title: Hepatic fat quantification using the two-point Dixon method and fat color maps based on non-alcoholic fatty liver disease activity score.
abstract: OBJECTIVE
  The two-point Dixon method for magnetic resonance imaging (MRI) is commonly used to non-invasively measure fat deposition in the liver. The aim of the present study was to assess the usefulness of MRI-fat fraction (MRI-FF) using the two-point Dixon method based on the non-alcoholic fatty liver disease activity score.
  
  
  METHODS
  This retrospective study included 106 patients who underwent liver MRI and MR spectroscopy, and 201 patients who underwent liver MRI and histological assessment. The relationship between MRI-FF and MR spectroscopy-fat fraction was used to estimate the corrected MRI-FF for hepatic multi-peaks of fat. Then, a color FF map was generated with the corrected MRI-FF based on the non-alcoholic fatty liver disease activity score. We defined FF variability as the standard deviation of FF in regions of interest. Uniformity of hepatic fat was visually graded on a three-point scale using both gray-scale and color FF maps. Confounding effects of histology (iron, inflammation and fibrosis) on corrected MRI-FF were assessed by multiple linear regression.
  
  
  RESULTS
  The linear correlations between MRI-FF and MR spectroscopy-fat fraction, and between corrected MRI-FF and histological steatosis were strong (R2= 0.90 and R2= 0.88, respectively). Liver fat variability significantly increased with visual fat uniformity grade using both of the maps (ρ = 0.67-0.69, both P < 0.001). Hepatic iron, inflammation and fibrosis had no significant confounding effects on the corrected MRI-FF (all P > 0.05).
  
  
  CONCLUSIONS
  The two-point Dixon method and the gray-scale or color FF maps based on the non-alcoholic fatty liver disease activity score were useful for fat quantification in the liver of patients without severe iron deposition.
authors.affiliation: Department of Radiological Technology, Toranomon Hospital, Tokyo, Japan.|Okinaka Memorial Institute for Medical Research, Tokyo, Japan.|Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan.|Department of Medical Radiology, Faculty of Medical Technology, Teikyo University, Tokyo, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: Okinaka Memorial Institute for Medical Research, Tokyo, Japan.|Department of Hepatology, Toranomon Hospital, Tokyo, Japan.|Department of Radiology, Toranomon Hospital, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Saitoh
authors.affiliation: Department of Radiological Technology, Toranomon Hospital, Tokyo, Japan.|Okinaka Memorial Institute for Medical Research, Tokyo, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Takahashi
authors.affiliation: Department of Radiological Technology, Toranomon Hospital, Tokyo, Japan.|Okinaka Memorial Institute for Medical Research, Tokyo, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Tsuji
authors.affiliation: Okinaka Memorial Institute for Medical Research, Tokyo, Japan.|Department of Hepatology, Toranomon Hospital, Tokyo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: Okinaka Memorial Institute for Medical Research, Tokyo, Japan.|Department of Hepatology, Toranomon Hospital, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Okinaka Memorial Institute for Medical Research, Tokyo, Japan.|Department of Hepatology, Toranomon Hospital, Tokyo, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kawamura
authors.affiliation: Okinaka Memorial Institute for Medical Research, Tokyo, Japan.|Department of Pathology, Toranomon Hospital, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fujii
authors.affiliation: Department of Ophthalmology, Japan Community Health Care Organization Tokyo Shinjuku Medical Center, Tokyo, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan.
authors.forename: Tosiaki
authors.initials: T
authors.lastname: Miyati
authors.affiliation: Okinaka Memorial Institute for Medical Research, Tokyo, Japan.|Department of Hepatology, Toranomon Hospital, Tokyo, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Kumada
keywords: fatty liver; magnetic resonance imaging; non-alcoholic fatty liver disease; non-alcoholic steatohepatitis