SWITCHED PROTECTIVE DEVICE AGAINST ELECTROMAGNETIC INTERFERENCE

• US 20110152972A1
• Filed: 12/16/2010
• Published: 06/23/2011
• Est. Priority Date: 12/22/2009
• Status: Active Grant

• Current Assignee: Biotronik SE & Company KG
• Original Assignee: Biotronik VI Patent AG (Biotronik SE & Company KG)
• Inventors: Weiss, Ingo, DOERR, Thomas
• Granted Patent: US 8,423,133 B2
• Time in Patent Office: Days
• US Class Current: 607/62
• 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: A61N 1/3925 Monitoring; Protecting

Abstract

A device and a method for working in the presence of electromagnetic fields, in particular fields occurring in magnetic resonance tomography (referred to below as “MRT” or “MRI”) imaging devices. More precisely, the invention relates to a medical device (MD) in which an electrode is in contact with bodily tissue, and for detection of electromagnetic interference fields the input characteristic of the MD is automatically modified by a switching device in such a way that the influences of the electromagnetic interference fields are minimized.

Claims

1. A medical device comprising

a unit configured to detect electromagnetic interference, having at least one sensor and/or indicator for electromagnetic interference fields;

at least one switching device coupled with said unit configured to detect electromagnetic interference;

at least one electrode coupled with said at least one switching device;

at least one control unit the unit coupled with the at least one electrode wherein said at least one control unit is further coupled with said unit configured to detect electromagnetic interference; and

,

wherein the at least one electrode is in contact with bodily tissue which enables detection of electromagnetic interference fields by said unit configured to detect electromagnetic interference and wherein an input characteristic of the at least one electrode is automatically modified via said at least one switching device in such a way that influences of the electromagnetic interference fields to said medical device are minimized.

2. The medical device according to claim 1, wherein the medical device is an implantable medical device.

3. The medical device according to claim 1, wherein the at least one switching device has a linear or nonlinear characteristic curve.

4. The medical device according to claim 1, wherein the at least one switching device is switched in series with one or more electromagnetic interference capacitors, or the at least one switching device is switched in parallel with an existing electromagnetic interference capacitor circuit.

5. The medical device according to claim 1, wherein the input characteristic may be modified with components having voltage-dependent capacitance.

6. The medical device according to claim 4, wherein the at least one switching device is configured so that the electromagnetic interference capacitors are reversed in polarity using a frequency which may be modified and/or predetermined, and/or which is automatically matched to a measured field intensity parameters, wherein a polarity reversal is carried out only for specific field parameters detected by the unit configured to detect electromagnetic interference, or is carried out continuously.

7. The medical device according to claim 6, wherein polarity reversal frequencies of individual switching elements of the at least one switching device are different and/or time-invariant and/or time-variant.

8. The medical device according to claim 6, wherein a polarity reversal frequency is determined taking into account a polarity of a charge flowing through an electrode line coupled with said at least one electrode.

9. The medical device according to claim 1, wherein a switching element of the at least one switching device is a modifiable resistor, modifiable capacitor, semiconductor, or a combination thereof.

10. The medical device according to claim 1, wherein a switch of the at least one switching device or a change of a operating point on a characteristic curve is triggered electrically, optically, acoustically, magnetically, or thermally.

11. The medical device according to claim 1, wherein the at least one switching device functions based on a frequency and is configured as an LC series circuit, wherein a resonance of the LC series circuit is set to an interference frequency to be diverted.

12. The medical device according to claim 1, further comprising a communication unit configured to establish a unidirectional or bidirectional connection with an magnetic resonance imaging device.

13. The medical device according to claim 12, wherein the at least one switching device is configured:

to be triggered and/or have switching controlled by said magnetic resonance imaging device via the communications unit and/or,

have an operating point changed on a characteristic curve of the at least one switching device by said magnetic resonance imaging device via the communication unit.

14. The medical device according to claim 1, wherein the unit configured to detect electromagnetic interference includes at least one of the following sensors or indicators:

GMR sensor,

MagFET sensor,

Hall sensor,

electro-optical converter,

battery voltage sensor configured to monitor voltage during capacitor charging,

RF field detector,

magnetic gradient field detector,

current detector for currents induced by electromagnetic fields,

vibration detector, for detection of vibrations induced by Lorentz forces.

15. The medical device according to claim 1, wherein in case of detection of electromagnetic interference fields and in addition to a modification to said input characteristic, said medical device is configured to:

change to an magnetic resonance imaging safe state,

remain for a prolonged period of time in an magnetic resonance imaging safe state or a state that is insensitive to electromagnetic interference fields,

synchronize electrical measurements with field intensity minimum values that occur with periodic or pulsed electromagnetic fields, or synchronize a stimulation with said field intensity minimum values, and

emit electromagnetic pulses to signal that the implantable medical device is present in an electromagnetic field, and to further signal to a magnetic resonance imaging device and transmit information regarding interference for display on a magnetic resonance imaging screen.