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TOMOGRAPHY, September 2016, Volume 2, Issue 3: 167-174
DOI: 10.18383/j.tom.2016.00193

ECG Triggering in Ultra-High-Field Cardiovascular MRI

Daniel Stäb1,2, Juergen Roessler3, Kieran O’Brien4, Christian Hamilton-Craig5, Markus Barth1

1The Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia; 2Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany; 3Siemens Healthcare GmbH, Erlangen, Germany; 4Siemens Healthcare Pty Ltd, Brisbane, Australia; and 5Richard Slaughter Centre of Excellence in CVMRI, The Prince Charles Hospital, Brisbane, Queensland, Australia

Abstract

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.

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