Rapid and simultaneous measurement of phosphorus metabolite pool size ratio and reaction kinetics of enzymes in vivo.

The metabolites phosphocreatine (PCr), adenosine triphosphate (ATP), and in-organic phosphate (Pi) are biochemically coupled. Their pool sizes, assessed by their magnetization ratios, have been extensively studied and reflect bioenergetics status in vivo. However, most such studies have ignored chemical exchange and T relaxation effects. In this work, we aimed to extend the T1nom method to simultaneously quantify the reaction rate constants as well as phosphorus metabolite pool size ratios under partially relaxed conditions.