MRI-Compatible Cardiac Defibrillator for RF Image Noise Control

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Solution Overview

Problem

Current cardiac defibrillators are not compatible with MRI environments, leading to delays in administering defibrillation during MRI procedures, which can increase mortality risks and cause patient injury or damage to the MRI scanner due to radiofrequency interference and muscle contractions.

Innovation Solution

A cardiac defibrillator system with a low pass filter and RF traps to prevent radiofrequency interference, allowing immediate defibrillation within the MRI bore, and a waveform to condition skeletal muscle for reduced contraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If a cardiac defibrillator is used during MRI procedures, then immediate defibrillation can be administered, but radiofrequency interference causes noise in MRI images and potential damage to the scanner

Engineering Contradiction:

Improvetime to administer defibrillationVSAvoidradiofrequency interference

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

A low pass filter is introduced as an intermediary component between the defibrillator and the MRI system. The filter has a cutoff frequency below the MRI Larmor frequency, allowing it to block radiofrequency interference from reaching the MRI scanner while permitting defibrillation signals to pass through, thus resolving the contradiction between immediate defibrillation and preventing RF interference

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The defibrillator's inherent radiofrequency emissions, which were previously harmful causing image noise and scanner interference, are converted into a beneficial signal by using the low pass filter to selectively block only the harmful high-frequency components while allowing the therapeutic defibrillation pulse to pass through unchanged

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Loss of time

If a cardiac defibrillator is used during MRI procedures, then immediate defibrillation can be administered, but skeletal muscle contractions cause patient injury and scanner damage

Engineering Contradiction:

Improvetime to administer defibrillationVSAvoidskeletal muscle contraction

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

A waveform conditioning circuit is implemented that pre-modifies the defibrillation waveform before delivery to the patient. The circuit conditions the electrical waveform to reduce the intensity and duration of skeletal muscle stimulation, thereby preventing violent muscle contractions and associated injuries while maintaining the therapeutic defibrillation effect on the heart

Inventive Principle:

Principle #10Preliminary action

3Reliability

If radiofrequency traps are added to block MRI signals, then patient and scanner are protected, but device complexity increases

Engineering Contradiction:

Improveprotection from MRI radiofrequency signalsVSAvoiddefibrillator system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Radiofrequency traps with specific resonant frequencies are incorporated into the defibrillator system. These traps are tuned to resonate at the MRI Larmor frequency, creating a narrowband filter that selectively blocks MRI radiofrequency signals while having minimal impact on the broader defibrillation waveform, thus providing protection without significantly increasing system complexity

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables safe and immediate defibrillation within the MRI scanner without compromising imaging performance, reducing patient injury and scanner damage, and ensuring regulatory approval through unmodified generator functionality.

Implementation Method 1

a low pass filter electrically connected between the defibrillator generator and the first and second electric wires to prevent noise in an MRI image caused by radiofrequency interference from the defibrillator, as well as protect a patient and the defibrillator from MRI radiofrequency imaging signals

Methodology Applied

Scientific EffectLow pass filtering: Filter (electronic)

Implementation Method 2

first and second electric wires, each being electrically connected to the defibrillator generator; first and second defibrillation pads, each being electrically connected to a respective one of the first and second electric wires

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS20250281762A1MRI-compatible cardiac defribrillator

Publication Date: 2025.09.11 JOHNS HOPKINS UNIVERSITY

AI summary

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.