An 8‐dipole transceive and 24‐loop receive array for non‐human primate head imaging at 10.5 T

A 32‐channel RF coil was developed for brain imaging of anesthetized non‐human primates (rhesus macaque) at 10.5 T. The coil is composed of an 8‐channel dipole transmit/receive array, close‐fitting 16‐channel loop receive array headcap, and 8‐channel loop receive array lower insert. The transceiver dipole array is composed of eight end‐loaded dipole elements self‐resonant at the 10.5 T proton Larmor frequency. These dipole elements were arranged on a plastic cylindrical former, which was split into two to allow for convenient animal positioning. Nested into the bottom of the dipole array former is located an 8‐channel loop receive array, which contains 5 × 10 cm2 square loops arranged in two rows of four loops. Arranged in a close‐fitting plastic headcap is located a high‐density 16‐channel loop receive array. This array is composed of 14 round loops 37 mm in diameter and 2 partially detachable, irregularly shaped loops that encircle the ears. Imaging experiments were performed on anesthetized non‐human primates on a 10.5 T MRI system equipped with body gradients with a 60 cm open bore. The coil enabled submillimeter (0.58 mm isotropic) high‐resolution anatomical and functional imaging as well as tractography of fasciculated axonal bundles. The combination of a close‐fitting loop receive array and dipole transceiver array allowed for a higher‐channel‐count receiver and consequent higher signal‐to‐noise ratio and parallel imaging gains. Parallel imaging performance supports high‐resolution functional MRI and diffusion MRI with a factor of three reduction in sampling. The transceive array elements during reception contributed approximately one‐quarter of the signal‐to‐noise ratio in the lower half of the brain, which was farthest from the close‐fitting headcap receive array. Described is a 32‐channel receive array for high‐resolution brain imaging of rhesus macaques at 10.5 T. The coil is composed of an 8‐channel transmit/receive dipole array, a close‐fitting 16‐channel loop receive array headcap, and an 8‐channel loop receive array located under the chin. This coil system is capable of anatomical and diffusion imaging at down to 0.5 mm isotropic resolution with a threefold reduction in sampling time.