title: Dependence of light attenuation and backscattering on collagen concentration and chondrocyte density in agarose scaffolds.
abstract: Optical coherence tomography (OCT) has been applied for high resolution imaging of articular cartilage. However, the contribution of individual structural elements of cartilage on OCT signal has not been thoroughly studied. We hypothesize that both collagen and chondrocytes, essential structural components of cartilage, act as important light scatterers and that variation in their concentrations can be detected by OCT through changes in backscattering and attenuation. To evaluate this hypothesis, we established a controlled model system using agarose scaffolds embedded with variable collagen concentrations and chondrocyte densities. Using OCT, we measured the backscattering coefficient (µb) and total attenuation coefficient (µt) in these scaffolds. Along our hypothesis, light backscattering and attenuation in agarose were dependent on collagen concentration and chondrocyte density. Significant correlations were found between µt and chondrocyte density (ρ = 0.853, p < 0.001) and between µt and collagen concentration (ρ = 0.694, p < 0.001). µb correlated significantly with chondrocyte density (ρ = 0.504, p < 0.001) but not with collagen concentration (ρ = 0.103, p = 0.422) of the scaffold. Thus, quantitation of light backscattering and, especially, attenuation could be valuable when evaluating the integrity of soft tissues, such as articular cartilage with OCT.
authors.affiliation: Department of Applied Physics, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland. Department of Clinical Neurophysiology, Kuopio University Hospital, PO Box 1777, FI-70029 Kuopio, Finland.
authors.forename: P H
authors.initials: PH
authors.lastname: Puhakka
authors.forename: J H
authors.initials: JH
authors.lastname: Ylärinne
authors.forename: M J
authors.initials: MJ
authors.lastname: Lammi
authors.forename: S
authors.initials: S
authors.lastname: Saarakkala
authors.forename: V
authors.initials: V
authors.lastname: Tiitu
authors.forename: H
authors.initials: H
authors.lastname: Kröger
authors.forename: T
authors.initials: T
authors.lastname: Virén
authors.forename: J S
authors.initials: JS
authors.lastname: Jurvelin
authors.forename: J
authors.initials: J
authors.lastname: Töyräs
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology* / Q000528:radiation effects; D002417:Cattle; D019902:Chondrocytes / Q000166:cytology* / Q000528:radiation effects; D003094:Collagen / Q000378:metabolism* / Q000528:radiation effects; D003720:Densitometry; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008027:Light; D012542:Scattering, Radiation; D012685:Sepharose / Q000378:metabolism* / Q000528:radiation effects; D041623:Tomography, Optical Coherence / Q000379:methods*
chemical_list: D003094:Collagen; D012685:Sepharose