RF-coil with variable resonant frequency for multiheteronuclear ultra-high field MRI

•A coil for broad range heteronuclear ultra-high field imaging is proposed•The coil properties are studied numerically and experimentally•The non-proton coil is tuned by changing its structural capacitance and inductance•1H and X-nuclei coils are uncoupled so they can be tuned independently•The magnetic field distribution show the coils to allow scanning small animals Here we propose double-coil setup to allow high signal-to-noise ratio broad-range heteronuclear magnetic resonance imaging experiments: two independent coils, one of them tuned to 1H frequency to perform anatomical 1H imaging, and another one, metamaterial-inspired coil, tuned to the X-nucleus frequency. In this work our goal was to design a broad-range X-nuclei coil to cover 2H, 11B, 13C, 23Na, 7Li and 31P nuclear magnetic resonance frequencies, and to combine it with 1H coil in one setup. The system was designed for 11.7 T scanner, i.e., with 76–203 MHz frequency tuning range for the X-nuclei and tuned to 500 MHz for the proton coil. X-nuclei coil operates via excitation of the fundamental eigenmode of an array of parallel non-magnetic wires. The excitation of the array is provided via non-resonant feeding loop inductively coupled to the resonator. In order to tune the X-coil over such a wide range, both structural capacitance and inductance of the coil were made variable; narrow range tuning of the 1H coil is achieved via conventional tuning-matching circuit. Here, the design principle and setup tunability were investigated in simulations and experimentally.