A multisample dissolution dynamic nuclear polarization system for serial injections in small animals

Purpose Several in vivo applications of dissolution dynamic nuclear polarization (DNP) require rapid successive injections of hyperpolarized substrates. Here we present the design and performance of a custom‐built multisample dissolution DNP setup for small animal research. Methods The DNP setup consists of a commercial wide‐bore magnet charged to 3.35 T, a cryostat, a 94‐GHz microwave source, and a custom‐built skeleton that accommodates four identical sample sticks. Each sample stick features a dissolver locked into the skeleton port and a lifter, which permits moving the sample cup out of the liquid helium bath for dissolution. Results The dissolution of the first sample was triggered after 2 hours of polarization buildup during single‐shot operation of the cryostat. Thereafter, a time window of 75–90 min was available to dissolve the remaining three polarized samples. The average liquid state polarization over all four sticks was measured as 18.7% ± 2.3% for [1‐13C] pyruvate 30 s after dissolution. In vivo applicability of the setup using serial injections of [1‐13C] pyruvate to study cardiac metabolism in rats revealed good reproducibility. Conclusion The proposed four‐sample DNP insert provides reproducible liquid state polarization of [1‐13C] pyruvate and allows for rapid repeat injections in small animals. Magn Reson Med 77:904–910, 2017. © 2016 International Society for Magnetic Resonance in Medicine