title: Liver methylene fraction by dual- and triple-echo gradient-echo imaging at 3.0T: Correlation with proton MR spectroscopy and estimation of robustness after SPIO administration.
abstract: OBJECTIVE
  To assess the systematic errors in liver methylene fraction (LMF) resulting from fat-fat interference effects with dual- and triple-echo gradient-recalled-echo Dual/Triple GRE) sequences and to test the robustness of these sequences after iron overloading.
  
  
  METHODS
  Forty type-2 diabetic patients underwent LMF measurement by 3.0T ¹H magnetic resonance spectroscopy (corrected for T1 and T2 decays) as the reference standard and liver fat fraction (%Fat) measurement by four Dual/Triple GRE sequences with 20° and 60° flip angle (α), corrected for T1 recovery. The same four sequences were repeated in eight patients after ferumoxide injection. Corrections for systematic errors were determined from the linear regressions (spectroscopy LMF values over Dual/Triple GRE %Fat values). Robustness was tested using Wilcoxon's signed-rank test.
  
  
  RESULTS
  Fat-fat interference effects produced a ∼10% relative systematic error and T2* decay produced a 1.9%-4.2% absolute systematic error in LMF. When comparing before and after ferumoxide, dual-echo imaging with α = 20° and α = 60°, even when corrected, showed absolute differences of 7.23% [2.81%-10.25%] (P = 0.0117) and 5.65% [1.89%-8.216.8%] (P = 0.0117), respectively; compared to only 1.17% [0.08%-2.83%] (P = 0.0251) and 1.15% [0.37%-2.73%] (P = 0.2626) with triple-echo imaging and α = 20° and α = 60°, respectively.
  
  
  CONCLUSIONS
  Triple-echo imaging with α = 60° corrected for both T1 recovery and fat-fat interference effects is robust after superparamagnetic iron oxide (SPIO) administration and can reliably quantify LMF.
authors.affiliation: University of Burgundy, INSERM U866, Dijon, France. Boris.guiu@chu-dijon.fr
authors.forename: Boris
authors.initials: B
authors.lastname: Guiu
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Petit
authors.forename: Romaric
authors.initials: R
authors.lastname: Loffroy
authors.forename: Serge
authors.initials: S
authors.lastname: Aho
authors.forename: Douraied
authors.initials: D
authors.lastname: Ben Salem
authors.forename: David
authors.initials: D
authors.lastname: Masson
authors.forename: Isabelle
authors.initials: I
authors.lastname: Robin
authors.forename: Bruno
authors.initials: B
authors.lastname: Vergès
authors.forename: Patrick
authors.initials: P
authors.lastname: Hillon
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Cercueil
authors.forename: Denis
authors.initials: D
authors.lastname: Krausé
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism* / Q000473:pathology; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D017554:Carbon Compounds, Inorganic / Q000378:metabolism*; D003287:Contrast Media / Q000008:administration & dosage; D003911:Dextrans / Q000493:pharmacokinetics*; D017352:Echo-Planar Imaging / Q000379:methods; D005234:Fatty Liver / Q000150:complications / Q000175:diagnosis / Q000378:metabolism; D005260:Female; D006801:Humans; D019190:Iron Overload / Q000150:complications / Q000175:diagnosis / Q000378:metabolism*; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D014018:Tissue Distribution
chemical_list: D015415:Biomarkers; D017554:Carbon Compounds, Inorganic; D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D011522:Protons; C065507:ferumoxides