  The design of a loop-gap-resonator RF coil optimized for ex vivo mouse brain
microscopy at ultra high fields is described and its properties characterized
using simulations, phantoms and experimental scans of mouse brains fixed in 10%
formalin containing 4 mM Magnevist. The RF (B1) and magnetic field (B0)
homogeneities are experimentally quantified and compared to electromagnetic
simulations of the coil. The coil's performance is also compared to a similarly
sized surface coil and found to yield double the sensitivity. A
three-dimensional gradient-echo (GRE) sequence is used to acquire high
resolution mouse brain scans at 47 {\mu}m3 resolution in 1.8 hours and a
20x20x19 {\mu}m3 resolution in 27 hours. The high resolution obtained permitted
clear visualization and identification of multiple structures in the ex vivo
mouse brain and represents, to our knowledge, the highest resolution ever
achieved for a whole mouse brain. Importantly, the coil design is simple and
easy to construct.
