Methods of hyperpolarization based on parahydrogen have been expanding recently from the early applications in hydrogenation chemistry to biomedical imaging where they are expected to yield similar information as the competing technology, dynamic nuclear polarization, (DNP). These hyperpolarization experiments have already enabled the measurement of metabolism in vivo at temporal resolutions of seconds. When infused into organisms harboring tumor cells, molecules such as pyruvate and lactate have been shown to be sufficiently long-lived to infiltrate cellular metabolic cycles and be converted at different rates in cancer versus normal tissue. DNP has been used most frequently in these early studies, owing to commercial availability and the flexibility to polarize small molecules such as pyruvate and lactate. Techniques based on chemical addition or exchange of parahydrogen have also shown promise for generating metabolic contrast in vivo at similar levels of signal enhancement and at lower costs.
