title: Automated segmentation and analysis of normal and osteoarthritic knee menisci from magnetic resonance images--data from the Osteoarthritis Initiative.
abstract: OBJECTIVE
  To validate an automatic scheme for the segmentation and quantitative analysis of the medial meniscus (MM) and lateral meniscus (LM) in magnetic resonance (MR) images of the knee.
  
  
  METHODS
  We analysed sagittal water-excited double-echo steady-state MR images of the knee from a subset of the Osteoarthritis Initiative (OAI) cohort. The MM and LM were automatically segmented in the MR images based on a deformable model approach. Quantitative parameters including volume, subluxation and tibial-coverage were automatically calculated for comparison (Wilcoxon tests) between knees with variable radiographic osteoarthritis (rOA), medial and lateral joint space narrowing (mJSN, lJSN) and pain. Automatic segmentations and estimated parameters were evaluated for accuracy using manual delineations of the menisci in 88 pathological knee MR examinations at baseline and 12 months time-points.
  
  
  RESULTS
  The median (95% confidence-interval (CI)) Dice similarity index (DSI) (2 ∗|Auto ∩ Manual|/(|Auto|+|Manual|)∗ 100) between manual and automated segmentations for the MM and LM volumes were 78.3% (75.0-78.7), 83.9% (82.1-83.9) at baseline and 75.3% (72.8-76.9), 83.0% (81.6-83.5) at 12 months. Pearson coefficients between automatic and manual segmentation parameters ranged from r = 0.70 to r = 0.92. MM in rOA/mJSN knees had significantly greater subluxation and smaller tibial-coverage than no-rOA/no-mJSN knees. LM in rOA knees had significantly greater volumes and tibial-coverage than no-rOA knees.
  
  
  CONCLUSIONS
  Our automated method successfully segmented the menisci in normal and osteoarthritic knee MR images and detected meaningful morphological differences with respect to rOA and joint space narrowing (JSN). Our approach will facilitate analyses of the menisci in prospective MR cohorts such as the OAI for investigations into pathophysiological changes occurring in early osteoarthritis (OA) development.
authors.affiliation: The Australian e-Health Research Centre, CSIRO Computational Informatics, Royal Brisbane and Women's Hospital, Herston, QLD 4029, Australia; School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4027, Australia. Electronic address: anthony.paproki@uqconnect.edu.au.
authors.forename: A
authors.initials: A
authors.lastname: Paproki
authors.affiliation: School of Human Movement Studies, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address: c.engstrom@uq.edu.au.
authors.forename: C
authors.initials: C
authors.lastname: Engstrom
authors.affiliation: The Australian e-Health Research Centre, CSIRO Computational Informatics, Royal Brisbane and Women's Hospital, Herston, QLD 4029, Australia. Electronic address: shekhar.chandra@uq.edu.au.
authors.forename: S S
authors.initials: SS
authors.lastname: Chandra
authors.affiliation: The Australian e-Health Research Centre, CSIRO Computational Informatics, Royal Brisbane and Women's Hospital, Herston, QLD 4029, Australia; School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4027, Australia. Electronic address: ales.neubert@uqconnect.edu.au.
authors.forename: A
authors.initials: A
authors.lastname: Neubert
authors.affiliation: The Australian e-Health Research Centre, CSIRO Computational Informatics, Royal Brisbane and Women's Hospital, Herston, QLD 4029, Australia. Electronic address: jurgen.fripp@csiro.au.
authors.forename: J
authors.initials: J
authors.lastname: Fripp
authors.affiliation: School of Information Technology and Electrical Engineering, The University of Queensland, St Lucia, QLD 4027, Australia. Electronic address: stuart@itee.uq.edu.au.
authors.forename: S
authors.initials: S
authors.lastname: Crozier
mesh_terms: D000368:Aged; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D005269:Femur / Q000473:pathology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology*; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*; D015203:Reproducibility of Results; D013977:Tibia / Q000473:pathology
keywords: Automated segmentation; Lateral meniscus; MRI; Medial meniscus; Morphometric analysis; Osteoarthritis