Local diffusion and diffusion-T distribution measurements in porous media.

Slice-selective pulsed field gradient (PFG) and PFG-T measurements are developed to measure spatially-resolved molecular diffusion and diffusion-T distributions. A spatially selective adiabatic inversion pulse was employed for slice-selection. The slice-selective pulse is able to select a coarse slice, on the order of 1cm, at an arbitrary position in the sample. The new method can be employed to characterize oil-water mixtures in porous media. The new technique has an inherent sensitivity advantage over phase encoding imaging based methods due to signal being localized from a thick slice. The method will be advantageous for magnetic resonance of porous media at low field where sensitivity is problematic. Experimental CPMG data, following PFG diffusion measurement, were compromised by a transient ΔB(t) field offset. The off resonance effects of ΔB(t) were examined by simulation. The ΔB offset artifact in D-T distribution measurements may be avoided by employing real data, instead of magnitude data.