title: Fat quantification using an interleaved bipolar acquisition.
abstract: OBJECTIVE
  To demonstrate a new multigradient echo bipolar acquisition sequence for fat quantification.
  
  
  METHODS
  A multiecho bipolar acquisition is used such that the even echoes have opposite polarity to the odd echoes. In addition, the readout gradients alternate their polarities every other phase-encode line. Each echo, therefore, consists of phase-encode lines with both positive and negative polarities. Phase-encodes acquired with the same polarity are grouped together, and parallel imaging reconstruction is used to obtain two full k-space maps with opposite readout polarities at all the echoes. By complex averaging, the inconsistent phase errors between odd and even echoes are removed and water/fat separation techniques used with conventional unipolar sequences can be performed.
  
  
  RESULTS
  Phantoms and in vivo experiments demonstrated accurate fat fraction and increased signal to noise ratio efficiency compared with the established unipolar acquisition. Artefacts due to phase and magnitude errors of bipolar acquisition were eliminated in all experiments.
  
  
  CONCLUSIONS
  The interleaved bipolar sequence is an efficient technique for fat quantification. It demonstrated accurate fat measurements in a shorter scan time compared with the standard unipolar sequence.
authors.affiliation: Biomedical Engineering, Western University, London, Canada.|Robarts Research Institute, Western University, London, Canada.
authors.forename: Abraam S
authors.initials: AS
authors.lastname: Soliman
authors.affiliation: Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Curtis N
authors.initials: CN
authors.lastname: Wiens
authors.affiliation: Robarts Research Institute, Western University, London, Canada.|Department of Medical Biophysics, Western University, London, Canada.
authors.forename: Trevor P
authors.initials: TP
authors.lastname: Wade
authors.affiliation: Biomedical Engineering, Western University, London, Canada.|Robarts Research Institute, Western University, London, Canada.|Department of Medical Biophysics, Western University, London, Canada.
authors.forename: Charles A
authors.initials: CA
authors.lastname: McKenzie
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000465:Algorithms; D016477:Artifacts; D002138:Calibration; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007717:Knee / Q000000981:diagnostic imaging; D008099:Liver / Q000000981:diagnostic imaging; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging; D015233:Models, Statistical; D019047:Phantoms, Imaging; D059629:Signal-To-Noise Ratio
keywords: IDEAL imaging; bipolar acquisition; chemical-shift imaging; fat quantification