title: Accelerated multi-shot diffusion imaging.
abstract: OBJECTIVE
  To reduce image distortion in MR diffusion imaging using an accelerated multi-shot method.
  
  
  METHODS
  The proposed method exploits the fact that diffusion-encoded data tend to be sparse when represented in the kb-kd space, where kb and kd are the Fourier transform duals of b and d, the b-factor and the diffusion direction, respectively. Aliasing artifacts are displaced toward under-used regions of the kb-kd plane, allowing nonaliased signals to be recovered. A main characteristic of the proposed approach is how thoroughly the navigator information gets used during reconstruction: The phase of navigator images is used for motion correction, while the magnitude of the navigator signal in kb-kd space is used for regularization purposes. As opposed to most acceleration methods based on compressed sensing, the proposed method reduces the number of ky lines needed for each diffusion-encoded image, but not the total number of images required. Consequently, it tends to be most effective at reducing image distortion rather than reducing total scan time.
  
  
  RESULTS
  Results are presented for three volunteers with acceleration factors ranging from 4 to 8, with and without the inclusion of parallel imaging.
  
  
  CONCLUSIONS
  An accelerated motion-corrected diffusion imaging method was introduced that achieves good image quality at relatively high acceleration factors.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Bruno
authors.initials: B
authors.lastname: Madore
authors.forename: Jr-yuan George
authors.initials: JY
authors.lastname: Chiou
authors.forename: Renxin
authors.initials: R
authors.lastname: Chu
authors.forename: Tzu-Cheng
authors.initials: TC
authors.lastname: Chao
authors.forename: Stephan E
authors.initials: SE
authors.lastname: Maier
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: accelerated imaging; diffusion imaging; multi-shot EPI; navigator echoes