Magnetic Field Dependence of Spectral Correlations between 31 P-Containing Metabolites in Brain.

Spectral correlations between metabolites in P magnetic resonance spectroscopy (MRS) spectra of human brain were compared at 3 and 7 Tesla, the two commonly used magnetic field strengths for clinical research. It was found that at both field strengths, there are significant correlations between P-containing metabolites arising from spectral overlap, and their downfield correlations are markedly altered by the background spectral baseline. Overall, the spectral correlations between P-containing metabolites are markedly reduced at 7 Tesla with the increased chemical shift dispersion and the decreased membrane phospholipid signal. The findings provide the quantitative landscape of pre-existing correlations in P MRS spectra due to overlapping signals. Detailed procedures for quantifying the pre-existing correlations between P-containing metabolites are presented to facilitate incorporation of spectral correlations into statistical modeling in clinical correlation studies.