Wireless ECG Transceiver With RF Cancellation for MRI Gating
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Solution Overview
Problem
Current MRI systems face challenges in accurately detecting the ECG 'R' wave due to strong static magnetic fields, induced currents in conductive blood, moving magnetic gradients, and high-power pulsed RF fields, which distort signals and pose safety risks for patient leads.
Innovation Solution
A wireless transceiver system with a magnetic field tolerant amplifier, RF cancellation delay line, and flexible patient leads with distributed impedance, utilizing a 2.4 GHz RF transceiver for point-to-point communication to minimize interference and ensure accurate ECG signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional patient leads and cables are used to bring ECG signal out of the magnet bore, then the ECG signal can be transmitted to amplifiers, but artifacts are generated in the ECG signal due to moving magnetic gradients and RF fields
Solution Approach 1:
The patent extracts the ECG signal acquisition function from the traditional lead-cable-amplifier system and places it directly within the MRI bore at the patient's chest. The wireless transceiver captures the ECG signal locally, eliminating the need for leads and cables that generate artifacts when exposed to moving magnetic gradients and RF fields.
Solution Approach 2:
The patent replaces the mechanical electrical connection system (leads and cables) with a wireless electromagnetic transmission system. The ECG signal is transmitted wirelessly from the patient to the MRI system using RF communication, eliminating the physical conductors that would otherwise generate artifacts through electromagnetic induction in the time-varying magnetic fields.
2Productivity
If high-power pulsed RF fields are present in the MRI system, then imaging can be performed, but eddy currents are generated in patient leads causing heat and potential burns
Solution Approach 1:
The patent removes the patient leads from the system entirely by implementing wireless ECG signal acquisition. The wireless transceiver on the patient captures and transmits ECG signals without using conductive leads that would otherwise generate eddy currents and heat when exposed to the high-power pulsed RF fields used in MRI imaging.
Solution Approach 2:
The patent introduces an RF wireless communication intermediary to transmit the ECG signal from the patient to the MRI system. This intermediary uses electromagnetic waves in the RF range for communication, which are transparent to the MRI imaging RF pulses and do not generate harmful eddy currents or heat like conductive leads would.
3Object-affected harmful factors
If patient leads with distributed impedance are used to limit eddy currents, then safety is improved, but electrical noise in the system increases
Solution Approach 1:
The patent replaces the electrical lead-based signal transmission system with a wireless electromagnetic transmission system. This substitution eliminates the need for impedance-matched leads and avoids the electrical noise problems associated with high-impedance lead configurations in the MRI environment.
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
The system effectively cancels RF interference, reduces artifacts, and ensures safe and accurate ECG signal detection even in intense MRI environments, providing reliable cardiac gating for MRI and other imaging procedures.
Implementation Method 1
Each of the coils is non-inductively wound to cancel induced currents from a magnetic gradient
Implementation Method 2
The movement of blood in the magnetic field results in a 'magneto-homodynamic effect'; electrical currents induced in the blood
Implementation Method 3
a second problem is caused by the moving magnetic field gradients, since they will cause currents to be generated in any conductor exposed to them
Implementation Method 4
A wire, looped around on itself, will appear as a short circuit through the insulator. This in turn will allow for the generation of eddy currents in the loop, which will then heat the wire
Data Source
AI summary
A magnetic field tolerant amplifier having an amplifier stage, a differential to single-ended output amplifier stage and a first and second delay line. In another embodiment the invention relates to a magnetic gradient cancellation delay line including two coils connected in series at a junction and non-inductively wound to cancel induced currents from magnetic gradient. In another embodiment the invention relates to a patient lead including a flexible circuit substrate having a flexible conductor having distributed impedance. In still yet another embodiment the invention relates to a wireless transceiver system including an RF cancellation delay line; a differential amplifier stage; a differential to single ended output amplifier stage; an A/D converter; an RF transceiver and an antenna.