MRI Gradient-Induced Voltage Removal in ECG Monitoring
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Solution Overview
Problem
During magnetic resonance imaging (MRI) scans, large induced voltages from MRI gradient coils overlay electrocardiogram (ECG) signals, making it difficult to observe true ECG traces and restricts physiological monitoring and synchronization, especially for severely ill patients.
Innovation Solution
A method using gradient waveforms to estimate and remove induced voltages by fitting parameters to a physical model of gradient-induced voltages, allowing for the preservation of signal fidelity and accurate monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If strong low-pass filters are applied to remove high-frequency components of induced voltages, then the amplitude of induced voltages is reduced, but the ECG traces become temporally distorted and lose diagnostic fidelity
Solution Approach 1:
The patent uses the known gradient waveforms (which cause the harmful induced voltages) to model and predict the induced voltage components. By converting the harmful gradient-induced interference into a predictable signal that can be subtracted, the method removes the distortion caused by traditional filtering while preserving the true ECG signal fidelity
Solution Approach 2:
The patent introduces an intermediate physical model that relates gradient waveforms to induced voltages through fitting parameters. This model acts as a mediator between the known gradient signals and the corrupted ECG signals, enabling precise removal of induced voltage components without the signal degradation caused by direct filtering
2Object-affected harmful factors
If ECG electrodes are placed close together at the center of the bore to minimize induced voltage, then induced voltage amplitude is reduced, but the system complexity increases and diagnostic capability is limited
Solution Approach 1:
The patent replaces the mechanical/electrical solution of optimizing electrode placement with a signal processing solution. Instead of physically configuring electrodes to minimize induced voltages, the method uses computational modeling to subtract induced voltage components from any electrode configuration, thereby reducing system complexity while maintaining signal quality
3Object-affected harmful factors
If high impedance transmission lines are used to reduce current from gradient-induced voltages, then induced voltage amplitude is reduced, but signal fidelity is degraded and noise content increases
Solution Approach 1:
The patent transforms the harmful high-impedance effect into a beneficial measurement opportunity. By modeling the high-impedance transmission line behavior and incorporating it into the physical model, the method uses these lines to capture full-amplitude gradient-induced voltages for accurate modeling and subsequent removal, rather than treating them as mere attenuation elements
4Object-affected harmful factors
If adaptive digital filters are used to reduce ECG noise by detecting gradient waveforms, then induced voltage amplitude is reduced, but the system complexity increases and systematic derivation is lacking
Solution Approach 1:
The patent changes the approach from complex adaptive filtering to a parameter-based physical model. By identifying and estimating a small number of fitting parameters that characterize the relationship between gradient waveforms and induced voltages, the method achieves effective noise removal with significantly reduced system complexity and clear systematic derivation
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 the removal of gradient-induced voltages in real-time with minimal latency, maintaining the full diagnostic fidelity of ECG signals for effective physiological monitoring during MRI scans.
Implementation Method 1
large induced voltages are superimposed on the conventional ECG traces. These voltages arise as a result of the MRI gradient coils, which induce large electrical fields into the human body
Data Source
AI summary
Systems and methods for estimating time-dependent voltages that are induced in electrophysiological monitoring systems by magnetic field gradients generated during a magnetic resonance imaging (“MRI”) scan are provided. The gradient-induced voltages are subsequently removed from signals acquired with the electrophysiological monitoring system during an MRI scan. As an example, the electrophysiological monitoring system can include an electrocardiography (“ECG”) system, an electroencephalography (“EEG”) system, an electromyography (“EMG”) system, a voltage device tracking (“VDT”) system, and so on. The gradient-induced voltages are estimated using a two-step procedure in which a learning algorithm is used to determine fitting parameters to be used in a model of the gradient-induced voltages. The fitting parameters are then used together with the model to extract the gradient-induced voltages from signals acquired during an MRI scan. The gradient-induced voltages can then be removed from the acquired signals.