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Cardiac gating using scattering of an 8‐channel parallel transmit coil at 7T
Author(s) -
Jaeschke Sven H.F.,
Robson Matthew D.,
Hess Aaron T.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27038
Subject(s) - scattering , shim (computing) , physics , signal (programming language) , optics , materials science , acoustics , nuclear magnetic resonance , computer science , medicine , erectile dysfunction , programming language
Purpose To establish a cardiac signal from scattering matrix or scattering coefficient measurements made on a 7T 8‐channel parallel transmit (pTx) system, and to evaluate its use for cardiac gating. Methods Measurements of the scattering matrix and scattering coefficients were acquired using a monitoring pulse sequence and during a standard cine acquisition, respectively. Postprocessing used an independent component analysis and gating feature identification. The effect of the phase of the excitation radiofrequency (RF) field ( B 1 +shim) on the cardiac signal was simulated for multipleB 1 +shim configurations, and cine images were reconstructed from both the scattering coefficients and electrocardiogram (ECG). Results The cardiac motion signal was successfully identified in all subjects with a mean signal‐to‐noise ratio of 33.1 and 5.7 using the scattering matrix and scattering coefficient measurements, respectively. The dominant gating feature in the cardiac signal was a peak aligned with end‐systole that occurred on average at 311 and 391 ms after the ECG trigger, with a mean standard deviation of 13.4 and 18.1 ms relative to ECG when using the scattering matrix and scattering coefficients measurements, respectively. The scattering coefficients showed a dependence onB 1 +shim with some shim configurations not showing any cardiac signal. Cine images were successfully reconstructed using the scattering coefficients with minimal differences compared to those using ECG. Conclusion We have shown that the scattering of a pTx RF coil can be used to estimate a cardiac signal, and that scattering matrix and coefficients can be used to cardiac gate MRI acquisitions with the scattering matrix providing a superior cardiac signal. Magn Reson Med 80:633–640, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.