• Alois M Sprinkart, Kay Nehrke, Frank Träber, Wolfgang Block, Jürgen Gieseke, Georg Schmitz, Winfried A Willinek, Hans Schild, and Peter Börnert.
• Department of Radiology, University of Bonn, Germany; Institute of Medical Engineering, Ruhr-University Bochum, Germany.
• J Magn Reson Imaging. 2014 Oct 1; 40 (4): 857-63.

PurposeTo evaluate the use of the recently proposed ultrafast B1 (+) mapping approach DREAM (Dual Refocusing Echo Acquisition Mode) for a refinement of patient adaptive radiofrequency (RF) shimming.Materials And MethodsVolumetric DREAM B1 (+) calibration scans centered in the upper abdomen were acquired in 20 patients and three volunteers with written informed consent at a clinical dual source 3 Tesla (T) MR system. Based on these data, RF transmit settings were optimized by central-slice based RF-shimming (CS-RF shim) and by a refined, multi-slice adaptive approach (MS-RF shim). Simulations were performed to compare flip angle accuracy and B1 (+) homogeneity (cv = stddev/mean) achieved by CS-RF shim versus MS-RF shim for transversal and coronal slices, and for volume shimming on the spine.ResultsBy MS-RF shim, mean deviation from nominal flip angle was reduced to less than 11% in all slices, all targets, and all subjects. Relative improvements in B1 (+) cv (MS-RF shim versus CS-RF) were up to 14%/39%/47% in transversal slices/coronal slices/ spine area.ConclusionVolumetric information about B1 (+) can be used to further improve the accuracy and homogeneity of the B1 (+) field yielding higher diagnostic confidence, and will also be of value for various quantitative methods which are sensitive to flip angle imperfections.© 2013 Wiley Periodicals, Inc.

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