QUANTITATION OF PHOSPHORUS METABOLITES IN NEWBORN HUMAN BRAIN USING INTERNAL WATER AS REFERENCE-STANDARD

A new method for noninvasive, in vivo quantitation of cerebral phospho rus (P-31) metabolites is described, The technique employs point-resol ved spectroscopy (PRESS) to obtain both P-31-metabolite and proton (H- 1) water spectra: brain water is used as an internal concentration ref erence. Spin-spin relaxation times (T(2)s) of cerebral P-31 metabolite s are much longer than the minimum echo time (TE) usable on a spectrom eter equipped with actively shielded gradient coils, With short-TE (si milar to 10 ms) P-31 PRESS, T-2 relaxation is minimal and phase modula tion 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 ce rebrospinal 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 pl us 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); phos phocreatine 2.9 (0.3); nucleotide triphosphate 2.8 (0.6); and total mo bile phosphate 21.4 (2.8) mmol/kg wet.