Continuous wave MRI of heterogeneous materials

A prototype continuous wave MRI system operating at 7 T has been used successfully to study a variety of heterogeneous materials exhibiting T-2 relaxation values ranging from 10 mus to 50 ms. Two-dimensional images of a poly(methly methacrylate) (PMMA) resolution phantom (T-2 = 38 mus) exhibited a spatial resolution of approximately 1 mm at a magnetic field gradient strength of 200 mT/m. The technique was used to study the hydration, drying, and subsequent water penetration properties of cement samples made from ordinary Portland cement, and revealed inhomogeneities arising from the cure conditions. Sandstone samples from an oil reservoir in the North Sea were also studied; structure within these materials, arising from the sedimentary bed layering in the reservoir, was found to have an effect on their water transport properties. A section from a confectionery bar (T-2* approximately 50-60 ms) was also imaged, and its internal structure could be clearly discerned. (C) 2003 Elsevier Science (USA). All rights reserved.