A broad tuneable birdcage coil for mouse ¹H/¹⁹F MR applications

In this paper, we present the design and implementation of a ¹H/¹⁹F volume coil for mouse body magnetic resonance (MR) imaging and spectroscopy using a high magnetic field (4.7 T). By changing the geometry of the coil rungs to include both nuclei for MR experiments, this innovative coil can be tuned over an extremely wide range of frequency. The coil, 45 mm in diameter and 55 mm in length, consists of a 12-rung birdcage-like structure. Using two types of tuning, the coil can generate a sufficiently homogeneous B₁⁺ electromagnetic field within a working volume optimized for laboratory mouse. The first tuning involves changing the resonance frequency over a large frequency range. The electrical capacitance between the wires can be adjusted to reflect changes in the length of the coil. The second tuning comprises a habitual tuning transformer for precise detection in a narrow band. In contrast to widely used multinuclear coils, the coil presented here features only one resonance peak and can be manipulated according to the Larmor frequencies given for ¹H and ¹⁹F. The coil was successfully tested using full-wave simulations of magnetic and electric field distributions under in vivo MR conditions.