title: Simultaneous mapping of water shift and B1(WASABI)-Application to field-Inhomogeneity correction of CEST MRI data.
abstract: Together with the development of MRI contrasts that are inherently small in their magnitude, increased magnetic field accuracy is also required. Hence, mapping of the static magnetic field (B0) and the excitation field (B1) is not only important to feedback shim algorithms, but also for postprocess contrast-correction procedures.
  
  
  
  A novel field-inhomogeneity mapping method is presented that allows simultaneous mapping of the water shift and B1(WASABI) using an off-resonant rectangular preparation pulse. The induced Rabi oscillations lead to a sinc-like spectrum in the frequency-offset dimension and allow for determination of B0by its symmetry axis and of B1by its oscillation frequency.
  
  
  
  Stability of the WASABI method with regard to the influences of T1, T2, magnetization transfer, and repetition time was investigated and its convergence interval was verified. B0and B1maps obtained simultaneously by means of WASABI in the human brain at 3 T and 7 T can compete well with maps obtained by standard methods. Finally, the method was applied successfully for B0and B1correction of chemical exchange saturation transfer MRI (CEST-MRI) data of the human brain.
  
  
  
  The proposed WASABI method yields a novel simultaneous B0and B1mapping within 1 min that is robust and easy to implement. Magn Reson Med 77:571-580, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors: German Cancer Research Center (DKFZ), Medical Physics in Radiology, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.
authors: Patrick
authors: P
authors: Schuenke
authors: German Cancer Research Center (DKFZ), Medical Physics in Radiology, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.
authors: Johannes
authors: J
authors: Windschuh
authors: Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Am Fassberg 11, D-37077, Göttingen, Germany.
authors: Volkert
authors: V
authors: Roeloffs
authors: German Cancer Research Center (DKFZ), Medical Physics in Radiology, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.
authors: Mark E
authors: ME
authors: Ladd
authors: German Cancer Research Center (DKFZ), Medical Physics in Radiology, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.
authors: Peter
authors: P
authors: Bachert
authors: German Cancer Research Center (DKFZ), Medical Physics in Radiology, Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany.
authors: Moritz
authors: M
authors: Zaiss
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001834:Body Water / Q000378:metabolism*; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D057054:Molecular Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
keywords: B0 mapping; B1 mapping; CEST; WASABI; field mapping