Abstract #3145
Overcoming the SAR limitation of magnetization transfer pulses at 7 Tesla using parallel transmission
Bastien Guerin 1 , Jonathan R Polimeni 1 , Thomas Witzel 1 , and Lawrence L Wald 1,2
1
Department of Radiology, Massachusetts
General Hospital, Charlestown, MA, United States,
2
Division
of Health Sciences Technology, Harvard-MIT, MA, United
States
Magnetization transfer (MT) pulses are useful for
background reduction in time-of-flight angiography but
are difficult to deploy at high fields because of their
high specific absorption rate (SAR). We design MT pulses
at 7 Tesla with improved saturation performance by
control of SAR using parallel transmission (pTx). A
first performance improvement is obtained by
constraining local SAR in the pulse design using the
virtual observation point concept. Saturation
performance at constant SAR is further improved by
irradiating multiple frequencies simultaneously. Indeed,
as in Simultaneous Multi-Slice, this allows the design
algorithm to better control local SAR using SAR
hopping between frequencies.
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