NMR Hyperpolarization of Established PET Tracers

The development of sensitive probes for directly measuring in vivo processes is at the forefront of medical imaging. In the case of magnetic resonance imaging (MRI) the detection of a small number of molecules is a major challenge due to its limited sensitivity. This problem can be tackled by hyperpolarization, which increases the NMR signals up to several orders of magnitude. In this contribution NMR hyperpolarization of non-radioactive counterparts of two well-established positron emission tomography (PET) tracers, namely O-(2-[F-18] fluoroethyl)-L-tyrosine ([F-18]FET) and [F-18]fallypride ([F-18]FP), via para-hydrogen induced polarization (PHIP), to investigate oncological and neurological questions is demonstrated. Significant H-1/(CNMR)-C-13 signal enhancements of several thousand were achieved for both tracers. Partial deuteration of the C-13-labeled [F-18]FET analog resulted in T-I times up to similar to 36 s. Hence, this molecule is a candidate for an MRI contrast agent, allowing follow-up MRI examinations with close succession in time.