title: Spin-lattice relaxation rates and water content of freeze-dried articular cartilage.
abstract: 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.
authors.affiliation: School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: R A
authors.initials: RA
authors.lastname: Damion
authors.forename: S S
authors.initials: SS
authors.lastname: Pawaskar
authors.forename: M E
authors.initials: ME
authors.lastname: Ries
authors.forename: E
authors.initials: E
authors.lastname: Ingham
authors.forename: S
authors.initials: S
authors.lastname: Williams
authors.forename: Z
authors.initials: Z
authors.lastname: Jin
authors.forename: A
authors.initials: A
authors.lastname: Radjenovic
mesh_terms: D000818:Animals; D001834:Body Water; D002358:Cartilage, Articular / Q000737:chemistry*; D002417:Cattle / Q000378:metabolism*; D005612:Freeze Drying / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008954:Models, Biological; D013045:Species Specificity; D034421:Sus scrofa / Q000378:metabolism*