MRI-compatible cardiac defibrillator

Patent metadata

Field	Value
Publication number	US-11185707-B2
Application number	US-201716467373-A
Country	US
Kind code	B2
Filing date	Dec 8, 2017
Priority date	Dec 9, 2016
Publication date	Nov 30, 2021
Grant date	Nov 30, 2021

Abstract

A magnetic-resonance-imaging-compatible (MRI-compatible) cardiac defibrillator includes: a defibrillator generator; first and second electric wires, each being electrically connected to said defibrillator generator; first and second defibrillation pads, each being electrically connected to a respective one of said first and second electric wires; and a low pass filter electrically connected between said defibrillator generator and said first and second electric wires to prevent a noise in an MRI image caused by a radiofrequency interference from the defibrillator as well as protect a patient and the defibrillator from MRI radiofrequency imaging signals, wherein said low pass filter has a cutoff frequency set such that differential mode noise at an MRI Larmor frequency is in an attenuated band while a system-test signal by said defibrillator generator is in a pass band of said low pass filter.

First claim

We claim:

1. A magnetic-resonance-imaging-compatible (MRI-compatible) cardiac defibrillator, comprising:
a defibrillator generator comprising a plurality of stages of geometric multipliers followed by a plurality stages of voltage multipliers;
first and second electric wires, each being electrically connected to said defibrillator generator;
first and second defibrillation pads, each being electrically connected to a respective one of said first and second electric wires; and
a low pass filter electrically connected between said defibrillator generator and said first and second electric wires to prevent a noise in an MRI image caused by a radiofrequency interference from the defibrillator as well as protect a patient and the defibrillator from MRI radiofrequency imaging signals,
wherein said low pass filter has a cutoff frequency set such that differential mode noise at an MRI Larmor frequency is in an attenuated band while a system-test signal by said defibrillator generator is in a pass band of said low pass filter,
wherein said defibrillator generator is an MRI-compatible defibrillator generator that is substantially free of magnetic materials.

2. The MRI-compatible cardiac defibrillator according to claim 1 , wherein said low pass filter is at least a 7-pole low pass filter constructed to filter said differential mode noise at said MRI Larmor frequency by at least 80 dB.

3. The MRI-compatible cardiac defibrillator according to claim 1 , wherein said low pass filter is at least a 7-pole low pass filter constructed to filter said differential mode noise at said MRI Larmor frequency by at least 90 dB.

4. The MRI-compatible cardiac defibrillator according to claim 1 , wherein said first and second electric wires are formed into a twisted pair of wires.

5. The MRI-compatible cardiac defibrillator according to claim 1 , further comprising a plurality of radio-frequency (RF) traps tuned to said MRI Larmor frequency attached to said first and second electric wires spaced apart from each other in order to reduce common-mode emission from said defibrillator generator and to prevent patient-skin heating from RF-energy induced by an MRI scanner's body transmit coil.

6. The MRI-compatible cardiac defibrillator according to claim 1 , wherein said defibrillation pads are slotted defibrillation pads.

7. The MRI-compatible cardiac defibrillator according to claim 1 , wherein said MRI-compatible defibrillator generator comprises six stages of geometric multipliers followed by thirteen stages of voltage multipliers.

8. The MRI-compatible cardiac defibrillator according to claim 1 , wherein said defibrillator generator is configured to produce a muscle-conditioning signal immediately prior to a cardiac stimulating pulse so as to decrease a degree of rapid muscle contraction by a subject undergoing cardiac defibrillation.

9. The MRI-compatible cardiac defibrillator according to claim 1 , wherein said defibrillator generator is configured to apply a waveform to the patient just prior to delivery of a defibrillator shock.

10. The MRI-compatible cardiac defibrillator according to claim 9 , wherein the waveform is used to condition the skeletal muscle to reduce or avoid its violent contraction caused by the defibrillator shock.

11. A kit for converting a cardiac defibrillator to an MRI-compatible cardiac defibrillator, said cardiac defibrillator comprising a defibrillator generator, and said kit comprising:
a low pass filter structured to be electrically connected to said defibrillator generator between first and second electric wires of said MRI-compatible cardiac defibrillator to prevent a noise in an MRI image caused by a radiofrequency interference from the defibrillator as well as protect a patient and the defibrillator from MRI radiofrequency imaging signals,
wherein said low pass filter has a cutoff frequency between a pass and attenuated bands set such that differential mode noise at an MRI Larmor frequency is in said attenuated band while a signal by said defibrillator generator for system tests is in said pass band of said low pass filter,
wherein said defibrillator generator comprises a plurality of stages of geometric multipliers followed by a plurality stages of voltage multipliers,
wherein said defibrillator generator is an MRI-compatible defibrillator generator that is substantially free of magnetic materials.

12. The kit according to claim 11 , wherein said low pass filter is at least a 7-pole low pass filter constructed to filter said differential mode noise at said MRI Larmor frequency by at least 80 dB.

13. The kit according to claim 11 , wherein said low pass filter is at least a 7-pole low pass filter constructed to filter said differential mode noise at said MRI Larmor frequency by at least 90 dB.

14. The kit according to claim 11 , further comprising said first and second electric wires, said first and second electric wires being formed into a twisted pair of wires.

15. The kit according to claim 11 , further comprising a plurality of radio-frequency (RF) traps tuned to said MRI Larmor frequency attached to said first and second electric wires spaced apart from each other in order to reduce common-mode emission from said defibrillator generator and to prevent patient-skin heating from RF-energy induced by an MRI scanner's body transmit coil.

16. The kit according to claim 11 , further comprising slotted defibrillation pads.

Assignees

• Univ Johns Hopkins

Inventors

• Halperin Henry
• Schmidt Ehud J
• Watkins Ronald D
• Tandri Harikrishna
• Hunter David
• Tung Leslie
• Berger Ronald D

Classifications

• A61N1/3925 Primary

  Monitoring; Protecting · CPC title

• A61B5/361

  Detecting fibrillation · CPC title

• A61B5/055

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• A61N1/3904 Primary

  External heart defibrillators [EHD] · CPC title

• A61N1/39

  Heart defibrillators · CPC title