Co-polarization of (1-13C) Pyruvate and 13C Sodium Bicarbonate by Dynamic Nuclear Polarization allows Simultaneous Assessment of in vivo pH and Tumor Metabolism

INTRODUCTION: The molecular probes used in hyperpolarized C spectroscopy have important advantages over contrast agents currently in clinical use, expected to have little or no toxicity in humans, even at relatively high concentrations. This feature is particularly appealing given recent concerns about contrast nephropathy associated with iodinated CT contrast, as well as nephrogenic systemic fibrosis (NSF) seen in patients receiving gadolinium chelates for MR[1,2]. Many new C agents may be appropriate for metabolic imaging in humans. In addition to C pyruvate, C lactate itself is a promising primary agent for cancer imaging[3]. Other recent work has demonstrated in vivo pH mapping using C bicarbonate, by hyperpolarization of C cesium bicarbonate followed by an ion exchange method to exchange most of the Cs for sodium[4]. In this abstract, a method for direct polarization of C sodium bicarbonate is reported, that is suitable for use in humans. This method has been combined with a copolarization approach that allows simultaneous polarization of C bicarbonate and C pyruvate, to perform both pH and metabolic mapping in vivo using a single contrast bolus.