Thermal annihilation of photo-induced radicals following dynamic nuclear polarization to produce transportable frozen hyperpolarized C-substrates.

Hyperpolarization via dynamic nuclear polarization (DNP) is pivotal for boosting magnetic resonance imaging (MRI) sensitivity and dissolution DNP can be used to perform in vivo real-time C MRI. The type of applications is however limited by the relatively fast decay time of the hyperpolarized spin state together with the constraint of having to polarize the C spins in a dedicated apparatus nearby but separated from the MRI magnet. We herein demonstrate that by polarizing C with photo-induced radicals, which can be subsequently annihilated using a thermalization process that maintains the sample temperature below its melting point, hyperpolarized C-substrates can be extracted from the DNP apparatus in the solid form, while maintaining the enhanced C polarization. The melting procedure necessary to transform the frozen solid into an injectable solution containing the hyperpolarized C-substrates can therefore be performed ex situ, up to several hours after extraction and storage of the polarized solid.