Proton magnetic resonance relaxation behavior of whole muscle with fatty inclusions

This in vitro proton study of spin lattice (T1) and spin spin (T2) relaxation of muscle with storage-fat inclusions demonstrates slow exchange and lack of cross-relaxation between fat and water. Slow exchange causes biphasic T1 relaxation, but T2 relaxation is paradoxically uniphasic due to the nearly equal T2 values for both fractions. By careful dehydration and fat extraction, the relaxation information was deconvolved into water, fat, and protein contributions. The biphasic T1 decay has a short component due to lipid and a long component due to the water-protein combination. The fat content of muscle can be measured from the relative amplitude of the two T1 components or directly from the T2 relaxation time.