ECG Triggering in Ultra-High Field Cardiovascular MRI

Area of Science:

• Cardiovascular Imaging
• Magnetic Resonance Imaging
• Biomedical Engineering

Background:

• Ultra-high field (UHF) cardiac MRI (≥ 7 Tesla) offers enhanced resolution and tissue characterization capabilities.
• Electrocardiogram (ECG) triggering is crucial for cardiac MRI synchronization but is challenged by the magnetohydrodynamic (MHD) effect at UHF.
• The MHD effect, caused by blood flow in a magnetic field, induces voltages that distort ECG signals, particularly the R-wave, leading to triggering artifacts.

Purpose of the Study:

• To evaluate the performance of a conventional 3-lead ECG trigger device and a state-of-the-art algorithm for cardiac synchronization at 7 T.
• To demonstrate the feasibility of reliable ECG triggering in healthy subjects at 7 T without specialized equipment.
• To assess the accuracy of R-wave detection despite significant ECG signal distortions caused by the MHD effect.

Main Methods:

• Cardiac MRI was performed at 7 T in 8 healthy subjects.
• ECG signals and trigger events were recorded during imaging.
• A conventional 3-lead ECG trigger device and a state-of-the-art algorithm were employed.
• Subject preparation and an R-wave detection learning phase outside the magnetic field were utilized.

Main Results:

• Successful synchronized cardiac imaging was achieved at 7 T, despite severe ECG signal distortions.
• Analysis of recorded ECG signals, vectorcardiograms, and trigger event spacing indicated high accuracy in R-wave detection.
• The implemented method enabled reliable ECG triggering without additional hardware.

Conclusions:

• Accurate ECG triggering for ultra-high field cardiac MRI is feasible at 7 T using appropriate preparation and algorithms.
• The MHD effect can be overcome, allowing for artifact-free synchronized imaging.
• This approach facilitates advanced cardiac tissue characterization at UHF MRI.