In vivo T1 values of phosphorus metabolites in human liver and muscle determined at 1.5 T by chemical shift imaging.

A procedure for obtaining T1 values for phosphorous metabolites in localized regions of human subjects, using a standard 1.5 T MR imager, is described. 31P spectra and T1 values localized to the liver, and to abdominal and calf muscle of healthy volunteers were obtained by means of a multi-slice spectroscopy technique, consisting of a chemical shift imaging (CSI) sequence with a B1-insensitive excitation and one dimension of phase encoding, used in conjunction with a surface coil. An examination consisting of proton imaging, shimming and collection of 31P progressive saturation spectroscopic data for T1 determination required 1 h to perform. Shimming on the signal from the body region detected by the surface coil gave spectra of excellent spectral resolution. Quantification of all peaks in the localized 31P spectra was carried out with the PIQABLE algorithm, and T1 values were calculated for inorganic phosphate (Pi), the phosphodiester region, and the ATP alpha-, beta- and gamma peaks of liver, and for calf muscle Pi, phosphocreatine (PCr), and the three ATP peaks. The precisions of the measurement and of the entire process for obtaining and quantifying localized spectra by one-dimensional CSI were determined, and the accuracy of T1 values obtained by this means was verified. The temporal variation in T1 values obtained in a series of examinations of a single normal subject was also assessed. The consistency of the T1 values obtained in this study with in vivo T1 values obtained by other techniques is a stringent test of accuracy of localized spectra obtained with CSI.