title: DWI using navigated interleaved multishot EPI with realigned GRAPPA reconstruction.
abstract: OBJECTIVE
  A novel k-space reconstruction method is proposed for generating diffusion-weighted imaging (DWI) using navigated interleaved multishot EPI (msEPI).
  
  
  METHODS
  In interleaved msEPI, each shot of data acquired from one coil channel is a subset of the full k-space of that channel. All the k-space subsets of one channel can be treated as an undersampled dataset of a virtual multichannel data, which can be reconstructed by the GRAPPA algorithm after k-space realignment. The intershot phase variations are directly compensated using navigator echoes as the auto-calibrating data in GRAPPA reconstruction. In cases of multichannel msEPI data, all the virtual channels and actual channels can be integrated into a single GRAPPA reconstruction step. The proposed method is tested using both simulation and in-vivo data. The simulation results produced by the proposed method and a SENSE-based method are compared.
  
  
  RESULTS
  The simulated images generated by the proposed method exhibit less relative error compared with those generated by the SENSE method. Inconsistent shot-to-shot phase variation is naturally resolved by GRAPPA calibration without additional phase map processing. High-quality brain DWI with submillimeter resolution is obtained using our proposed reconstruction method.
  
  
  CONCLUSIONS
  A novel k-space msEPI reconstruction method has been developed for generating high-quality diffusion imaging.
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.|Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
authors.forename: Wentao
authors.initials: W
authors.lastname: Liu
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.|Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
authors.forename: Xuna
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.|Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.|Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Tang
authors.affiliation: Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.|Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.|McGovern Institute for Brain Research, Peking University, Beijing, China.
authors.forename: Jia-Hong
authors.initials: JH
authors.lastname: Gao
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D064847:Multimodal Imaging / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013382:Subtraction Technique
keywords: diffusion imaging; multishot EPI; navigator; realigned GRAPPA