CHAPTER 9: Multi-Quantum Filtered NMR and MRI of Cartilage

A study of cartilage using ¹H, ²H and ²³Na multiple quantum filtered nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques is presented. Double quantum filtered (DQF) spectra are best suited for the observation of the quadrupolar splittings, and enable determination of the orientation of the collagen fibers in this tissue. Measurements of the quadrupolar splittings at different orientations of the tissue relative to the magnetic field show that the collagen fibers are randomly oriented in nasal cartilage and macroscopically ordered in mature articular cartilage. Unidirectional mechanical stress and isotropic osmotic stress exert different effects on the orientation of the collagen fibers. Depletion of the proteoglycans preserves the orientation of the fibers. Gradual ordering of the collagen fibers in porcine articular cartilage during maturation is demonstrated. The ²³Na residual quadrupolar interaction in cartilage excised from osteoporotic human femoral heads is found to be considerably larger than that of controls. Proton DQF MRI was found to be useful in systems with large dipolar interactions, such as tendons.