Clinical applications of ³¹P-MRS and ²³Na-MRI in the upper abdomen

Multinuclear magnetic resonance imaging (MRI), which uses nuclei other than protons (¹H), has undergone a dramatic transformation with the advent of regulatory-approved radiofrequency coils. Phosphorus-31 magnetic resonance spectroscopy (³¹P-MRS) and sodium-23 MRI (²³Na-MRI) are now accessible at clinical sites equipped with commercially available surface coils, enabling advanced metabolic and tissue characterization without specialized research infrastructure or ultra-high-field systems. ³¹P-MRS provides a quantitative assessment of cellular energy metabolism and mitochondrial function while enabling the calculation of the intracellular pH. ²³Na-MRI visualizes the in vivo distribution of sodium, which is relevant since sodium ion distribution plays a critical role in cellular function and ionic homeostasis. Sodium concentration serves as an important biomarker of tissue health status. Both ³¹P-MRS and ²³Na-MRI have been widely utilized to assess multiple organ systems as well as diseases of the brain, heart, skeletal muscle, and tumors. However, clinical implementation using newly approved coils remains largely undefined, as the optimal acquisition protocols, target organ selection, coil positioning, interpretation criteria, and disease-specific imaging strategies have not been established. This review synthesized technical considerations for surface coil-based upper abdominal imaging, methodological approaches, and preliminary clinical findings from our initial clinical experience with ³¹P-MRS and ²³Na-MRI.