Static dephasing regime

Fig. 11. Computer-generated data for spheres with a volumic fraction v = 5 x 10 and Ad) = 2.64 x 10 rad/s, plotted vs. TD.The open symbols represent I/T2 value, while the filled symbols represent rates obtained, respectively, with tcp = 0.1 ms ( , and line a), 0.2 ms ( , and line b), 0.5 ms ( , and line c), 2 ms (T, and line d), 5 ms (A, and line e), 10 ms ( , and line f), 20 ms ( , and line g). The short dashed line is the rate predicted by outer sphere theory and the long dashed line is the Static Dephasing Regime model from 22). Lines (a-g) are the rates given by Eq. (11).

Without spin refocusing, the simulations show that R2 reaches a plateau for diameters above 0.02 pm. The corresponding maximum relaxation rate of about 100 s is predicted by the Static Dephasing Regime (SDR) model 22, 23), which assumes that, as depicted above, transverse relaxation is only attributed to differences in precession frequencies of static spins. The relaxation rate is then given by ... 

The so-called static dephasing regime (SDR) predicts a linear dependence of I/T2 on the magnetic moment of the particles in solution (22, 25). This regime describes the transverse relaxation of homogeneously distributed static protons in the presence of static, randomly distributed point dipoles. The free induction decay rate, I/T2, is then proportional to the part of the sample magnetization due to the dipoles (p), M = rap, where ra is the concentration... 

Yablonskiy, D. A. Haacke, E. M. Theory of NMR signal behavior in magnetically inhomogeneous tissues the static dephasing regime. 

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