title: Diffusion-weighted imaging of the liver with multiple b values: effect of diffusion gradient polarity and breathing acquisition on image quality and intravoxel incoherent motion parameters--a pilot study.
abstract: OBJECTIVE
  To optimize intravoxel incoherent motion (IVIM) diffusion-weighted (DW) imaging by estimating the effects of diffusion gradient polarity and breathing acquisition scheme on image quality, signal-to-noise ratio (SNR), IVIM parameters, and parameter reproducibility, as well as to investigate the potential of IVIM in the detection of hepatic fibrosis.
  
  
  METHODS
  In this institutional review board-approved prospective study, 20 subjects (seven healthy volunteers, 13 patients with hepatitis C virus infection; 14 men, six women; mean age, 46 years) underwent IVIM DW imaging with four sequences: (a) respiratory-triggered (RT) bipolar (BP) sequence, (b) RT monopolar (MP) sequence, (c) free-breathing (FB) BP sequence, and (d) FB MP sequence. Image quality scores were assessed for all sequences. A biexponential analysis with the Bayesian method yielded true diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (PF) in liver parenchyma. Mixed-model analysis of variance was used to compare image quality, SNR, IVIM parameters, and interexamination variability between the four sequences, as well as the ability to differentiate areas of liver fibrosis from normal liver tissue.
  
  
  RESULTS
  Image quality with RT sequences was superior to that with FB acquisitions (P = .02) and was not affected by gradient polarity. SNR did not vary significantly between sequences. IVIM parameter reproducibility was moderate to excellent for PF and D, while it was less reproducible for D*. PF and D were both significantly lower in patients with hepatitis C virus than in healthy volunteers with the RT BP sequence (PF = 13.5% ± 5.3 [standard deviation] vs 9.2% ± 2.5, P = .038; D = [1.16 ± 0.07] × 10(-3) mm(2)/sec vs [1.03 ± 0.1] × 10(-3) mm(2)/sec, P = .006).
  
  
  CONCLUSIONS
  The RT BP DW imaging sequence had the best results in terms of image quality, reproducibility, and ability to discriminate between healthy and fibrotic liver with biexponential fitting.
authors.affiliation: Department of Radiology, Body MRI and Translational and Molecular Imaging Institute, Division of Liver Diseases, Mount Sinai School of Medicine, One Gustave Levy Place, Box 1234, New York, NY 10029, USA.
authors.forename: Hadrien A
authors.initials: HA
authors.lastname: Dyvorne
authors.forename: Nicola
authors.initials: N
authors.lastname: Galea
authors.forename: Thomas
authors.initials: T
authors.lastname: Nevers
authors.forename: M Isabel
authors.initials: MI
authors.lastname: Fiel
authors.forename: David
authors.initials: D
authors.lastname: Carpenter
authors.forename: Edmund
authors.initials: E
authors.lastname: Wong
authors.forename: Matthew
authors.initials: M
authors.lastname: Orton
authors.forename: Andre
authors.initials: A
authors.lastname: de Oliveira
authors.forename: Thorsten
authors.initials: T
authors.lastname: Feiweier
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Vachon
authors.forename: James S
authors.initials: JS
authors.lastname: Babb
authors.forename: Bachir
authors.initials: B
authors.lastname: Taouli
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D016477:Artifacts; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008103:Liver Cirrhosis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009038:Motion; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity; D055815:Young Adult