Non-invasive quantitation of human liver metabolites using image-guided 31P magnetic resonance spectroscopy.

Phosphorus-containing metabolites in normal human liver have been quantitated non-invasively with 31P magnetic resonance spectroscopy using surface coils. The location of the volume of interest (VOI) was defined by 1H magnetic resonance imaging. Subsequently, a modified three-dimensional localization technique (ISIS) was used to acquire 31P magnetic resonance spectra from the VOI. To account for partial saturation produced by rapid signal averaging, the spin/lattice relaxation times (T1) of all hepatic phosphorus resonances were measured. The corrected resonance integrals were used to derive absolute molar concentrations for the following hepatic metabolites (mmol/kg wet weight): ATP, 2.0; inorganic phosphate, 2.1; phosphodiesters, 5.4; and phosphomonoesters, 0.9. These values are compared with previously reported values for humans using freeze-clamping techniques, and provide a basis for comparison with studies of hepatic disease in this laboratory.