Dmitry S. Novikov1, Valerij G. Kiselev2
Diffusion coefficient is known to reveal the surface-to-volume ratio of restrictions at short diffusion times. Sufficiently short diffusion times are practically achievable with the oscillating gradient technique or with the CPMG refocusing train in the presence of a static gradient. Interpetation of such measurements relies on representing the short-time diffusivity limit in the frequency domain. For both of these oscillating techniques, we derive exact expressions for the high-frequency behavior of the diffusion coefficient, applicable to probe the surface-to-volume ratio of restrictions. We also describe how to calculate the effect of restrictions for arbitrary gradient waveforms.