Continuous wave MRI of heterogeneous materials

Abstract

A prototype continuous wave MRI system operating at 7T has been used successfully to study a variety of heterogeneousmaterials exhibiting T2 relaxation values ranging from 10 ls to 50 ms. Two-dimensional images of a poly(methly methacrylate)(PMMA) resolution phantom (T2 ¼38 ls) exhibited a spatial resolution of approximately 1mm at a magneticfield gradient strengthof 200 mT/m. The technique was used to study the hydration, drying, and subsequent water penetration properties of cementsamples made from ordinary Portland cement, and revealed inhomogeneities arising from the cure conditions. Sandstone samplesfrom an oil reservoir in the North Sea were also studied; structure within these materials, arising from the sedimentary bed layeringin the reservoir, was found to have an effect on their water transport properties. A section from a confectionery bar (T2 approximately50–60 ms) was also imaged, and its internal structure could be clearly discerned.