title: Motion artifact reduction of diffusion-weighted MRI of the liver: use of velocity-compensated diffusion gradients combined with tetrahedral gradients.
abstract: OBJECTIVE
  To assess the effect of motion artifact reduction on the diffusion-weighted magnetic resonance imaging (DWI-MRI) of the liver, we compared velocity-compensated DWI (VC-DWI) and VC-DWI combined with tetrahedral gradients (t-VC-DWI) to conventional DWI (c-DWI) in the assessment of apparent diffusion coefficients (ADCs) of the liver.
  
  
  METHODS
  In 12 healthy volunteers, the liver was scanned with c-DWI, VC-DWI, and t-VC-DWI sequences. The signal-to-noise ratio (SNR) and ADC of the liver parenchyma were measured and compared among sequences.
  
  
  RESULTS
  The image quality was visually better for t-VC-DWI than for the others. The SNR for t-VC-DWI was significantly higher than that for VC-DWI (P < 0.05) and comparable to that for c-DWI. ADCs in both hepatic lobes were significantly lower for t-VC-DWI than for c-DWI (P < 0.01). ADC in the left lobe was significantly lower for VC-DWI than for c-DWI (P < 0.01). Although ADC in the left lobe was significantly higher for c-DWI (P < 0.01), no significant differences in ADCs were found between the right and left lobes for VC-DWI and t-VC-DWI.
  
  
  CONCLUSIONS
  The use of a t-VC-DWI sequence enables us to correct ADCs of the liver for artificial elevation due to cardiac motion, with preserved SNR.
authors.affiliation: School of Allied Health Sciences, Kitasato University, Kanagawa, Japan. m.ozaki@kitasato-u.ac.jp
authors.forename: Masanori
authors.initials: M
authors.lastname: Ozaki
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Inoue
authors.forename: Tosiaki
authors.initials: T
authors.lastname: Miyati
authors.forename: Hirohumi
authors.initials: H
authors.lastname: Hata
authors.forename: Sinya
authors.initials: S
authors.lastname: Mizukami
authors.forename: Shotaro
authors.initials: S
authors.lastname: Komi
authors.forename: Keiji
authors.initials: K
authors.lastname: Matsunaga
authors.forename: Reiko
authors.initials: R
authors.lastname: Woodhams
mesh_terms: D000328:Adult; D016477:Artifacts; D003952:Diagnostic Imaging / Q000379:methods; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008099:Liver / Q000473:pathology*; D008297:Male; D015233:Models, Statistical; D009038:Motion; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio