Autonomous cryogenic RF receive coil for 13C imaging of rodents at 3 T

Purpose To develop an autonomous, in‐bore, MR‐compatible cryostat cooled with liquid nitrogen that provides full‐day operation, and to demonstrate that the theoretical signal‐to‐noise benefit can be achieved for 13C imaging at 3 T (32.13 MHz). Methods The cryogenic setup uses a vacuum‐insulated fiberglass cryostat, which indirectly cools a cold finger where the RF coil is attached. The cryostat was evacuated before use and had a reservoir of liquid nitrogen for full‐day operation. A 30 × 40 mm2 copper coil was mounted inside the cryostat with a 3‐mm distance to the sample. Two examples of in vivo experiments of rat brain metabolism after a hyperpolarized [1‐13C]pyruvate injection are reported. Results A coil Q‐factor ratio of Q88K/Q290K = 550/280 was obtained, and the theoretical SNR enhancement was verified with MR measurements. We achieved a coil temperature of 88 K and a preamplifier temperature of 77 K. A 2‐fold overall SNR enhancement was achieved, compared with the best case at room temperature. The thermal performance of the coil was adequate for in vivo experiments, with an autonomy of 5 hours consuming 6 L of LN2, extendable to over 12 hours by LN2 refilling. Conclusion Cryogenic surface coils can be highly beneficial for 13C imaging, provided that the coil‐to‐sample distance remains short. An autonomous, in‐bore cryostat was developed that achieved the theoretical improvement in SNR.