Diffusion of spins between physical or virtual, communicating compartments having different states of longitudinal magnetization leads to diffusion-driven longitudinal relaxation. Herein, in two model systems, the effects of diffusion-driven longitudinal relaxation are explored experimentally and analyzed quantitatively. In the first case, longitudinal relaxation in a single slice of a water phantom is monitored spectroscopically as a function of slice thickness. In the second case, mimicking vascular flow/diffusion effects, longitudinal relaxation is monitored in a two-compartment, semi-permeable fiber phantom. In both cases, apparent longitudinal relaxation, though clearly multi-exponential, is well-modeled as bi-exponential.

Original languageEnglish
Pages (from-to)30-36
Number of pages7
JournalJournal of Magnetic Resonance
Issue number1
StatePublished - Jul 2011


  • Flow
  • MRI
  • NMR
  • Semi-permeable fiber
  • Thin slice


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