title: Probing signal phase in direct visualization of short transverse relaxation time component (ViSTa).
abstract: OBJECTIVE
  To demonstrate the phase evolutions of direct visualization of short transverse relaxation time component (ViSTa) matches with those of myelin water.
  
  
  METHODS
  Myelin water imaging (MWI) measures short transverse signals and has been suggested as a biomarker for myelin. Recently, a new approach, ViSTa, has been proposed to acquire short T2* signals by suppressing long T1 signals. This method does not require any ill-conditioned data processing and therefore provides high-quality images. In this study, the phase of the ViSTa signal was compared with the phase of myelin water simulated by the magnetic susceptibility model of hollow cylinder.
  
  
  RESULTS
  The phase evolutions of the ViSTa signal were similar to the simulated myelin water phase evolutions. When fiber orientation was perpendicular relative to the main magnetic field, both the ViSTa and the simulated myelin water phase showed large positive frequency shifts, whereas the gradient echo phase showed a slightly negative frequency shift. Additionally, the myelin water phase map generated using diffusion tensor imaging (DTI) information revealed a good match with the ViSTa phase image.
  
  
  CONCLUSIONS
  The results of this study support the origin of ViSTa signal as myelin water. ViSTa phase may potentially provide sensitivity to demyelination.
authors.affiliation: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Signal and Image Processing Institute, Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Daeun
authors.initials: D
authors.lastname: Kim
authors.affiliation: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Hyo Min
authors.initials: HM
authors.lastname: Lee
authors.affiliation: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Imaging Institute, Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Se-Hong
authors.initials: SH
authors.lastname: Oh
authors.affiliation: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Electrical and Computer Engineering, School of Engineering, Seoul National University, Seoul, Korea.
authors.forename: Jongho
authors.initials: J
authors.lastname: Lee
mesh_terms: D000465:Algorithms; D015415:Biomarkers / Q000378:metabolism; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D009186:Myelin Sheath / Q000378:metabolism*; D009413:Nerve Fibers, Myelinated / Q000378:metabolism* / Q000648:ultrastructure*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers
keywords: ViSTa phase imaging; frequency shift; hollow cylinder model; magnetic susceptibility of myelin; microstructure in white mater; myelin water imaging