Maps of Self-Diffusion Coefficients by Radiofrequency Field Gradient NMR Microscopy

Abstract

The methods of measurement of spatially resolved diffusion coefficients using radiofrequency field gradient (E. Mischler et al., J. Magn. Reson. B 106, 32, 1995; R. Kimmich et al., J. Magn. Reson. A 112, 7, 1995) produce 1D profiles whose amplitude is not only a function of the local self-diffusion coefficient but also is modulated by cosine functions of spatial coordinates. Due to this modulation diffusion-weighted images cannot be obtained unless cumbersome data processing is used. Here, we present a new sequence which avoids this modulation and yields in a straightforward manner true self-diffusion coefficient maps; this is in contrast with conventional methods which use static field gradients and which are therefore altered by background gradients. The feasibility and the reliability of the method are demonstrated with phantoms; it is also applied to different systems of interest such as solvent swelled rubber, membranes, and plants.