title: Articular cartilage degeneration classification by means of high-frequency ultrasound.
abstract: BACKGROUND
  To date only single ultrasound parameters were regarded in statistical analyses to characterize osteoarthritic changes in articular cartilage and the potential benefit of using parameter combinations for characterization remains unclear.
  
  
  OBJECTIVE
  Therefore, the aim of this work was to utilize feature selection and classification of a Mankin subset score (i.e., cartilage surface and cell sub-scores) using ultrasound-based parameter pairs and investigate both classification accuracy and the sensitivity towards different degeneration stages.
  
  
  METHODS
  40 punch biopsies of human cartilage were previously scanned ex vivo with a 40-MHz transducer. Ultrasound-based surface parameters, as well as backscatter and envelope statistics parameters were available. Logistic regression was performed with each unique US parameter pair as predictor and different degeneration stages as response variables. The best ultrasound-based parameter pair for each Mankin subset score value was assessed by highest classification accuracy and utilized in receiver operating characteristics (ROC) analysis.
  
  
  RESULTS
  The classifications discriminating between early degenerations yielded area under the ROC curve (AUC) values of 0.94-0.99 (mean ± SD: 0.97 ± 0.03). In contrast, classifications among higher Mankin subset scores resulted in lower AUC values: 0.75-0.91 (mean ± SD: 0.84 ± 0.08). Variable sensitivities of the different ultrasound features were observed with respect to different degeneration stages.
  
  
  CONCLUSIONS
  Our results strongly suggest that combinations of high-frequency ultrasound-based parameters exhibit potential to characterize different, particularly very early, degeneration stages of hyaline cartilage. Variable sensitivities towards different degeneration stages suggest that a concurrent estimation of multiple ultrasound-based parameters is diagnostically valuable. In-vivo application of the present findings is conceivable in both minimally invasive arthroscopic ultrasound and high-frequency transcutaneous ultrasound.
authors.affiliation: Julius Wolff Institute and Berlin-Brandenburg School for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Männicke
authors.affiliation: Julius Wolff Institute and Berlin-Brandenburg School for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schöne
authors.affiliation: Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: M
authors.initials: M
authors.lastname: Oelze
authors.affiliation: Julius Wolff Institute and Berlin-Brandenburg School for Regenerative Therapies, Charité-Universitätsmedizin Berlin, Germany. Electronic address: kay.raum@charite.de.
authors.forename: K
authors.initials: K
authors.lastname: Raum
mesh_terms: D002357:Cartilage Diseases / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology; D016022:Case-Control Studies; D006801:Humans; D016015:Logistic Models; D020370:Osteoarthritis, Knee / Q000150:complications / Q000000981:diagnostic imaging*; D012372:ROC Curve; D014463:Ultrasonography
keywords: Backscatter; Cartilage; Classification; Degeneration; Osteoarthrosis; Ultrasound biomicroscopy