1H NMR relaxation measurements of human tissues in situ by spatially resolved spectroscopy.

Spatially resolved spectroscopy (SPARS) is a method for obtaining high-resolution NMR spectra of well-defined volumes of human tissues in situ. This method was combined with the Carr-Purcell-Meiboom-Gill multiple-echo sequence for T2, and with inversion recovery for T1 relaxation measurements. Relaxation times obtained by SPARS were compared with standard CPMG and IR relaxation measurements and with imaging methods, using a number of relaxation phantoms. Spectroscopically resolved relaxation data of human bone marrow, muscle, and adipose tissue in situ were obtained. T2 measurements of human adipose tissue gave different results when using single-echo measurements rather than the CPMG method. This difference was interpreted as a J modulation effect, which shows up in fatty acid proton resonances. This J modulation effect influences the intensity of adipose tissue in routine 1H NMR images.