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 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 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 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 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 F MR images could be acquired, because photo-CIDNP enabled repetitive hyperpolarization without adding new substrates.