Handheld electromagnet carrier for transfer of hyperpolarized carbon-13 samples

Purpose Hyperpolarization of carbon-13 (¹³C) nuclei by dissolution dynamic nuclear polarization increases signal-to-noise ratio (SNR) by >10,000-fold for metabolic imaging, but care must be taken when transferring hyperpolarized (HP) samples from polarizer to MR scanner. Some ¹³C substrates relax rapidly in low ambient magnetic fields. A handheld electromagnet carrier was designed and constructed to preserve polarization by maintaining a sufficient field during sample transfer. Methods The device was constructed with a solenoidal electromagnet, powered by a nonmagnetic battery, holding the HP sample during transfer. A specially designed switch automated deactivation of the field once transfer was complete. Phantom and rat experiments were performed to compare MR signal enhancement with or without the device for HP [¹³C]urea and [1-¹³C]pyruvate. Results The magnetic field generated by this device was tested to be >50 G over a 6-cm central section. In phantom and rat experiments, [¹³C]urea transported via the device showed SNR improvement by a factor of 1.8-1.9 over samples transferred through the background field. Conclusion A device was designed and built to provide a suitably high yet safe magnetic field to preserve hyperpolarization during sample transfer. Comparative testing demonstrated SNR improvements of approximately two-fold for [¹³C]urea while maintaining SNR for [1-¹³C]pyruvate.