Optimizing electrocardiograph electrode placement for cardiac-gated magnetic resonance imaging

Area of Science:

• Medical Imaging
• Cardiovascular Physiology
• Biomedical Engineering

Background:

• Magnetic resonance imaging (MRI) is crucial for cardiac imaging.
• Electrocardiographs (ECG) are used for cardiac-gating in MRI.
• Blood flow in MRI scanners induces electrical potentials that interfere with ECG signals.

Purpose of the Study:

• To determine which standard 12-lead ECG configuration minimizes blood flow-induced artifacts during MRI.
• To identify ECG leads that maximize the QRS complex amplitude for accurate cardiac-gating.
• To compare artifact interference and QRS signal strength across different ECG leads in a magnetic field.

Main Methods:

• 12-lead ECGs were recorded from healthy volunteers and patients both inside and outside a 1.5 Tesla MRI scanner.
• Artifact ECGs were generated by subtracting recordings taken outside the magnet from those taken inside.
• The amplitude of flow-induced potentials and QRS axes were measured and plotted in frontal and transverse planes.

Main Results:

• Superimposed potentials were largest in ECG leads I, II, V1, and V2, and smallest in leads III and AVF.
• A low-amplitude 7-10 Hz signal was present in most leads.
• While leads III and AVF had minimal superimposed potentials, leads V5, V6, or a left posterior chest lead offered the most consistent maximization of QRS and reduction of artifact.

Conclusions:

• Standard 12-lead ECGs are affected by blood flow potentials in MRI.
• Leads V5, V6, or a left posterior chest lead are recommended for cardiac-gating during MRI to minimize artifacts.
• A 7-10 Hz frequency filter may aid in artifact reduction for specific subjects.