title: Fat deposition decreases diffusion parameters at MRI: a study in phantoms and patients with liver steatosis.
abstract: OBJECTIVE
  Assess the effect of fat deposition on the MRI diffusion coefficients in lipid emulsion-based phantoms and patients with proven isolated liver steatosis.
  
  
  METHODS
  Diffusion-weighted MRI with 11 b values from 0-500 s/mm(2) was performed in phantoms (fat fractions 0-18 %) with and without fat suppression and in 19 patients with normal liver (n = 14) or isolated liver steatosis (n = 5) proven by histopathology. The apparent, pure and perfusion-related diffusion coefficients and the perfusion fraction were measured. Spearman correlation coefficient and Mann-Whitney U test were used for comparisons.
  
  
  RESULTS
  A strong correlation between the apparent and pure diffusion coefficients and fat fractions was seen in phantoms. The pure diffusion coefficient decreased significantly in patients with liver steatosis (0.96 ± 0.16 × 10(-3) mm(2)/s versus 1.18 ± 0.09 × 10(-3) mm(2)/s in normal liver, P = 0.005), whereas the decrease in apparent diffusion coefficient did not reach statistical significance (1.26 ± 0.25 × 10(-3) mm(2)/s versus 1.41 ± 0.14 × 10(-3) mm(2)/s in normal liver, P = 0.298).
  
  
  CONCLUSIONS
  Fat deposition decreases the apparent and pure diffusion coefficients in lipid emulsion-based phantoms and patients with isolated liver steatosis proven by histopathology.
authors.affiliation: Center for Neuroscience and Cell Biology, PhD Program in Experimental Biology and Biomedicine, University of Coimbra, Coimbra, Portugal. helenasleitao@netcabo.pt
authors.forename: Helena S
authors.initials: HS
authors.lastname: Leitão
authors.forename: Sabrina
authors.initials: S
authors.lastname: Doblas
authors.forename: Gaspard
authors.initials: G
authors.lastname: d'Assignies
authors.forename: Philippe
authors.initials: P
authors.lastname: Garteiser
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Daire
authors.forename: Valérie
authors.initials: V
authors.lastname: Paradis
authors.forename: Carlos F G C
authors.initials: CF
authors.lastname: Geraldes
authors.forename: Valérie
authors.initials: V
authors.lastname: Vilgrain
authors.forename: Bernard E
authors.initials: BE
authors.lastname: Van Beers
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism / Q000473:pathology*; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005234:Fatty Liver / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D012016:Reference Values; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D055815:Young Adult