Localized proton MR spectroscopy of the human kidney in vivo by means of short echo time STEAM sequences.

In order to obtain proton magnetic resonance spectra from the normal human kidney in vivo, we employed a STEAM sequence with delay times TE = 10 ms and TM = 30 ms. Signals are attenuated during STEAM sequences by J-coupling effects and by macroscopic movement of the sample. The combination of short echo times and respiratory triggering ensured that the kidney was stationary during the pulse sequence, and allowed us to detect strongly coupled resonances between 3 and 4.2 ppm. Analysis of spectra of extracts of bovine kidneys suggested that the renal MR-visible metabolites could include the osmolytes betaine, myo-inositol, and glycerophosphocholine. Four volunteers were subjected to overnight dehydration followed by rehydration, and we found that these signals increased significantly after dehydration, and decreased significantly 4 h after rehydration, thus supporting the assignment of the resonances as osmotically active metabolites.