Multicomponent T-2 relaxation of in vivo skeletal muscle

In vivo spin-spin (T-2) relaxation measurements were acquired from the flex or digitorum profundus (FDP) of 13 subjects. A standard imaging T2 measurem ent technique [number of points (N) = 6, TE = 18 msec, signal-to-noise rati o (SNR) congruent to 300] yielded a single T-2 value of 31 msec. A novel te chnique, projection presaturation combined with a CPMG sequence, was used t o acquire data (N = 1000, TE = 1.2 msec, SNR 3500) from a cylindrical voxel (2 cm diameter, 5 cm length) within the FDP. All 13 subjects had at least four T2 components, at <5, 21 +/- 4, 39 +/- 6, and 114 +/- 31 msec, with fr actional areas of 11 +/- 2, 28 +/- 15, 46 +/- 12, and 11 +/- 5% respectivel y. The shortest and longest components have been observed in ex vivo muscle studies, probably corresponding to water associated with macromolecules an d extracellular water, respectively. The middle T-2 components are suggesti ve of an organization of in vivo intracellular water. Magn Reson Med 42:150 -157, 1999. (C) 1999 Wiley-Liss, Inc.