John David Dickson1, Guy Barnett Williams2,
  Thomas Adrian Carpenter2, Richard E. Ansorge1
1Department of Physics, Cambridge
  University, Cambridge, Cambridgeshire, United Kingdom; 2Wolfson
  Brain Imaging Centre, Cambridge University, Cambridge, Cambridgeshire, United
  Kingdom
It
  has been suggested that extracellular fluid spins undergo bulk dephasing from
  those in intracellular fluid. This study provides direct evidence for this
  phenomenon and exploits it to make quantitative measurements of both the
  intra/extracellular fluid volume fractions and precession frequencies. This
  is achieved by fitting the data from a Gradient Echo Sampling of a Free
  Induction Decay (GESFID) sequence with a complex signal model.
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