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Updated: Apr 28, 2026
Registered Bioimaging of Nanomaterials for Diagnostic and Therapeutic Monitoring
Published on: December 9, 2010
Ultrafast volumetric B1 (+) mapping for improved radiofrequency shimming in 3 tesla body MRI
Alois M Sprinkart1, Kay Nehrke, Frank Träber
1Department of Radiology, University of Bonn, Germany; Institute of Medical Engineering, Ruhr-University Bochum, Germany.
Purpose:
To 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 Methods:
Volumetric 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.
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 B1 (+) cv (MS-RF shim versus CS-RF) were up to 14%/39%/47% in transversal slices/coronal slices/ spine area.
Conclusion:
Volumetric 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.
