Dissolution Dynamic Nuclear Polarisation (dDNP) is an experimental technique
that increases the sensitivity of magnetic resonance experiments by more than a
factor of $10^5$, permitting isotopically-labelled molecules to be transiently
visible in MRI scans with their biochemical fates spatially resolvable over
time following injection into a patient. dDNP requires a source of unpaired
electrons to be in contact with the isotope-labelled nuclei, cooled to
temperatures close to absolute zero, and spin-pumped into a given state by
microwave irradiation. At present, these electrons are typically provided by
chemical radicals which require removal by filtration prior to injection into
humans. Alternative sources include UV irradiation, requiring storing samples
in liquid nitrogen, or cobalt-60 gamma irradiation, which requires days and
generates polarisation two to three orders of magnitude lower than chemical
radicals. In this study, we present ultra-high dose rate electron beam
irradiation as a novel alternative for generating non-persistent radicals in
glycerol/alanine mixtures. These radicals are stable for months at room
temperature, are present at concentrations dependent on irradiation dose, Und
generate comparable nuclear polarisation to the typically used trityl radicals
(20%) through a novel mechanism. The process of their generation inherently
sterilises samples, and they enable the imaging of alanine metabolism in vivo
using dDNP. This new method of generating radicals for dDNP offers the
potential to report on relevant biological processes while being translatable
to the clinic.

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