Change in the Proton T1 of Fat and Water in Mixture

This work describes observed changes in the proton T-1 relaxation time of both water and lipid when they are in relatively homogeneous mixtures. Results obtained from vegetable oil-water emulsions, pork kidney and lard mixtures, and excised samples of white and brown adipose tissues are presented to demonstrate this change in T-1 as a function of mixture fat fraction. As an initial proof of concept, a simpler acetone-water experiment was performed to take advantage of complete miscibility between acetone and water and both components' single chemical shift peaks. Single-voxel MR spectroscopy was used to measure the T-1 of predominant methylene spins in fat and the T-1 of water spins in each setup. In the vegetable oil-water emulsions, the T-1 of fat varied by as much as 3-fold when water was the dominant mixture component. The T-1 of pure lard increased by 170 msec (+37%) when it was blended with lean kidney tissue in a 16% fatty mixture. The fat T-1 of lipid-rich white adipose tissue was 312 msec. In contras, the fat T-1 of leaner brown adipose tissue (fat fraction 53%) was 460 msec. A change in the water T-1 from that of pure water was also observed in the experiments. Magn Reson Med 63:494-501, 2010. (C) 2009 Wiley-Liss, Inc.