Adapted RF pulse design for SAR reduction in parallel excitation with  experimental verification at 9.4 T.
Parallel excitation holds strong promises to mitigate the impact of large transmit B1 (B+1) distortion at very high magnetic field. Accelerated RF pulses, however, inherently tend to require larger values in RF peak power which may result in substantial increase in Specific Absorption Rate (SAR) in tissues, which is a constant concern for patient safety at very high field. In this study, we demonstrate adapted rate RF pulse design allowing for SAR reduction while preserving excitation target accuracy. Compared with other proposed implementations of adapted rate RF pulses, our approach is compatible with any k-space trajectories, does not require an analytical expression of the gradient waveform and can be used for large flip angle excitation. We demonstrate our method with numerical simulations based on electromagnetic modeling and we include an experimental verification of transmit pattern accuracy on an 8 transmit channel 9.4 T system.
Wu
Xiaoping
X
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
Akgün
Can
C
Vaughan
J Thomas
JT
Andersen
Peter
P
Strupp
John
J
Uğurbil
Kâmil
K
Van de Moortele
Pierre-François
PF
D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology; D003198:Computer Simulation; D004574:Electromagnetic Fields; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D011846:Radio Waves