title: Optical spectral imaging of degeneration of articular cartilage.
abstract: Osteoarthritis (OA) is a common musculoskeletal disorder often diagnosed during arthroscopy. In OA, visual color changes of the articular cartilage surface are typically observed. We demonstrate in vitro the potential of visible light spectral imaging (420 to 720 nm) to quantificate these color changes. Intact bovine articular cartilage samples (n=26) are degraded both enzymatically using the collagenase and mechanically using the emery paper (P60 grit, 269 microm particle size). Spectral images are analyzed by using standard CIELAB color coordinates and the principal component analysis (PCA). After collagenase digestion, changes in the CIELAB coordinates and projection of the spectra to PCA eigenvector are statistically significant (p<0.05). After mechanical degradation, the grinding tracks could not be visualized in the RGB presentation, i.e., in the visual appearance of the sample to the naked eye under the D65 illumination. However, after projecting to the chosen eigenvector, the grinding tracks are revealed. The tracks are also seen by using only one wavelength, i.e., 469 nm, however, the contrast in the projection image is 1.6 to 2.5 times higher. Our results support the idea that the spectral imaging can be used for evaluation of the integrity of the cartilage surface.
authors.affiliation: University of Eastern Finland, Department of Physics and Mathematics, Joensuu, Finland. jussi.kinnunen@uef.fi
authors.forename: Jussi
authors.initials: J
authors.lastname: Kinnunen
authors.forename: Jukka S
authors.initials: JS
authors.lastname: Jurvelin
authors.forename: Jaana
authors.initials: J
authors.lastname: Mäkitalo
authors.forename: Markku
authors.initials: M
authors.lastname: Hauta-Kasari
authors.forename: Pasi
authors.initials: P
authors.lastname: Vahimaa
authors.forename: Simo
authors.initials: S
authors.lastname: Saarakkala
mesh_terms: D000465:Algorithms; D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology*; D002417:Cattle; D003124:Colorimetry / Q000379:methods*; D004195:Disease Models, Animal; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008029:Lighting / Q000379:methods*; D020370:Osteoarthritis, Knee; D010781:Photography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000379:methods*