title: Quantitative evaluation of fatty degeneration of the supraspinatus and infraspinatus muscles using T2 mapping.
abstract: BACKGROUND
  Although fatty degeneration of the rotator cuff muscles has been reported to affect the outcomes of rotator cuff repairs, only a few studies have attempted to quantitatively evaluate this degeneration. T2 mapping is a quantitative magnetic resonance imaging technique that potentially evaluates the concentration of fat in muscles. The purpose of this study was to investigate fatty degeneration of the rotator cuff muscles by using T2 mapping, as well as to evaluate the reliability of T2 measurement.
  
  
  METHODS
  We obtained magnetic resonance images including T2 mapping from 184 shoulders (180 patients; 110 male patients [112 shoulders] and 70 female patients [72 shoulders]; mean age, 62 years [range, 16-84 years]). Eighty-three shoulders had no rotator cuff tear (group A), whereas 101 shoulders had tears, of which 62 were incomplete to medium (group B) and 39 were large to massive (group C). T2 values of the supraspinatus and infraspinatus muscles were measured and compared among groups. Intraobserver and interobserver variabilities also were examined.
  
  
  RESULTS
  The mean T2 values of the supraspinatus in groups A, B, and C were 36.3 ± 4.7 milliseconds, 44.2 ± 11.3 milliseconds, and 57.0 ± 18.8 milliseconds, respectively. The mean T2 values of the infraspinatus in groups A, B, and C were 36.1 ± 5.1 milliseconds, 40.0 ± 11.1 milliseconds, and 51.9 ± 18.2 milliseconds, respectively. The T2 value significantly increased with the extent of the tear in both muscles. Both intraobserver and interobserver variabilities were more than 0.99.
  
  
  CONCLUSIONS
  T2 mapping can be a reliable tool to quantify fatty degeneration of the rotator cuff muscles.
authors.affiliation: Department of Orthopaedic Surgery, Teikyo University Chiba Medical Center, Ichihara, Japan. Electronic address: keisk-m@bf6.so-net.ne.jp.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Matsuki
authors.affiliation: Department of Orthopaedic Surgery, Teikyo University Chiba Medical Center, Ichihara, Japan.
authors.forename: Atsuya
authors.initials: A
authors.lastname: Watanabe
authors.affiliation: Department of Orthopaedic Surgery, Teikyo University Chiba Medical Center, Ichihara, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Ochiai
authors.affiliation: Department of Orthopaedic Surgery, Kitazato University East Hospital, Sagamihara, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kenmoku
authors.affiliation: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Nobuyasu
authors.initials: N
authors.lastname: Ochiai
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Obata
authors.affiliation: Department of Orthopaedic Surgery, Teikyo University Chiba Medical Center, Ichihara, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Toyone
authors.affiliation: Department of Orthopaedic Surgery, Teikyo University Chiba Medical Center, Ichihara, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Wada
authors.affiliation: Department of Radiology, Teikyo University Chiba Medical Center, Ichihara, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Okubo
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; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000473:pathology*; D000070636:Rotator Cuff Injuries; D013708:Tendon Injuries / Q000175:diagnosis* / Q000473:pathology; D055815:Young Adult
keywords: Shoulder; T2 mapping; fatty degeneration; infraspinatus; magnetic resonance imaging; rotator cuff tear; supraspinatus