TY - JOUR
T1 - Cardiac imaging at 7 tesla
T2 - Single- and two-spoke radiofrequency pulse design with 16-channel parallel excitation
AU - Schmitter, Sebastian
AU - Delabarre, Lance
AU - Wu, Xiaoping
AU - Greiser, Andreas
AU - Wang, Dingxin
AU - Auerbach, Edward J.
AU - Vaughan, J. Thomas
AU - Uǧurbil, Kâmil
AU - Van De Moortele, Pierre François
PY - 2013/11
Y1 - 2013/11
N2 - Purpose Higher signal to noise ratio (SNR) and improved contrast have been demonstrated at ultra-high magnetic fields (≥7 Tesla [T]) in multiple targets, often with multi-channel transmit methods to address the deleterious impact on tissue contrast due to spatial variations in B1+ profiles. When imaging the heart at 7T, however, respiratory and cardiac motion, as well as B0 inhomogeneity, greatly increase the methodological challenge. In this study we compare two-spoke parallel transmit (pTX) RF pulses with static B1+ shimming in cardiac imaging at 7T. Methods Using a 16-channel pTX system, slice-selective two-spoke pTX pulses and static B1+ shimming were applied in cardiac CINE imaging. B1+ and B0 mapping required modified cardiac triggered sequences. Excitation homogeneity and RF energy were compared in different imaging orientations. Results Two-spoke pulses provide higher excitation homogeneity than B1+ shimming, especially in the more challenging posterior region of the heart. The peak value of channel-wise RF energy was reduced, allowing for a higher flip angle, hence increased tissue contrast. Image quality with two-spoke excitation proved to be stable throughout the entire cardiac cycle. Conclusion Two-spoke pTX excitation has been successfully demonstrated in the human heart at 7T, with improved image quality and reduced RF pulse energy when compared with B1 + shimming. Magn Reson Med 70:1210-1219, 2013. © 2013 Wiley Periodicals, Inc.
AB - Purpose Higher signal to noise ratio (SNR) and improved contrast have been demonstrated at ultra-high magnetic fields (≥7 Tesla [T]) in multiple targets, often with multi-channel transmit methods to address the deleterious impact on tissue contrast due to spatial variations in B1+ profiles. When imaging the heart at 7T, however, respiratory and cardiac motion, as well as B0 inhomogeneity, greatly increase the methodological challenge. In this study we compare two-spoke parallel transmit (pTX) RF pulses with static B1+ shimming in cardiac imaging at 7T. Methods Using a 16-channel pTX system, slice-selective two-spoke pTX pulses and static B1+ shimming were applied in cardiac CINE imaging. B1+ and B0 mapping required modified cardiac triggered sequences. Excitation homogeneity and RF energy were compared in different imaging orientations. Results Two-spoke pulses provide higher excitation homogeneity than B1+ shimming, especially in the more challenging posterior region of the heart. The peak value of channel-wise RF energy was reduced, allowing for a higher flip angle, hence increased tissue contrast. Image quality with two-spoke excitation proved to be stable throughout the entire cardiac cycle. Conclusion Two-spoke pTX excitation has been successfully demonstrated in the human heart at 7T, with improved image quality and reduced RF pulse energy when compared with B1 + shimming. Magn Reson Med 70:1210-1219, 2013. © 2013 Wiley Periodicals, Inc.
KW - 7T
KW - RF pulse design
KW - cardiac CINE imaging
KW - pTX
KW - parallel transmission
KW - spoke excitation
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U2 - 10.1002/mrm.24935
DO - 10.1002/mrm.24935
M3 - Article
C2 - 24038314
AN - SCOPUS:84886800142
SN - 0740-3194
VL - 70
SP - 1210
EP - 1219
JO - Magnetic resonance in medicine
JF - Magnetic resonance in medicine
IS - 5
ER -