  Purpose: A novel dissolution dynamic nuclear polarization (dDNP) polarizer
platform is presented. The polarizer meets a number of key requirements for in
vitro, pre-clinical and clinical applications. Method: It uses no liquid
cryogens, operates in continuous mode, accommodates a wide range of sample
sizes up to and including those required for human studies, and is fully
automated. Results: It offers a wide operational window both in terms of
magnetic field, up to 10.1 T, and temperature, from room temperature down to
1.3 K. The polarizer delivers a 13C liquid state polarization for
[1-13C]pyruvate of 70%. The build-up time constant in the solid state is
approx. 1200 s (20 min), allowing a sample throughput of at least one sample
per hour including sample loading and dissolution. Conclusion: We confirm the
previously reported strong field dependence in the range 3.35 to 6.7 T, but see
no further increase in polarization when increasing the magnetic field strength
to 10.1 T for [1-13C]pyruvate and trityl. Using a custom dry magnet, cold head
and recondensing, closed-cycle cooling system, combined with a modular DNP
probe, automation and fluid handling systems; we have designed a unique dDNP
system with unrivalled flexibility and performance.
