Abstract. Magnetic resonance imaging and spectroscopy often suffer from a
low intrinsic sensitivity, which can in some cases be circumvented by the
use of hyperpolarization techniques. Dissolution-dynamic nuclear
polarization offers a way of hyperpolarizing 13C spins in small
molecules, enhancing their sensitivity by up to 4 orders of magnitude.
This is usually performed by direct 13C polarization, which is
straightforward but often takes more than an hour. Alternatively, indirect
1H polarization followed by 1H→13C polarization transfer
can be implemented, which is more efficient and faster but is technically
very challenging and hardly implemented in practice. Here we propose to
remove the main roadblocks of the 1H→13C polarization
transfer process by using alternative schemes with the following: (i) less rf (radiofrequency) power; (ii) less
overall rf energy; (iii) simple rf-pulse shapes; and (iv) no synchronized 1H and
13C rf irradiation. An experimental demonstration of such a simple
1H→13C polarization transfer technique is presented for the
case of [1-13C]sodium acetate, and is compared with the most
sophisticated cross-polarization schemes. A polarization transfer efficiency
of ∼0.43 with respect to cross-polarization was realized,
which resulted in a 13C polarization of ∼8.7 % after
∼10 min of microwave irradiation and a single
polarization transfer step.
Simple and Cost-Effective Cross-Polarization Experiments under Dissolution-Dynamic Nuclear Polarization Conditions with a 3D-Printed 1H-13C Background-Free Radiofrequency Coil
