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

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 C imaging at 3 T (32.13 MHz). 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 mm 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- C]pyruvate injection are reported. A coil Q-factor ratio of Q /Q = 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 LN , extendable to over 12 hours by LN refilling. Cryogenic surface coils can be highly beneficial for C imaging, provided that the coil-to-sample distance remains short. An autonomous, in-bore cryostat was developed that achieved the theoretical improvement in SNR.