In Vivo Imaging and Spectroscopy of Dynamic Metabolism Using Simultaneous $^{13}$ C and $^1$ H MR

Hyperpolarized (HP) ¹³C-labeled pyruvate studies with magnetic resonance (MR) have been used to observe the kinetics of metabolism in vivo. Kinetic modeling to measure metabolic rates in vivo is currently limited because of nonspecific hyperpolarized signals mixing between vascular, extravascular, and intracellular compartments. In this study, simultaneous acquisition of both ¹H and ¹³ C signals after contrast agent injection is used to resolve specific compartments to improve the accuracy of the modeling. We demonstrate a novel technique to provide contrast to the intracellular compartments by sequential injection of HP [1-¹³C] pyruvate followed by gadolinium-chelate to provide T₁-shortening to extra-cellular compartments. A kinetic model that distinguishes the intracellular space and includes the T₁-shortening effect of the gadolinium chelate can then be used to directly measure the intracellular ¹³C kinetics.