title: Spatial phase encoding exploiting the Bloch-Siegert shift effect.
abstract: OBJECTIVE
  The present work introduces an alternative to the conventional B0-gradient spatial phase encoding technique. By applying far off-resonant radiofrequency (RF) pulses, a spatially dependent phase shift is introduced to the on-resonant transverse magnetization. This so-called Bloch-Siegert (BS) phase shift has been recently used for B1(+)-mapping. The current work presents the theoretical background for the BS spatial encoding technique (BS-SET) using RF-gradients.
  
  
  METHODS
  Since the BS-gradient leads to nonlinear encoding, an adapted reconstruction method was developed to obtain undistorted images. To replace conventional phase encoding gradients, BS-SET was implemented in a two-dimensional (2D) spin echo sequence on a 0.5 T portable MR scanner.
  
  
  RESULTS
  A 2D spin echo (SE) measurement imaged along a single dimension using the BS-SET was compared to a conventional SE 2D measurement. The proposed reconstruction method yielded undistorted images.
  
  
  CONCLUSIONS
  BS-gradients were demonstrated as a feasible option for spatial phase encoding. Furthermore, undistorted BS-SET images could be obtained using the proposed reconstruction method.
authors.affiliation: Department of Experimental Physics 5, University of Würzburg, Am Hubland, 97074, Würzburg, Germany, ralf.kartaeusch@physik.uni-wuerzburg.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kartäusch
authors.forename: Toni
authors.initials: T
authors.lastname: Driessle
authors.forename: Thomas
authors.initials: T
authors.lastname: Kampf
authors.forename: Thomas Christian
authors.initials: TC
authors.lastname: Basse-Lüsebrink
authors.forename: Uvo Christoph
authors.initials: UC
authors.lastname: Hoelscher
authors.forename: Peter Michael
authors.initials: PM
authors.lastname: Jakob
authors.forename: Florian
authors.initials: F
authors.lastname: Fidler
authors.forename: Xavier
authors.initials: X
authors.lastname: Helluy
mesh_terms: D000465:Algorithms; D004867:Equipment Design; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D018547:Plant Stems; D011846:Radio Waves