A practical multinuclear transceiver volume coil for in vivo MRI/MRS at 7 T

A practical multinuclear transceiver RF volume coil with improved efficiency for in vivo small animal (1)H/(13)C/(23)Na MR applications at the ultrahigh magnetic field of 7 T is reported. In the proposed design, the coil's resonance frequencies for (1)H and (13)C are realized by using a traditional double-tuned approach, while the resonant frequency for (23)Na, which is only some 4 MHz away from the (13)C frequency, is tuned based upon (13)C channel by easy-operating capacitive "frequency switches". In contrast to the traditional triple-tuned volume coil, the volume coil with the proposed design possesses less number of resonances, which helps improve the coil efficiency and alleviate the design and operation difficulties. This coil design strategy is advantageous and well suitable for multinuclear MR imaging and spectroscopy studies, particularly in the case where Larmor frequencies of nuclei in question are not separate enough. The prototype multinuclear coil was demonstrated in the desired unshielded design for easy construction and experiment implementation at 7 T. The design method may provide a practical and robust solution to designing multinuclear RF volume coils for in vivo MR imaging and spectroscopy at ultrahigh fields. Finite difference time domain method simulations for evaluating the design and 7-T MR experiment results acquired using the prototype coil are presented.