Abstract
In order to assess the influence of longitudinal relaxation on previously reported variations in ^31^P NMR signals during brain development, we used an accelerated twoβpoint technique to determine T^1^ at 2.35 Tesla in 8 min. Comparison between 10 normal neonates (age range 37β46 weeks postconception) and 10 healthy infants (age range 80β157 weeks postconception) indicated that T^1^ does not vary substantially during the first year of life, except in the phosphomonoester (PME) region of the spectra. T^1^ of total PME decreases with age which we could explain by its variable multicomponent nature: The signal from (unresolved) components at the downfield shoulder of PME (attributed mostly to phosphorylethanolamine at 6.72 ppm) with a T^1^ of at least 6.4 s decreases with age relative to contributions from other phosphomonoester compounds resonating predominantly at the upfield side of the peak (approximately 6.3 ppm), with T^1^ below 2.9 s. Because the T^1^ heterogeneity of PME may depend on its relative composition, quantitative ^31^P NMR spectroscopy may require an assessment of the influence of longitudinal relaxation on the signal amplitudes in each measurement.