title: Quantitative OCT and MRI biomarkers for the differentiation of cartilage degeneration.
abstract: OBJECTIVE
  To evaluate the usefulness of quantitative parameters obtained by optical coherence tomography (OCT) and magnetic resonance imaging (MRI) in the comprehensive assessment of human articular cartilage degeneration.
  
  
  METHODS
  Human osteochondral samples of variable degeneration (n = 45) were obtained from total knee replacements and assessed by MRI sequences measuring T1, T1ρ, T2 and T2* relaxivity and by OCT-based quantification of irregularity (OII, optical irregularity index), homogeneity (OHI, optical homogeneity index]) and attenuation (OAI, optical attenuation index]). Samples were also assessed macroscopically (Outerbridge classification) and histologically (Mankin classification) as grade-0 (Mankin scores 0-4)/grade-I (scores 5-8)/grade-II (scores 9-10)/grade-III (score 11-14). After data normalisation, differences between Mankin grades and correlations between imaging parameters were assessed using ANOVA and Tukey's post-hoc test and Spearman's correlation coefficients, respectively. Sensitivities and specificities in the detection of Mankin grade-0 were calculated.
  
  
  RESULTS
  Significant degeneration-related increases were found for T2 and OII and decreases for OAI, while T1, T1ρ, T2* or OHI did not reveal significant changes in relation to degeneration. A number of significant correlations between imaging parameters and histological (sub)scores were found, in particular for T2 and OII. Sensitivities and specificities in the detection of Mankin grade-0 were highest for OHI/T1 and OII/T1ρ, respectively.
  
  
  CONCLUSIONS
  Quantitative OCT and MRI techniques seem to complement each other in the comprehensive assessment of cartilage degeneration. Sufficiently large structural and compositional changes in the extracellular matrix may thus be parameterized and quantified, while the detection of early degeneration remains challenging.
authors.affiliation: Department of Orthopaedics, Aachen University Hospital, Pauwelsstr. 30, 52074, Aachen, Germany. snebelung@ukaachen.de.|Institute of Anatomy and Cell Biology, RWTH, Aachen, Germany. snebelung@ukaachen.de.
authors.forename: Sven
authors.initials: S
authors.lastname: Nebelung
authors.affiliation: Fraunhofer Institute for Production Technology, Aachen, Germany.
authors.forename: Nicolai
authors.initials: N
authors.lastname: Brill
authors.affiliation: Department of Orthopaedics, Aachen University Hospital, Pauwelsstr. 30, 52074, Aachen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Tingart
authors.affiliation: Institute of Anatomy and Cell Biology, RWTH, Aachen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pufe
authors.affiliation: Department of Diagnostic and Interventional Radiology, Aachen University Hospital, Aachen, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Kuhl
authors.affiliation: Department of Orthopaedics, Aachen University Hospital, Pauwelsstr. 30, 52074, Aachen, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Jahr
authors.affiliation: Department of Diagnostic and Interventional Radiology, Aachen University Hospital, Aachen, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Truhn
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D015415:Biomarkers / Q000032:analysis*; D002357:Cartilage Diseases / Q000145:classification / Q000473:pathology*; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000379:methods*
chemical_list: D015415:Biomarkers
keywords: Cartilage; MRI; OCT; Osteoarthritis; Parameterization; Quantification