title: Improved anatomical reproducibility in quantitative lower-limb muscle MRI.
abstract: OBJECTIVE
  To compare the influence of two limb positions and slice prescription using scout-image-based and surface-anatomy-based methods on the reproducibility of quantitative MRI of lower-limb muscles.
  
  
  METHODS
  Ten healthy subjects were scanned at 3 Tesla with a two-dimensional turbo spin-echo T1-weighted acquisition. Imaging was performed at thigh and calf level in two subject limb positions and independently repeated by a second operator. Regions-of-interest (ROI) were drawn on three muscles at thigh and calf levels on axial slices at fixed distance from the knee joint and at a level determined by surface anatomy.
  
  
  RESULTS
  Test-retest reliability of muscle cross-sectional area and ROI area overlap were similar for both limb positioning methods. Changing limb position between scans reduced ROI overlap (P < 0.01). Scout-image-based slice prescription resulted in narrower limits of agreement and higher intraclass correlation coefficients compared with surface-anatomy-based slice prescription.
  
  
  CONCLUSIONS
  Slice prescription based on fixed distance from the knee joint provided superior reproducibility of slice location than a surface anatomy-based method and should be used for longitudinal quantitative MRI studies. Exact subject positioning will depend on scanner and coil configuration, but should be consistent through a longitudinal study.
authors.affiliation: University of Basel Hospital, Department of Radiology, Division of Diagnostic and Interventional Neuroradiology, Basel, Switzerland; University of Basel Childrens Hospital, Basel, Switzerland; MRC Centre for Neuromuscular Diseases, Department of Molecular Neuroscience, UCL Institute of Neurology, London, United Kingdom.
authors.forename: Arne
authors.initials: A
authors.lastname: Fischmann
authors.forename: Jasper M
authors.initials: JM
authors.lastname: Morrow
authors.forename: Christopher D J
authors.initials: CD
authors.lastname: Sinclair
authors.forename: Mary M
authors.initials: MM
authors.lastname: Reilly
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hanna
authors.forename: Tarek
authors.initials: T
authors.lastname: Yousry
authors.forename: John S
authors.initials: JS
authors.lastname: Thornton
mesh_terms: D000328:Adult; D000465:Algorithms; D059925:Anatomic Landmarks / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D035002:Lower Extremity; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: magnetic resonance imaging (MRI); muscle; patient positioning; quantitative MRI; repeatability