Change in the proton T(1) 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 contrast, 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.