MRI Compatible Implantable Medical Devices and Methods

• US 20080221638A1
• Filed: 03/09/2007
• Published: 09/11/2008
• Est. Priority Date: 03/09/2007
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Lloyd, Thomas W., Wedan, Steve R., Bobgan, Jean M.
• Granted Patent: US 9,345,888 B2
• Time in Patent Office: Days
• US Class Current: 607/34
• 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 29/0814 Field measurements related to measuring influence on or from apparatus, components or humans EMC, EMI and similar testing in general G01R31/001, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning
• 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 33/286 involving passive visualization of interventional instruments, i.e. making the instrument visible as part of the normal MR process

Abstract

An implantable medical device configured to be compatible with the environment inside an MRI machine. The implantable medical device includes a housing constructed of an electrically conductive material and pulse generation circuitry within the housing for generating electrical voltage pulses. The implantable medical device further includes a first conductor that is configured to transmit the electrical voltage pulses from the pulse generation circuitry to a patient'"'"'s cardiac tissue and a second conductor that is configured to provide an electrically conductive path from the patient'"'"'s cardiac tissue back to the pulse generation circuitry. The implantable medical device further includes a selectively interruptible electrically conductive path connecting the pulse generation circuitry with the housing.

Claims

1. An implantable medical device comprising:

a housing comprising an electrically conductive material;

pulse generation circuitry disposed within the housing for generating electrical voltage pulses;

a diode disposed in series with and between the housing and the pulse generation circuitry; and

a switch disposed in series with the diode, the switch configured to selectively isolate the housing from the pulse generation circuitry.

2. The implantable medical device of claim 1, the switch comprising a transistor.

3. The implantable medical device of claim 1, the switch comprising a relay.

4. The implantable medical device of claim 1, further comprising a magnetic field sensor.

5. The implantable medical device of claim 4, further comprising control circuitry that is configured to open the switch when the magnetic field sensor detects a magnetic field characteristic of magnetic resonance imaging.

6. The implantable medical device of claim 1, further comprising an induced current sensor that senses low frequency induced current in the implantable medical device.

7. The implantable medical device of claim 6, the induced current sensor disposed in series with the housing and the pulse generation circuitry.

8. The implantable medical device of claim 6, further comprising control circuitry that is configured to open the switch when the induced current sensor detects an electrical current that is characteristic of magnetic resonance imaging.

9. The implantable medical device of claim 1, further comprising:

a receiver configured to receive a first signal transmitted from outside of the patient'"'"'s body to the implanted medical device, and

control circuitry configured to open the switch in response to the first signal.

10. The implantable medical device of claim 1, further comprising:

a receiver configured to receive a second signal transmitted from outside of the patient'"'"'s body to the implanted medical device, and

control circuitry configured to close the switch in response to the second signal.

11. An implantable medical device comprising:

a housing constructed of an electrically conductive material;

pulse generation circuitry within the housing for generating electrical voltage pulses;

a first conductor configured to transmit the electrical voltage pulses from the pulse generation circuitry to a patient'"'"'s cardiac tissue;

a second conductor configured to provide an electrically conductive path from the patient'"'"'s cardiac tissue back to the pulse generation circuitry;

a first switch configured to selectively provide a first electrically conductive path connecting the second conductor and the pulse generation circuitry; and

a selectively interruptible second electrically conductive path connecting the pulse generation circuitry with the housing, the second electrically conductive path comprising a diode.

12. The implantable medical device of claim 11, where the second electrically conductive path comprises a second switch.

13. The implantable medical device of claim 12, where the second switch comprises a transistor.

14. The implantable medical device of claim 12, where the second switch comprises a relay.

15. The implantable medical device of claim 11, further comprising a magnetic field sensor.

16. The implantable medical device of claim 15, further comprising control circuitry that is configured to interrupt the selectively interruptible second electrically conductive path when the magnetic field sensor detects a magnetic field characteristic of magnetic resonance imaging.

17. An implantable medical device comprising:

a housing comprising an electrically conductive material;

pulse generation circuitry disposed within the housing for generating electrical voltage pulses;

a diode disposed in series with and between the housing and the pulse generation circuitry; and

a resistor disposed in series with and between the housing and the pulse generation circuitry.

18. The implantable medical device of claim 17, wherein the resistor has a resistance of 10,000 to 30,000 ohms.

19. The implantable medical device of claim 17, wherein the resistor has a resistance of 1,000 to 300,000 ohms.

20. An implantable medical device comprising:

a housing comprising an electrically conductive material; and

pulse generation circuitry disposed within the housing for generating electrical voltage pulses, wherein the pulse generation circuitry is configured to be electrically isolated from the housing at all times.