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. MATERIALS AND 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.
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. MATERIALS AND 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: Gerrit Schultz; Peter Ullmann; Heinrich Lehr; Anna M Welz; Jürgen Hennig; Maxim Zaitsev Journal: Magn Reson Med Date: 2010-09-16 Impact factor: 4.668
Authors: Daniel Gallichan; Chris A Cocosco; Andrew Dewdney; Gerrit Schultz; Anna Welz; Jürgen Hennig; Maxim Zaitsev Journal: Magn Reson Med Date: 2010-11-30 Impact factor: 4.668
Authors: Jason P Stockmann; Clarissa Z Cooley; Bastien Guerin; Matthew S Rosen; Lawrence L Wald Journal: J Magn Reson Date: 2016-04-08 Impact factor: 2.229
Authors: Jonathan B Martin; Sai Abitha Srinivas; Christopher E Vaughn; Heng Sun; Mark A Griswold; William A Grissom Journal: Magn Reson Med Date: 2022-04-25 Impact factor: 3.737