Determination of saturation factors in 31P NMR spectra of the developing human brain

Abstract

In order to assess the influence of longitudinal relaxation on previously reported variations in ³¹P NMR signals during brain development, we used an accelerated two‐point technique to determine T¹ at 2.35 Tesla in 8 min. Comparison between 10 normal neonates (age range 37–46 weeks postconception) and 10 healthy infants (age range 80–157 weeks postconception) indicated that T¹ does not vary substantially during the first year of life, except in the phosphomonoester (PME) region of the spectra. T¹ 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 T¹ 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 T¹ below 2.9 s. Because the T¹ heterogeneity of PME may depend on its relative composition, quantitative ³¹P NMR spectroscopy may require an assessment of the influence of longitudinal relaxation on the signal amplitudes in each measurement.