Water in tendon: Orientational analysis of the free induction decay

Lada V. Krasnosselskaia, Gary D. Fullerton, Stephen J. Dodd, Ivan L. Cameron

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

The orientation dependence of the free induction decay (FID) of 1H NMR water signal in ex vivo bovine digital flexor tendon at the native level of hydration is reported. Residual dipolar coupling due to the overall tissue anisotropy produces a 6:1 change in the signal intensity as an angle between the long axis of a specimen and the external magnetic field is changed from the "magic angle" of 54.7° to 0°. The strength of residual dipolar interactions between water protons was estimated by orientational analysis of the signal intensity to be equal to 780 Hz. Apparent signal maxima are observed at orientations 8-13° away from 54.7° due to an inhomogeneous contribution to the decay. A small fraction of total water in tendon is detectable at all orientations and exhibits a shift in the precession frequency. It is hypothesized that this water fraction resides in the interconnecting gaps at the ends of collagen molecules. The gaps have a disordered environment that allows for a zero time average of dipolar interactions. Measured frequency and phase shifts are interpreted as signatures of the bulk magnetic susceptibility effect due to geometry of the cavity formed by adjacent gaps at the ends of the collagen molecules. The multiexponentiality of the FID decay is hypothesized to be due to the exchange between orientationally restricted water structured along the length of the collagen molecule and disordered water in the cavity.

Original languageEnglish (US)
Pages (from-to)280-288
Number of pages9
JournalMagnetic Resonance in Medicine
Volume54
Issue number2
DOIs
StatePublished - Aug 2005

Keywords

  • Anisotropy
  • Bulk magnetic susceptibility
  • Collagen
  • Free induction decay
  • Residual dipolar coupling
  • Tendon

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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