title: Quantification of Fatty Degeneration Within the Supraspinatus Muscle by Using a 2-Point Dixon Method on 3-T MRI.
abstract: OBJECTIVE
  The objective of this study was to quantify fatty degeneration of the supraspinatus muscle by using a 2-point Dixon technique on 3-T MRI and to evaluate the correlation of muscular atrophy and fat fraction values among different severities of rotator cuff tears across differing ages and sexes.
  
  
  METHODS
  Patients with shoulder pain (n = 359) were evaluated by shoulder MRI on a 3-T unit, including a 2-point Dixon sequence for quantification of muscle atrophy and fatty degeneration within the supraspinatus muscle. Two board-certified musculoskeletal radiologists evaluated the degree of rotator cuff tears in three groups: full-thickness tear (n = 63), partial tear (n = 54), and no tear (n = 242). In quantitative analysis, we measured signal intensity values of in-phase images (SIn) and fat images (SFat) within the supraspinatus muscle, and the fat fraction was calculated as SFat/SIn. The Thomazeau occupation ratio was used as a quantitative index of muscular atrophy. Fat fraction and muscle atrophy were evaluated among these groups.
  
  
  RESULTS
  Fat fraction values were changed with the degree of rotator cuff tears and were (mean ± SD) 0.258 ± 0.123 among patients with full-thickness tears, 0.166 ± 0.067 among patients with partial tears, and 0.128 ± 0.061 among patients with no tears, with statistically significant differences (p < 0.001). The values were higher in female than in male patients in all groups. The Pearson correlation coefficient was 0.348 between age and fat fraction value, and 0.664 between muscular atrophy rate and fat fraction value.
  
  
  CONCLUSIONS
  An increase in supraspinatus fatty degeneration was statistically significantly correlated with severity of supraspinatus tears and moderately correlated with muscular atrophy. Fatty degeneration tends to progress more rapidly than muscular atrophy in female patients, with statistically significant sex differences.
authors.affiliation: 1 Department of Radiology, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan.|2 Department of Radiological Sciences, University of California Irvine, Irvine, CA.
authors.forename: Taiki
authors.initials: T
authors.lastname: Nozaki
authors.affiliation: 3 Department of Orthopaedic Surgery, St. Luke's International Hospital, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tasaki
authors.affiliation: 1 Department of Radiology, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan.
authors.forename: Saya
authors.initials: S
authors.lastname: Horiuchi
authors.affiliation: 1 Department of Radiology, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan.
authors.forename: Chiharu
authors.initials: C
authors.lastname: Osakabe
authors.affiliation: 4 Center for Clinical Epidemiology, St. Luke's Life Science Institute, Tokyo, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Ohde
authors.affiliation: 1 Department of Radiology, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan.
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Saida
authors.affiliation: 2 Department of Radiological Sciences, University of California Irvine, Irvine, CA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoshioka
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D009133:Muscular Atrophy / Q000473:pathology*; D017006:Rotator Cuff / Q000473:pathology*; D020069:Shoulder Pain / Q000473:pathology*
keywords: MRI; fatty degeneration; muscular atrophy; quantification; rotator cuff tear