  Multi-nuclear radio-frequency (RF) coils at ultrahigh field strengths are
challenging to develop due to the high operating frequency, increased
electromagnetic interaction among the coil elements, and increased
electromagnetic interaction between the coils and the subject. In this work, a
triple-nuclear surface coil for 1H, 13C, and 31P for small animal metabolic
imaging at 14.1 T is built by nesting three surface coil geometries: a
lumped-element L-C loop coil, a butterfly coil, and a microstrip transmission
line (MTL) resonator. The loop coil, butterfly coil, and MTL are tuned to 31P,
13C, and 1H, respectively. The successful bench tests and phantom imaging with
this novel triple-nuclear coil demonstrates the feasibility of the design for
triple-nuclear MR imaging and spectroscopy studies at the ultrahigh field of
14.1 T. In particular, the microstrip transmission line resonator demonstrates
excellent coil performance for proton imaging at 600 MHz, where conventional
lumped-element design is limited.
