Quantitative ³¹P spectroscopic imaging of human brain at 4 Tesla: Assessment of gray and white matter differences of phosphocreatine and ATP

This report describes the implementation and application of a multicompartment analysis of ³¹P spectroscopic imaging data to determine the tissue-specific heterogeneities in metabolite content in the human brain and surrounding tissue. Using this information and a multicompartment regression analysis the phosphocreatine and ATP content of "pure" cerebral gray and white matter, the cerebellum, and skeletal muscle was determined in a group of 10 healthy volunteers. The data were converted to mM units using previously reported values for the T₁s of phosphocreatine and ATP at 4 T, the water content of human brain, and an external reference for absolute quantification. The phosphocreatine concentration in cerebral gray and white matter, the cerebellum, and skeletal muscle was 3.53 ± 0.33, 3.33 ± 0.37, 3.75 ± 0.66, and 25.8 ± 2.3 mM, respectively. The ATP concentration in cerebral gray and white matter, the cerebellum, and skeletal muscle was 2.19 ± 0.33, 3.41 ± 0.33, 1.75 ± 0.58, and 8.5 ± 1.9 mM, respectively.