title: Quantification of early fatty infiltration of the rotator cuff muscles: comparison of multi-echo Dixon with single-voxel MR spectroscopy.
abstract: OBJECTIVE
  To evaluate quantification of early fatty infiltration in supraspinatus muscles with magnetic resonance (MR) imaging using a T2*-corrected multi-echo 3D-gradient-echo Dixon-based sequence (multi-echo Dixon) and compare it to proton-MR-spectroscopy.
  
  
  METHODS
  Sixty subjects (mean age 46 years, 41 men) with good supraspinatus muscle quality on 1.5 T MR imaging were included. Fat percentage (FP) in the supraspinatus muscle was quantified using a multi-echo Dixon compared to single-voxel MR spectroscopy as reference standard. In 18 subjects the multi-echo Dixon was repeated to assess test-retest reliability. Measurements based on multi-echo Dixon were performed by two independent readers by placing regions-of-interest (ROIs) in the supraspinatus muscle corresponding to the MR-spectroscopy voxel. Intraclass and concordance correlation coefficients (ICC/CCC) were used for statistical analysis.
  
  
  RESULTS
  Test-retest reliability was substantial for reader 1 (ICC = 0.757) and almost perfect for reader 2 (ICC = 0.873). Inter-reader reliability for multi-echo Dixon was almost perfect (ICC = 0.893, P < .0005). Mean FP in all 60 subjects with multi-echo Dixon was 3.5 ± 1.6 for reader 1, 3.7 ± 1.8 for reader 2, and 2.8 ± 1.4 with MR spectroscopy. Correlation between multi-echo Dixon and MR spectroscopy was moderate (CCC = 0.641).
  
  
  CONCLUSIONS
  The multi-echo Dixon sequence is a reliable method and comparable to MR-spectroscopy for quantification of low levels of fatty infiltration in the supraspinatus muscle.
  
  
  CONCLUSIONS
  • Multi-echo Dixon for low fat quantification in muscles is reliable. • Multi-echo Dixon low fat quantification is comparable to single-voxel MR spectroscopy • Multi-echo Dixon detects substantial differences in fatty infiltration within Goutallier 0-1.
authors.affiliation: Radiology, Balgrist University Hospital, Forchstrasse 340, CH-8008, Zurich, Switzerland. christoph.agten@balgrist.ch.|Faculty of Medicine, University of Zurich, Zurich, Switzerland. christoph.agten@balgrist.ch.
authors.forename: Christoph A
authors.identifier: http://orcid.org/0000-0003-1861-541X
authors.initials: CA
authors.lastname: Agten
authors.affiliation: Radiology, Balgrist University Hospital, Forchstrasse 340, CH-8008, Zurich, Switzerland.|Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Rosskopf
authors.affiliation: Orthopaedic Surgery, Balgrist University Hospital, Forchstrasse 340, CH-8008, Zurich, Switzerland.|Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Gerber
authors.affiliation: Radiology, Balgrist University Hospital, Forchstrasse 340, CH-8008, Zurich, Switzerland.|Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D017006:Rotator Cuff / Q000000981:diagnostic imaging* / Q000473:pathology; D055815:Young Adult
keywords: Magnetic resonance imaging; Multi-echo Dixon; Muscle fat quantification; Rotator cuff; Spectroscopy