Premium
Ultrafast volumetric B 1 + mapping for improved radiofrequency shimming in 3 tesla body MRI
Author(s) -
Sprinkart Alois M.,
Nehrke Kay,
Träber Frank,
Block Wolfgang,
Gieseke Jürgen,
Schmitz Georg,
Willinek Winfried A.,
Schild Hans,
Börnert Peter
Publication year - 2014
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.24438
Subject(s) - shim (computing) , flip angle , coronal plane , nuclear medicine , radio frequency , imaging phantom , materials science , physics , biomedical engineering , nuclear magnetic resonance , magnetic resonance imaging , computer science , medicine , radiology , surgery , telecommunications , erectile dysfunction
Purpose To evaluate the use of the recently proposed ultrafast B 1 + mapping approach DREAM (Dual Refocusing Echo Acquisition Mode) for a refinement of patient adaptive radiofrequency (RF) shimming. Materials and Methods Volumetric DREAM B 1 + 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 B 1 + 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. Results By 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 B 1 + cv (MS‐RF shim versus CS‐RF) were up to 14%/39%/47% in transversal slices/coronal slices/ spine area. Conclusion Volumetric information about B 1 + can be used to further improve the accuracy and homogeneity of the B 1 + field yielding higher diagnostic confidence, and will also be of value for various quantitative methods which are sensitive to flip angle imperfections. J. Magn. Reson. Imaging 2014;40:857–863 . © 2013 Wiley Periodicals, Inc .