Low‐cost LED‐based Photo‐CIDNP Enables Biocompatible Hyperpolarization of (19)F for NMR and MRI at 7 T and 4.7 T

Substrates containing (19)F can serve as background‐free reporter molecules for NMR and MRI. However, in vivo applications are still limited due to the lower signal‐to‐noise ratio (SNR) when compared with (1)H NMR. Although hyperpolarization can increase the SNR, to date, only photo‐chemically induced dynamic nuclear polarization (photo‐CIDNP) allows for hyperpolarization without harmful metal catalysts. Photo‐CIDNP was shown to significantly enhance (19)F NMR signals of 3‐fluoro‐DL‐tyrosine in aqueous solution using flavins as photosensitizers. However, lasers were used for photoexcitation, which is expensive and requires appropriate protection procedures in a medical or lab environment. Herein, we report (19)F MR hyperpolarization at 4.7 T and 7 T with a biocompatible system using a low‐cost and easy‐to‐handle LED‐based set‐up. First hyperpolarized (19)F MR images could be acquired, because photo‐CIDNP enabled repetitive hyperpolarization without adding new substrates.