Magnetic resonance imaging studies of the behavior of fluids in gelatin and other porous materials

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Antalek, Brian J.
Magnetic resonance imaging
thesis / dissertation description
An application of magnetic resonance imaging to the study of the diffusion of water in gelatin and other materials is described. Gelatin was studied in great detail while plaster, balsa wood, and cement were studied to a lesser degree. Images of the materials at various stages of the diffusion process were recorded and analyzed. In order to properly interpret the imaging signal, the relationships between two intrinsic system parameters, Ti and T2, with the experimental parameters of the study need to be established. In the case of gelatin studies, Ti and T2 times were measured for gelatin samples varying in gelatin concentration and degree of D20 dilution. Tx and T2 were found to decrease with increasing gelatin concentration and increase with increasing D 20 dilution. T 1 relationships were modeled successfully with the crossrelaxation theory while T2 relationships were established empirically. Two gelatin studies were performed, one involving the counterdiffusion of H20 and D20 in a crosslinked gelatin matrix of a given gelatin concentration, and one involving the drying of a water containing gelatin matrix. In the counter-diffusion study, the selfdiffusion coefficient for H20 was found to be 2.0 x 10~5 cm2/s. The diffusion coefficients of H20 in gelatin matricies of 1.5, 5, and 11% wt. gelatin were found to be 2.0, 1.8, and 1.5 x 10-5 cm2/s, respectfully. In the drying study, it was found that a good first approximation for the modeling of the drying process is provided by Fick's second equation solved with a diffusion coefficient depending linearly with gelatin concentration. The shrinking character of the drying gelatin sample needs to be included in a more precise model.