• Andreas Lesch, Matthias Schlöegl, Martin Holler, Kristian Bredies, and Rudolf Stollberger.
• Institute of Medical Engineering, Graz University of Technology, Graz, Austria.
• Magn Reson Med. 2019 Feb 1; 81 (2): 881-892.

PurposeHighly accelerated B http://www.w3.org/1998/Math/MathML"> 1 + -mapping based on the Bloch-Siegert shift to allow 3D acquisitions even within a brief period of a single breath-hold.Theory And MethodsThe B http://www.w3.org/1998/Math/MathML"> 1 + dependent Bloch-Siegert phase shift is measured within a highly subsampled 3D-volume and reconstructed using a two-step variational approach, exploiting the different spatial distribution of morphology and B http://www.w3.org/1998/Math/MathML"> 1 + -field. By appropriate variable substitution the basic non-convex optimization problem is transformed in a sequential solution of two convex optimization problems with a total generalized variation (TGV) regularization for the morphology part and a smoothness constraint for the B http://www.w3.org/1998/Math/MathML"> 1 + -field. The method is evaluated on 3D in vivo data with retro- and prospective subsampling. The reconstructed B http://www.w3.org/1998/Math/MathML"> 1 + -maps are compared to a zero-padded low resolution reconstruction and a fully sampled reference.ResultsThe reconstructed B http://www.w3.org/1998/Math/MathML"> 1 + -field maps are in high accordance to the reference for all measurements with a mean error below 1% and a maximum of about 4% for acceleration factors up to 100. The minimal error for different sampling patterns was achieved by sampling a dense region in k-space center with acquisition times of around 10-12 s for 3D-acquistions.ConclusionsThe proposed variational approach enables highly accelerated 3D acquisitions of Bloch-Siegert data and thus full liver coverage in a single breath hold.© 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

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