title: Short- and midterm reproducibility of marrow fat measurements using mDixon imaging in healthy postmenopausal women.
abstract: OBJECTIVE
  We tested the short- and midterm reproducibility of vertebral marrow fat fraction (FF) measurements using mDixon imaging.
  
  
  METHODS
  Thirty postmenopausal women underwent mDixon scans to obtain L1-4 FF from three slices per vertebra by two independent observers (session 1). Measurements were repeated after 6 weeks (session 2) and 6 months (session 3). The mean FF for three regions of interest per vertebra was calculated. The coefficients of variation (CVs) were calculated for each participant and imaging session, and the intraclass correlation coefficients (ICCs) were calculated to assess interobserver and intersession agreements.
  
  
  RESULTS
  There were no significant differences in FF measurements among the three slices, imaging sessions or observers. The mean intrasubject CV for FF measurement reproducibility was 1.94 %. The interobserver agreement for the average FF value was excellent (ICC ≥0.945 for each session). The ICC for intersession agreement was excellent (ICC ≥0.955 between sessions). The mean intersession CV was lower within a short-term interval (2.97 %) than within sessions 1 and 3 (4.80 %) or sessions 3 and 2 (4.44 %). The overall mean CV for the reproducibility of FF measured with mDixon imaging over the short- and midterm was 4.09 % (95 % CI, 3.79-4.40 %).
  
  
  CONCLUSIONS
  mDixon is a reproducible method for FF quantification over short- and midterm intervals up to 6 months in healthy postmenopausal women. Our results also provide data by which a power analysis can be optimized when designing studies involving the use of FF derived from similar mDixon sequences.
authors: Department of Radiology, Yueyang Hospital, Shanghai University of Traditional Chinese Medicine, 110 Ganhe Rd, Hongkou District, Shanghai, 200437, China. purenyi@163.com.
authors: Guanwu
authors: G
authors: Li
authors: Xinzhuang Community Health Center, Shanghai, 201199, China.
authors: Zheng
authors: Z
authors: Xu
authors: Department of Spinal Disease Unit, Yueyang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200437, China.
authors: Wei
authors: W
authors: Yuan
authors: Department of Radiology, Yueyang Hospital, Shanghai University of Traditional Chinese Medicine, 110 Ganhe Rd, Hongkou District, Shanghai, 200437, China.
authors: Shixin
authors: S
authors: Chang
authors: Department of Radiology, Wayne State University, Detroit, 48202, MI, USA.
authors: Yongsheng
authors: Y
authors: Chen
authors: Department of Radiology, Wayne State University, Detroit, 48202, MI, USA.
authors: Horea
authors: H
authors: Calimente
authors: Department of Radiology, Wayne State University, Detroit, 48202, MI, USA.
authors: Jiani
authors: J
authors: Hu
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000886:Anthropometry / Q000379:methods*; D001853:Bone Marrow / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D017698:Postmenopause; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013131:Spine / Q000000981:diagnostic imaging*
keywords: Fat fraction; Reproducibility; Spine; Water-fat separation