Ingmar Graesslin1, Christian Steiding1,
Bjoern Annighoefer2, Julia Weller1, Sven Biederer3,
David Brunner4, Hanno Homann1, Ferdinand Schweser5,
Ulrich Katscher1, Klaas Pruessmann4, Peter Boernert1
1Philips Research Europe, Hamburg,
Germany; 2TU Hamburg-Harburg, Hamburg, Germany; 3Institute
of Medical Engineering, University of Lbeck, Lbeck, Germany; 4University
and ETH Zurich, Zurich, Switzerland; 5IDIR / University Clinics,
Jena, Germany
With
increasing field strength the local specific absorption rate (SAR) becomes a
limiting factor for many MR imaging applications. Minimal SAR RF pulses can
be selected from the large solution space due to the extra degrees of freedom
in the RF pulse design. This paper extends the recently proposed temporal
averaging approach for local SAR reduction with multiple local SAR
constraints. It successively applies multiple RF pulses with similar target
excitation patterns, but different spatial SAR distributions, for averaging
out local hotspots. The concept was validated by simulations and initial
experiments on an 8-channel TX MRI system.
Keywords