A 1.5T MRI-conditional 12-lead electrocardiogram for MRI and intra-MR intervention

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Cardiovascular Technology

Background:

• High-fidelity 12-lead electrocardiograms (ECG) are crucial for patient monitoring during Magnetic Resonance Imaging (MRI) guided interventions and cardiac MRI.
• Acquiring uncorrupted ECG signals within MRI environments is challenging due to superimposed magneto-hydro-dynamic (MHD) voltage, gradient switching-induced voltages, and radiofrequency heating, which worsen with increasing magnetic field strength.
• Existing ECG systems often fail to provide reliable data in the MRI setting, limiting physiological monitoring capabilities.

Purpose of the Study:

• To develop and clinically validate a novel 1.5T MRI-conditional 12-lead ECG system.
• To overcome the technical challenges of obtaining high-fidelity ECG signals within a 1.5T MRI environment.
• To enable accurate physiological monitoring during MR-guided procedures and cardiac MRI.

Main Methods:

• The system was engineered using transmission lines to minimize radiofrequency induction and switching circuits to eliminate induced voltages.
• Adaptive filters were employed, trained with ECG data acquired both inside and outside the MRI scanner, to effectively remove MHD voltage.
• The system's performance was evaluated on 10 volunteers (including one exercising) and four patients with arrhythmias.

Main Results:

• The switching circuits successfully reduced imaging-induced voltages, with residual noise below 3% of the R-wave amplitude.
• MHD voltage removal resulted in intra-MRI ECGs that closely matched external recordings (variation <3.8%), preserving critical waveform segments.
• The system produced clear ECGs in premature ventricular contraction (PVC) patients, distinguishing between PVC and sinus rhythm beats, with measured heating below 1.5°C.
• The ECG system reliably supported multiphase cine scans and phase-contrast cine scans, even in subjects where traditional 4-lead gating failed.
• Robust ECG processing required a minimum repetition time of 4 ms.

Conclusions:

• High-fidelity intra-MRI 12-lead ECG acquisition is feasible.
• The developed 1.5T MRI-conditional ECG system effectively mitigates MRI-related artifacts.
• This technology enhances the potential for comprehensive physiological monitoring during cardiac MRI and interventions.