title: Quantification of bone marrow fat content using iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL): reproducibility, site variation and correlation with age and menopause.
abstract: OBJECTIVE
  To determine the reproducibility of the quantitative chemical shift-based water-fat separation method with a multiecho gradient echo sequence [iteraterative decomposition of water and fat with echo asymmetry and least-squares estimation quantitation sequence (IDEAL-IQ)] for assessing bone marrow fat fraction (FF); to evaluate variation of FF at different bone sites; and to investigate its association with age and menopause.
  
  
  METHODS
  31 consecutive females who underwent pelvic iterative decomposition of water and fat with echo asymmetry and least-squares estimation at 3-T MRI were included in this study. Quantitative FF using IDEAL-IQ of four bone sites were analyzed. The coefficients of variance (CV) on each site were evaluated repeatedly 10 times to assess the reproducibility. Correlations between FF and age were evaluated on each site, and the FFs between pre- and post-menopausal groups were compared.
  
  
  RESULTS
  The CV in the quantification of marrow FF ranged from 0.69% to 1.70%. A statistically significant correlation was established between the FF and the age in lumbar vertebral body, ilium and intertrochanteric region of the femur (p < 0.001). The average FF of post-menopausal females was significantly higher than that of pre-menopausal females in these sites (p < 0.05). In the greater trochanter of the femur, there was no significant correlation between FF and age.
  
  
  CONCLUSIONS
  In vivo IDEAL-IQ would provide reliable quantification of bone marrow fat.
  
  
  CONCLUSIONS
  IDEAL-IQ is simple to perform in a short time and may be practical for providing information on bone quality in clinical settings.
authors.affiliation: Department of Radiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Aoki
authors.affiliation: Department of Radiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: Shinpei
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Department of Radiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kinoshita
authors.affiliation: Department of Radiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Hayashida
authors.affiliation: Department of Radiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: Yukunori
authors.initials: Y
authors.lastname: Korogi
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000328:Adult; D000367:Age Factors; D000368:Aged; D001834:Body Water / Q000378:metabolism*; D001853:Bone Marrow / Q000033:anatomy & histology*; D005260:Female; D005269:Femur / Q000033:anatomy & histology; D006801:Humans; D016018:Least-Squares Analysis; D008159:Lumbar Vertebrae / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging; D008593:Menopause / Q000378:metabolism*; D008875:Middle Aged; D015203:Reproducibility of Results; D055815:Young Adult