MAGNETIC RESONANCE Fat deposition decreases diffusion parameters at MRI: a study in phantoms and patients with liver steatosis Helena S. Leitão & Sabrina Doblas & Gaspard d’Assignies & Philippe Garteiser & Jean-Luc Daire & Valérie Paradis & Carlos F. G. C. Geraldes & Valérie Vilgrain & Bernard E. Van Beers Received: 25 April 2012 / Revised: 19 June 2012 / Accepted: 29 June 2012 / Published online: 1 September 2012 # European Society of Radiology 2012 Abstract Purpose Assess the effect of fat deposition on the MRI diffusion coefficients in lipid emulsion-based phantoms and patients with proven isolated liver steatosis. Materials and 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 0 14) or isolated liver steatosis (n 0 5) proven by histopathology. The ap- parent, 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 phan- toms. 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 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 0.298). Conclusions Fat deposition decreases the apparent and pure diffusion coefficients in lipid emulsion-based phan- toms and patients with isolated liver steatosis proven by histopathology. Key Points • Magnetic resonance imaging is increasingly used to quantify hepatic fibrosis. • Lipid phantoms show inverse correlations between diffusion coefficients and fat fractions. • The pure diffusion coefficient decreases in patients with isolated liver steatosis. • Steatosis may be a confounding factor when measuring the liver diffusion parameters. Keywords Liver . Steatosis . Magnetic resonance imaging . Diffusion-weighted MRI . Phantom imaging Chronic liver diseases are frequent causes of morbidity and mortality in the Western countries. In a recent screening H. S. Leitão Center for Neuroscience and Cell Biology, PhD Program in Experimental Biology and Biomedicine, University of Coimbra, Coimbra, Portugal H. S. Leitão : S. Doblas : G. d’Assignies : P. Garteiser : J.-L. Daire : V. Vilgrain : B. E. Van Beers Laboratory of Physiological and Molecular Imaging of the Abdomen (IPMA) and Department of Radiology, University Paris Diderot, Sorbonne Paris Cité, INSERM UMR 773, University Hospitals Paris Nord Val de Seine, Beaujon, Clichy, France V. Paradis Department of Pathology, University Paris Diderot, Sorbonne Paris Cité, INSERM UMR 773, University Hospitals Paris Nord Val de Seine, Beaujon, Clichy, France C. F. G. C. Geraldes Department of Life Sciences, Faculty of Science and Technology, Center for Neuroscience and Cell Biology and Coimbra Chemistry Center, University of Coimbra, Coimbra, Portugal H. S. Leitão (*) Department of Radiology and IPMA, INSERM UMR 773, University Hospitals Paris Nord Val de Seine, Beaujon, 100 boulevard du Général Leclerc, 92110 Clichy, France e-mail: helenasleitao@netcabo.pt Eur Radiol (2013) 23:461–467 DOI 10.1007/s00330-012-2626-8