title: Low-field one-dimensional and direction-dependent relaxation imaging of bovine articular cartilage.
abstract: The structure of articular cartilage is separated into three layers of differently oriented collagen fibers, which is accompanied by a gradient of increasing glycosaminoglycan (GAG) and decreasing water concentration from the top layer towards the bone interface. The combined effect of these structural variations results in a change of the longitudinal and transverse relaxation times as a function of the distance from the cartilage surface. In this paper, this dependence is investigated at a magnetic field strength of 0.27 T with a one-dimensional depth resolution of 50 μm on bovine hip and stifle joint articular cartilage. By employing this method, advantage is taken of the increasing contrast of the longitudinal relaxation rate found at lower magnetic field strengths. Furthermore, evidence for an orientational dependence of relaxation times with respect to an axis normal to the surface plane is given, an observation that has recently been reported using high-field MRI and that was explained by preferential orientations of collagen bundles in each of the three cartilage zones. In order to quantify the extent of a further contrast mechanism and to estimate spatially dependent glycosaminoglycan concentrations, the data are supplemented by proton relaxation times that were acquired in bovine articular cartilage that was soaked in a 0.8 mM aqueous Gd++ solution.
authors.affiliation: Fachgebiet Technische Physik II/Polymerphysik, Institute of Physics, Technische Universität Ilmenau, PO Box 100 565, 98684 Ilmenau, Germany.
authors.forename: Erik
authors.initials: E
authors.lastname: Rössler
authors.forename: Carlos
authors.initials: C
authors.lastname: Mattea
authors.forename: Ayret
authors.initials: A
authors.lastname: Mollova
authors.forename: Siegfried
authors.initials: S
authors.lastname: Stapf
mesh_terms: D000465:Algorithms; D000818:Animals; D016880:Anisotropy; D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000737:chemistry; D002417:Cattle; D003094:Collagen / Q000737:chemistry; D003287:Contrast Media; D004574:Electromagnetic Fields; D005240:Feasibility Studies; D005269:Femur / Q000033:anatomy & histology; D019786:Gadolinium DTPA; D006025:Glycosaminoglycans / Q000737:chemistry; D007596:Joints / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D009584:Nitrogen / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; D014867:Water; D003094:Collagen; D019786:Gadolinium DTPA; D009584:Nitrogen