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Local diffusion and diffusion-T2 distribution measurements in porous media
S Vashaee1, B Newling1, B MacMillan1
1UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|April 8, 2017
Summary
New magnetic resonance techniques enable spatially resolved measurements of molecular diffusion and diffusion-T2 distributions. This method offers improved sensitivity for characterizing porous media, especially at low magnetic fields.
Area of Science:
- Magnetic Resonance Imaging
- Materials Science
Background:
- Characterizing porous media is crucial for understanding fluid flow and storage.
- Spatially resolved diffusion measurements are essential for detailed analysis of complex materials.
- Low-field magnetic resonance faces sensitivity challenges for conventional imaging methods.
Purpose of the Study:
- To develop novel slice-selective pulsed field gradient (PFG) and PFG-T2 measurement techniques.
- To enable spatially resolved molecular diffusion and diffusion-T2 distribution measurements.
- To enhance the characterization of oil-water mixtures in porous media, particularly at low magnetic fields.
Main Methods:
- Employed a spatially selective adiabatic inversion pulse for slice selection, defining a coarse slice (approx. 1cm).
- Developed slice-selective pulsed field gradient (PFG) and PFG-T2 measurement sequences.
- Utilized simulations to examine off-resonance effects of transient field offsets (ΔB0(t)).
Main Results:
- Successfully measured spatially-resolved molecular diffusion and diffusion-T2 distributions.
- Demonstrated inherent sensitivity advantage over phase-encoding imaging methods due to signal localization from a thick slice.
- Identified that using real data instead of magnitude data can avoid ΔB0 offset artifacts in D-T2 distribution measurements.
Conclusions:
- The developed slice-selective PFG and PFG-T2 methods provide a sensitive approach for porous media analysis.
- The technique is particularly advantageous for low-field magnetic resonance applications where sensitivity is limited.
- Future work should focus on mitigating artifacts like ΔB0(t) for more accurate D-T2 distribution measurements.
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