Medical implantable system for reducing magnetic resonance effects

• US 20030140931A1
• Filed: 01/29/2002
• Published: 07/31/2003
• Est. Priority Date: 01/29/2002
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Hrdlicka, Gregory A., Reinke, James D., Zeijlemaker, Volkert A., Cho, Yong Kyun, Foerster, Laurie D., Kalin, Ron
• Granted Patent: US 7,050,855 B2
• Time in Patent Office: Days
• US Class Current: 128/899
• CPC Class Codes: A61B 2090/0418 Compensation
• CPC Class Codes: A61B 2090/0481 against EM radiation, e.g. microwave
• CPC Class Codes: A61B 2090/3954 magnetic, e.g. NMR or MRI
• CPC Class Codes: A61B 90/04 Protection of tissue around surgical sites against effects of non-mechanical surgery, e.g. laser surgery protection of eyes against laser radiation A61F9/022
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

Apparatus and methods are disclosed for reducing the potentially harmful effects of electromagnetic waves on an implantable medical device. In one embodiment of the present invention, an implantable medical system comprising a dual threshold magnetic sensor capable of detecting an elevated magnetic field is disclosed. The sensor can comprise a solid-state sensor capable of detecting a static magnetic field in excess of about 1500 Gauss. The magnetic sensor can be operatively coupled to electronics that are capable of altering the operation of the system upon detection of an elevated magnetic field by the magnetic sensor.

Claims

1. An implantable medical system, comprising:

a magnetic sensor to detect a change in magnetic field surrounding the environment in which the system is located;

at least one circuit coupled to the sensor, wherein operation of the at least one circuit may be controlled based on magnetic field strength measurements obtained by the magnetic sensor.

2. The system of claim 1, wherein the magnetic sensor comprises a solid-state dual threshold sensor.

3. The system of claim 2, wherein the magnetic sensor is based on a Hall effect sensor.

4. The system of claim 1, wherein the magnetic sensor is capable of detecting a static magnetic field in excess of about 1500 Gauss.

5. The system of claim 1, wherein the at least one circuit includes a processing circuit to execute programmed instructions that control operations of the system in response to a change in magnetic field strength.

6. The system of claim 5, wherein ones of the programmed instructions executed by the processing circuit are determined based on magnetic field strength measurements obtained by the magnetic sensor.

7. The system of claim 5, wherein the magnetic sensor is capable of detecting multiple ranges of magnetic field strengths to control the operations of the system.

8. The system of claim 1, wherein the at least one circuit includes at least one additional sensor, and operation of the at least one additional sensor is controlled based on magnetic field strength measurements obtained by the magnetic sensor.

9. The system of claim 1, wherein the at least one circuit includes a communication circuit, and operation of the communication circuit is controlled based on magnetic field strength measurements obtained by the magnetic sensor.

10. The system of claim 1, wherein the at least one circuit includes at least one switch, and a state of the switch is determined based on magnetic field strength measurements obtained by the magnetic sensor.

11. The system of claim 1, and further including at least one electrical lead coupled to the at least one circuit, operation of the at least one electrical lead is controlled based on magnetic field strength measurements obtained by the magnetic sensor.

12. The system of claim 11, wherein the at least one circuit includes a circuit to reduce an electrical current flow within the at least one electrical lead upon detection of an elevated magnetic field by the magnetic sensor.

13. The system of claim 1, wherein the at least one circuit includes means for operating in a standard mode when magnetic field strength measurements obtained by the magnetic sensor are within a predetermined range.

14. The system of claim 13, wherein the predetermined range includes any magnetic field strength measurement below a predetermined minimum magnetic field strength.

15. The system of claim 14, wherein the minimum magnetic field strength is approximately 1500 Gauss.

16. The system of claim 11, wherein the at least one electrical lead is coupled to a filter.

17. The system of claim 16, wherein the filter includes a circuit to attenuate flow of current having a frequency within a predetermined frequency range.

18. An implantable medical system, comprising:

a magnetic sensor capable of detecting a magnetic field strength; and

electronics operatively coupled to the magnetic sensor capable of altering the operation of the system based on the magnetic field strength.

19. The system of claim 18, at further comprising at least one electrical lead operatively coupled to the electronics.

20. The system of claim 19, wherein the electronics includes a circuit capable of reducing electrical current flow within the at least one electrical lead upon detection of a magnetic field strength within a predetermined elevated magnetic field strength range.

21. The system of claim 20, wherein the electronics includes a circuit to resume normal operations of the system upon detecting a magnetic field strength below a predetermined elevated magnetic field strength range.

22. An implantable medical system, comprising:

electronics capable of monitoring and controlling the operation of the implantable medical system;

at least one electrical lead operatively coupled to the electronics; and

at least one filter operatively coupled to the at least one electrical lead capable of attenuating a signal within the at least one electrical lead.

23. The system of claim 22, wherein the at least one filter is capable of providing a low impedance path from the at least one electrical lead to a terminal of a power supply.

24. The system of claim 23, wherein the at least one filter is capable of providing a low impedance path from the at least one electrical lead to a terminal of a power supply upon the increase of voltage on the at least one electrical lead.

25. The system of claim 24, further comprising:

a magnetic sensor capable of detecting an elevated magnetic field.

26. The system of claim 25, wherein the electronics are capable of altering the operation of the system upon detection of an elevated magnetic field by the magnetic sensor.

27. A method of operating an implantable medical system, comprising:

a.) sensing a magnetic field having a field strength within a predetermined range; and

b.) altering the operation of the system to account for the sensed magnetic field having a field strength within the predetermined range.

28. The method of claim 27, wherein the system includes an electrical lead, and step b.) includes limiting electrical current flow within the electrical lead.

29. The method of claim 27, wherein the predetermined range includes a field strength of about 1500 Gauss or greater.

30. The method of claim 27, and further comprising:

detecting a magnetic field having a magnetic field strength outside of the predetermined range; and

resuming normal operations of the system.

31. The method of claim 27, wherein the system includes a sensor, and step b.) includes modifying use of the sensor within the system.

32. The method of claim 27, wherein the system includes a communication circuit, and step b.) includes modifying use of the communication circuit within the system.

33. The method of claim 27, wherein the system includes a processing circuit, and step b.) includes controlling execution of programmed instructions by the processing circuit based on the sensed magnetic field.

34. The method of claim 27, wherein the system includes at least one switch, and step b.) includes controlling a state of the switch based on the sensed magnetic field.