A signature of non-Gaussian diffusion in porous systems

Diffusion is ubiquitous in porous systems and NMR may provide essential information about the underlying complex microstructure non-invasively. However, the interpretation of the NMR signal and its connection to the presence of non-Gaussian footprints or several Gaussian compartments is intricate. This work reports on novel methodology that utilizes a symmetric-double Pulse Field Gradient (PFG) technique to distinguish the two different contributions by measuring the fourth cumulant (Kurtosis) of diffusion and its origins.

Figure 1 highlights the signal oscillations of water diffusing in a Glass Capillary Array (GCA). The four oscillations in the signal is a footprint of non-Gaussian diffusion. In addition, it is apparent that higher q values contribute to the sensitivity of observing the signal modulations. 

References:  Paulsen, J. L., Özarslan, E., Komlosh, M. E., Basser, P. J., & Song, Y. Q. (2015). Detecting compartmental non‐Gaussian diffusion with symmetrized double‐PFG MRI. NMR in Biomedicine, 28(11), 1550-1556. https://doi.org/10.1002/nbm.3363