Which nucleus from the common MR spectroscopy list is used to study cellular energy metabolism and is represented by the symbol Phosphorus?

• A. Sodium
• B. Oxygen
• C. Nitrogen
• D. Phosphorus

Answer: (D)

Understanding energy metabolism in MR spectroscopy hinges on detecting phosphate-containing compounds with the phosphorus nucleus. Phosphorus-31 MR spectroscopy can directly measure ATP, phosphocreatine, inorganic phosphate, and related phosphate metabolites, giving a direct readout of cellular energy state and intracellular pH. Because energy transfer in cells revolves around these phosphate bonds, phosphorus provides the most informative signal for this purpose.

Sodium-23, while useful for studying ion homeostasis and cell volume, does not directly report on the energy state of the cell. Nitrogen-15 and other nuclei have specialized or less direct applications for routine energy metabolism imaging. Therefore, the nucleus used to study cellular energy metabolism in MR spectroscopy is phosphorus-31, represented by phosphorus.