Volume 18 Supplement 1

19th Annual SCMR Scientific Sessions

Open Access

ECG Electrode Placements for Magnetohydrodynamic Voltage Suppression and improving Cardiac Gating in high-field MRI

  • Thomas S Gregory1,
  • John Oshinski2,
  • Ehud J Schmidt3 and
  • Zion T Tse1
Journal of Cardiovascular Magnetic Resonance201618(Suppl 1):P328

https://doi.org/10.1186/1532-429X-18-S1-P328

Published: 27 January 2016

Background

The accuracy of Electrocardiogram (ECG) gating for synchronization of MR scanner image acquisition and cardiac electrical activity is of great importance for acquiring high-quality Cardiac Magnetic Resonance (CMR) images free of motion artefacts. The distortion of ECG traces by Magnetohydrodynamic Voltages (VMHD) induced by interaction between the MRI static magnetic field (B0) and rapid left-ventricular blood ejection during systole can lead to false and/or intermittent QRS complex detection and images with severe motion artefacts [1]. We hypothesized that an optimized electrode placement for the reduction of induced VMHD could be derived based on a thoracic model to increase the accuracy of QRS complex detection.

Methods

A vector model based on thoracic geometry [2] was calibrated using 12-lead ECGs recorded in four subjects in a GE 3T scanner to estimate VMHD distributions on the thorax. 4-lead ECG electrode placement was then optimized to: (1) minimize VMHD magnitude and (2) reduce displacement from the SA node for maximizing QRS complex amplitude (Figure 1a,b). A gradient-descent optimization routine was utilized to predict the optimal 4-lead ECG placement based on angular displacement and heart/aorta geometry (Figure 1c,d). Model results were then validated using five healthy subjects. Sensitivity (Se) and Positive Predictability (+P) rates for detection of R-waves were compared between conventional and MHD-suppressed lead placements for single-lead QRS complex detection [3].
Figure 1

Development of electrode placement recommendations for increased accuracy in QRS complex detection and MRI gating.

Results

A 43.41% reduction in VMHD during the S-T segment (Figure 1f) was observed in ECGs using the MHD-suppressed placement relative to the conventional placement, while preserving the QRS complex (Figure 1e), resulting in an average increase in the Se and +P rate of 14.22% and 15.48%, respectively (Figure 1e-g). Rpeak amplitude inside the MRI in the MHD-suppressed placement had <5% deviation from the standard placement outside of the MRI (Figure 1e). As compared to the conventional electrode placement (Figure 1c-d), MHD suppression may result from decreased visibility of the aorta through the lungs at the MHD-suppressed placement.

Conclusions

Electrode placement recommendations were computed and validated in a 3T MRI, illustrating an increased accuracy in QRS complex detection using the MHD-suppressed placement.

Authors’ Affiliations

(1)
College of Engineering, University of Georgia
(2)
Radiology, Emory University Hospital
(3)
Radiology, Brigham and Women's Hospital

References

  1. Gregory : MRM. 2014Google Scholar
  2. Oostendorp : IEEE. 2004Google Scholar
  3. Pan : IEEETransBiomed. 1985Google Scholar

Copyright

© Gregory et al. 2016

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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