Imaging of nuclear magnetic resonance spin–lattice relaxation activation energy in cartilage

Samples of human and bovine cartilage have been examined using magnetic resonance imaging to determine the proton nuclear magnetic resonance spin–lattice relaxation time, T1, as a function of depth within through the cartilage tissue. T1 was measured at five to seven temperatures between 8 and 38°C. From this, it is shown that the T1 relaxation time is well described by Arrhenius-type behaviour and the activation energy of the relaxation process is quantified. The activation energy within the cartilage is approximately 11 ± 2 kJ mol−1 with this notably being less than that for both pure water (16.6 ± 0.4 kJ mol−1) and the phosphate-buffered solution in which the cartilage was immersed (14.7 ± 1.0 kJ mol−1). It is shown that this activation energy increases as a function of depth in the cartilage. It is known that cartilage composition varies with depth, and hence, these results have been interpreted in terms of the structure within the cartilage tissue and the association of the water with the macromolecular constituents of the cartilage

In vivo diffusion measurements of the finger by nuclear magnetic resonance imaging

SIGLEAvailable from British Library Document Supply Centre- DSC:DX176573 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Spin-lattice relaxation rates and water content of freeze-dried articular cartilage.

Objective: Nuclear magnetic resonance (NMR) spin-lattice relaxation rates were measured in bovine and porcine articular cartilage as a function of water content. Methods: Water content was varied by freeze-drying samples for short periods of time (up to 15. min). The samples were weighed at all stages of drying so that water content could be quantified. Spin-lattice relaxation rates were measured using magnetic resonance imaging (MRI). Results: Linear correlations were observed between relaxation rate and two measures of inverse water content: (1) solid-to-water ratio (ρ), expressed as a ratio of the mass of the solid component of the cartilage (m s) and the mass of water at each freeze-drying time point (m w), and (2) a ratio of the total mass of the fully-hydrated cartilage and m w (1/w). These correlations did not appear significantly different for the bovine and porcine data. However, fitting the data to a piecewise-linear model revealed differences between these two species. We interpret the first two segments of the piecewise model as the depletion of different water phases but conjecture that the third segment is partially caused by changes in relaxation rates as a result of a reduction in macromolecular mobilities. Conclusions: Whilst we can produce linear correlations which broadly describe the dependence of the measured spin-lattice relaxation rate on (inverse) water content, the linear model seems to obscure a more complicated relationship which potentially provides us with more information about the structure of articular cartilage and its extracellular water