Quantitation of phosphorus metabolites in newborn human brain using internal water as reference standard

A new method for noninvasive, in vivo quantitation of cerebral phosphorus (P-31) metabolites is described, The technique employs point-resolved spectroscopy (PRESS) to obtain both P-31-metabolite and proton (H-1) water spectra: brain water is used as an internal concentration reference. Spin-spin relaxation times (T(2)s) of cerebral P-31 metabolites are much longer than the minimum echo time (TE) usable on a spectrometer equipped with actively shielded gradient coils, With short-TE (similar to 10 ms) P-31 PRESS, T-2 relaxation is minimal and phase modulation of the nucleotide triphosphate (NTP) multiplets can be accounted for. H-1 water spectra were acquired using several TEs so that extra- and intracellular water signals could be separated from that due to cerebrospinal fluid, Prior calibration of the P-31 and H-1 spectrometer channels and an assumed brain-water concentration enabled estimations of metabolite concentrations, Using this method, mean P-31 metabolite concentrations in the brains of eight normal infants of gestational plus postnatal age 34 to 39 wk were: phosphomonoester (PME) 5.6 (SD 0.9); inorganic phosphate 1.4 (0.4); mobile phosphodiester 2.3 (0.6); phosphocreatine 2.9 (0.3); nucleotide triphosphate 2.8 (0.6); and total mobile phosphate 21.4 (2.8) mmol/kg wet.