Magnetic resonance imaging interference immune device

• US 7,671,594 B2
• Filed: 04/05/2007
• Issued: 03/02/2010
• Est. Priority Date: 06/24/2003
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Gray, Robert W.
• Primary Examiner(s): Shrivastav; Brij B
• Application Number:
  US11/697,254
• Publication Number:
  US 20080079429A1
• Time in Patent Office: 1,062 Days
• Field of Search: 324300-322, 600407-445, 607/9
• US Class Current: 324/318
• 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: H01F 5/00 Coils superconducting coils H01F6/06; fixed inductances of the signal type H01F17/00
• CPC Class Codes: H03H 1/0007 of radio frequency interference filters

Abstract

A medical apparatus includes a medical assist device to process signals to relating biological functions. A first lead is operatively connected to the medical assist device, the first lead having a distal end and a proximal end. A second lead is operatively connected to the medical assist device, the second lead having a distal end and a proximal end. The first electrode is operatively connected to the distal end of the first lead, and a second electrode is operatively connected to the distal end of the second lead. A filter circuit is operatively connected near the distal end of the first lead and the distal end of the second lead. A compensation circuit, operatively connected to the first lead, provides a compensation voltage to enable the filter to effectively block changing magnetic fields induced current in the second lead from passing through the second electrode of the distal end of the second lead.

Claims

1. A medical apparatus, comprising:

a medical assist device to process signals to relating biological functions;

a first lead operatively connected to said medical assist device, said first lead having a distal end and a proximal end;

a second lead operatively connected to said medical assist device, said second lead having a distal end and a proximal end;

a first electrode operatively connected to said distal end of said first lead;

a second electrode operatively connected to said distal end of said second lead;

a filter circuit operatively connected near said distal end of said first lead and said distal end of said second lead; and

a compensation circuit, operatively connected to said first lead, to provide a compensation voltage to enable said filter to effectively block changing magnetic fields induced current in said second lead from passing through said second electrode of said distal end of said second lead.

2. The medical apparatus as claimed in claim 1, wherein said compensation circuit comprises:

a sensing circuit to sense voltages induced in said first lead, the voltages being induced by changing magnetic fields; and

a voltage compensation circuit, operatively connected to said sensing circuit and responsive thereto, to provide said compensation voltage.

3. The medical apparatus as claimed in claim 2, wherein said compensation circuit comprises:

a second sensing circuit to detect the changing magnetic fields;

said compensation circuit, operatively connected to said second sensing circuit and responsive thereto, to synchronize application of said compensation voltage with the sensed changing magnetic fields.

4. The medical apparatus as claimed in claim 1, wherein said compensation circuit comprises:

a sensing circuit to detect the changing magnetic fields;

said compensation circuit, operatively connected to said sensing circuit and responsive thereto, to synchronize application of said compensation voltage with the sensed changing magnetic fields.

5. The medical apparatus as claimed in claim 1, wherein said compensation circuit is located said proximal end of said first lead.

6. The medical apparatus as claimed in claim 1, wherein said compensation circuit is located within said medical assist device.

7. A medical apparatus, comprising:

a medical assist device to process signals to relating biological functions;

a first lead operatively connected to said medical assist device, said first lead having a distal end and a proximal end;

a second lead operatively connected to said medical assist device, said second lead having a distal end and a proximal end;

a first electrode operatively connected to said distal end of said first lead;

a second electrode operatively connected to said distal end of said second lead;

a filter circuit operatively connected near said distal end of said first lead and said distal end of said second lead; and

a compensation circuit including a coil that generates a voltage due to a changing MRI electromagnetic field, operatively connected to said first lead, to provide a compensation voltage to enable said filter to effectively block changing magnetic fields induced current in said second lead from passing through said second electrode of said distal end of said second lead.

8. The medical apparatus as claimed in claim 7, wherein said coil is curved in three different spatial directions.

9. The medical apparatus as claimed in claim 7, wherein said compensation circuit further comprises:

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

10. The medical apparatus as claimed in claim 7 wherein said compensation circuit comprises:

a plurality of coils, each coil generating a voltage due to a changing MRI electromagnetic field such that a combination of voltages due to a changing MRI electromagnetic field are produced.

11. The medical apparatus as claimed in claim 7 wherein said compensation circuit comprises:

three planar coils, each coil generating a voltage due to a changing MRI electromagnetic field such that a combination of voltages due to a changing MRI electromagnetic field are produced.

12. The medical apparatus as claimed in claim 7 wherein said compensation circuit comprises:

a plurality of coils, each coil generating a voltage due to a changing MRI electromagnetic field;

a sensor to measure a strength of voltages induced 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 voltages induced by the changing MRI electromagnetic field such that a combination of voltages due to a changing MRI electromagnetic field are produced.

13. The medical apparatus as claimed in claim 7 wherein said compensation circuit comprises:

three planar coils, each coil generating a voltage due to a changing MRI electromagnetic field;

a sensor to measure a strength of voltages induced 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 voltages induced by the changing MRI electromagnetic field such that a combination of voltages due to a changing MRI electromagnetic field are produced.

14. The medical apparatus as claimed in claim 7 wherein said compensation circuit comprises:

a plurality of coils, each coil generating a voltage due to a 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 voltages due to a changing MRI electromagnetic field.

15. The medical apparatus as claimed in claim 7 wherein said compensation circuit comprises:

three planar coils, each coil generating a voltage due to a 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 voltages due to a changing MRI electromagnetic field.

16. A medical apparatus, comprising:

a medical assist device to process signals to relating biological functions;

a first lead operatively connected to said medical assist device, said first lead having a distal end and a proximal end;

a second lead operatively connected to said medical assist device, said second lead having a distal end and a proximal end;

a first electrode operatively connected to said distal end of said first lead;

a second electrode operatively connected to said distal end of said second lead;

a first filter circuit operatively connected near said distal end of said first lead;

a second filter circuit operatively connected near said distal end of said second lead; and

a compensation circuit, operatively connected to said first filter and said second filter, to provide a compensation voltage to enable said first and second filters to effectively block changing magnetic fields induced current in said first and second leads from passing through said first and second electrodes of said distal ends of said first and second leads.

17. The medical apparatus as claimed in claim 16, wherein said first and second filters are capacitors.

18. The medical apparatus as claimed in claim 16, wherein said compensation circuit comprises:

a sensing circuit to detect the changing magnetic fields;

said compensation circuit, operatively connected to said sensing circuit and responsive thereto, to synchronize application of said compensation voltage with the sensed changing magnetic fields.

19. A medical apparatus, comprising:

a medical assist device to process signals to relating biological functions;

a first lead operatively connected to said medical assist device, said first lead having a distal end and a proximal end;

a second lead operatively connected to said medical assist device, said second lead having a distal end and a proximal end;

a first electrode operatively connected to said distal end of said first lead;

a second electrode operatively connected to said distal end of said second lead;

a first filter circuit operatively connected near said distal end of said first lead;

a second filter circuit operatively connected near said distal end of said second lead;

a third filter circuit operatively connected near said proximal end of said first lead;

a fourth filter circuit operatively connected near said proximal end of said second lead; and

a compensation circuit, operatively connected to said first filter and said second filter, to provide a compensation voltage to enable said first and second filters to effectively block changing magnetic fields induced current in said first and second leads from passing through said first and second electrodes of said distal ends of said first and second leads.

20. The medical apparatus as claimed in claim 19, wherein compensation circuit is operatively connected to said third filter and said fourth filter, to provide a compensation voltage to enable said third and fourth filters to effectively block changing magnetic fields induced current in said first and second leads from passing into said medical assist device.