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. Author manuscript; available in PMC: 2015 Apr 1.
Published in final edited form as: Neuroimage. 2013 Dec 15;89:92–109. doi: 10.1016/j.neuroimage.2013.12.007

Figure 2.

Figure 2

Two site exchange (2SX) model depicting the pool of free water and pool of water bound to macromolecules. In each pool water molecules experience dipolar coupling relaxation governed by the correlation times τc of each pool. The two pools are considered in an equilibrium anisochronous exchange determined by the exchange time τex and the chemical shift difference δωex. The model is specified by four independent parameters: correlation time τc,b of bound water, τex, δωex and bound water fraction Pb (Pf = 1− Pb and τc,f ≈ 5 ps). The fast exchange limit (FXL) it is assumed in-vivo δωexτex ≪ 1.