical lead as claimed in claim 29, wherein said planar coils are orientated in different directions.

31. The electrical lead as claimed in claim 29, wherein two planar coils are orthogonally orientated.

32. The electrical lead as claimed in claim 29, wherein three planar coils are orthogonally orientated.