ECG Triggering in Ultra-High Field Cardiovascular MRI

• Published in: Tomography (Ann Arbor) Vol. 2; no. 3; pp. 167 - 174
• Main Authors: Stäb, Daniel, Roessler, Juergen, O'Brien, Kieran, Hamilton-Craig, Christian, Barth, Markus
• Format: Journal Article
• Language: English
• Published: United States Grapho Publications, LLC 01.09.2016
• Subjects: Advances in Brief; ECG; MRI; magnetohydrodynamic effect; ultra-high field; cardiac
• ISSN: 2379-139X; 2379-1381; 2379-139X
• DOI: 10.18383/j.tom.2016.00193

Cardiac magnetic resonance imaging at ultra-high field (B0 ≥ 7 T) potentially provides improved resolution and new opportunities for tissue characterization. Although an accurate synchronization of the acquisition to the cardiac cycle is essential, electrocardiogram (ECG) triggering at ultra-high field can be significantly impacted by the magnetohydrodynamic (MHD) effect. Blood flow within a static magnetic field induces a voltage, which superimposes the ECG and often affects the recognition of the R-wave. The MHD effect scales with B0 and is particularly pronounced at ultra-high field creating triggering-related image artifacts. Here, we investigated the performance of a conventional 3-lead ECG trigger device and a state-of-the-art trigger algorithm for cardiac ECG synchronization at 7 T. We show that by appropriate subject preparation and by including a learning phase for the R-wave detection outside of the magnetic field, reliable ECG triggering is feasible in healthy subjects at 7 T without additional equipment. Ultra-high field cardiac imaging was performed with the ECG signal and the trigger events recorded in 8 healthy subjects. Despite severe ECG signal distortions, synchronized imaging was successfully performed. Recorded ECG signals, vectorcardiograms, and large consistency in trigger event spacing indicate high accuracy for R-wave detection.