title: Intravoxel incoherent motion diffusion-weighted imaging in the liver: comparison of mono-, bi- and tri-exponential modelling at 3.0-T.
abstract: OBJECTIVE
  To determine whether a mono-, bi- or tri-exponential model best fits the intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) signal of normal livers.
  
  
  METHODS
  The pilot and validation studies were conducted in 38 and 36 patients with normal livers, respectively. The DWI sequence was performed using single-shot echoplanar imaging with 11 (pilot study) and 16 (validation study) b values. In each study, data from all patients were used to model the IVIM signal of normal liver. Diffusion coefficients (Di ± standard deviations) and their fractions (fi ± standard deviations) were determined from each model. The models were compared using the extra sum-of-squares test and information criteria.
  
  
  RESULTS
  The tri-exponential model provided a better fit than both the bi- and mono-exponential models. The tri-exponential IVIM model determined three diffusion compartments: a slow (D1 = 1.35 ± 0.03 × 10(-3) mm(2)/s; f1 = 72.7 ± 0.9 %), a fast (D2 = 26.50 ± 2.49 × 10(-3) mm(2)/s; f2 = 13.7 ± 0.6 %) and a very fast (D3 = 404.00 ± 43.7 × 10(-3) mm(2)/s; f3 = 13.5 ± 0.8 %) diffusion compartment [results from the validation study]. The very fast compartment contributed to the IVIM signal only for b values ≤15 s/mm(2) CONCLUSION: The tri-exponential model provided the best fit for IVIM signal decay in the liver over the 0-800 s/mm(2) range. In IVIM analysis of normal liver, a third very fast (pseudo)diffusion component might be relevant.
  
  
  CONCLUSIONS
  • For normal liver, tri-exponential IVIM model might be superior to bi-exponential • A very fast compartment (D = 404.00 ± 43.7 × 10 (-3) mm (2) /s; f = 13.5 ± 0.8 %) is determined from the tri-exponential model • The compartment contributes to the IVIM signal only for b ≤ 15 s/mm(2).
authors.affiliation: University of Burgundy, INSERM U866, BP 87900, 21079, Dijon, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Cercueil
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Petit
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Nougaret
authors.forename: Philippe
authors.initials: P
authors.lastname: Soyer
authors.forename: Audrey
authors.initials: A
authors.lastname: Fohlen
authors.forename: Marie-Ange
authors.initials: MA
authors.lastname: Pierredon-Foulongne
authors.forename: Valentina
authors.initials: V
authors.lastname: Schembri
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Delhom
authors.forename: Sabine
authors.initials: S
authors.lastname: Schmidt
authors.forename: Alban
authors.initials: A
authors.lastname: Denys
authors.forename: Serge
authors.initials: S
authors.lastname: Aho
authors.forename: Boris
authors.initials: B
authors.lastname: Guiu
mesh_terms: D000328:Adult; D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008099:Liver / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009038:Motion; D010865:Pilot Projects; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D055815:Young Adult