title: Diffusion-weighted magnetic resonance imaging for staging liver fibrosis is less reliable in the presence of fat and iron.
abstract: OBJECTIVE
  To investigate the reliability of diffusion-weighted magnetic resonance imaging (DW-MRI) for staging liver fibrosis in the presence of fat and iron.
  
  
  METHODS
  Ninety-five patients, including 48 men and 47 women, aged 57.0 ± 14.2 years, underwent liver biopsy. Ninety-six samples were histologically staged for liver fibrosis (0-Ishak score 0; 1-Ishak score 1-4; 2-Ishak score 5-6) and semiquantitatively graded for hepatic iron (0, no; 1, low; 2, moderate; 3, high iron) and for hepatic steatosis. Within 72 h after biopsy, navigator-triggered DW-MRI using b-values of 50/400/800 s/mm(2) was performed in a 1.5-T system, and apparent diffusion coefficients (ADC) were analysed. ADCs were correlated with fibrosis stage, steatosis grade, and iron grade using linear regression.
  
  
  RESULTS
  ADC did not correlate with fibrosis stages in either the overall group (n = 96; R (2) = 0.38; P = 0.17) or in the subgroup without liver iron and steatosis (n = 40; R (2) = 0.01; P = 0.75). ADC decreased significantly with steatosis grade in cases without iron and fibrosis (n = 42; R (2) = 0.28; ß = -5.3; P < 0.001). Liver iron was modestly correlated with ADC in patients without fibrosis and steatosis (n = 33; R (2) = 0.29; P = 0.04), whereas high iron concentrations were associated with low ADC values (group 3: β = -489; P = 0.005; reference:group 0) but intermediate levels were not (group 1/group 2: P = 0.93/P = 0.54; reference group: 0).
  
  
  CONCLUSIONS
  ADC values are confounded by fat and iron. However, even in patients without fat or iron, DW-MRI does not adequately discriminate the stage of fibrosis.
  
  
  CONCLUSIONS
  • Diffusion-weighted magnetic resonance imaging (DW-MRI) is increasingly used to evaluate liver disease. • DWI using b-values of 50/400/800 s/mm (2) does not adequately quantify fibrosis. • Assessment of the apparent diffusion coefficient (ADC) is confounded by fat and iron. • Fat may influence ADCs by altering water diffusion. • Iron may influence ADCs by signal decay and noise floor effects.
authors.affiliation: Department of Radiology and Neuroradiology, Ernst Moritz Arndt University of Greifswald, Ferdinand-Sauerbruch-Straße NK, Greifswald 17475, Germany. buelowr@uni-greifswald.de
authors.forename: Robin
authors.initials: R
authors.lastname: Bülow
authors.forename: Birger
authors.initials: B
authors.lastname: Mensel
authors.forename: Peter
authors.initials: P
authors.lastname: Meffert
authors.forename: Diego
authors.initials: D
authors.lastname: Hernando
authors.forename: Matthias
authors.initials: M
authors.lastname: Evert
authors.forename: Jens-Peter
authors.initials: JP
authors.lastname: Kühn
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005234:Fatty Liver / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D006801:Humans; D007501:Iron / Q000032:analysis*; D008103:Liver Cirrhosis / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007501:Iron