Three-layered Radio Frequency Coil Arrangement for Sodium MRI of the Human Brain at 9.4 Tesla

Purpose: A multinuclei imaging setup with the capability to acquire both sodium (Na-23) and proton (H-1) signals at 9.4 Tesla is presented. The main objective was to optimize coil performance at the Na-23 frequency while still having the ability to acquire satisfactory H-1 images. Methods: The setup consisted of a combination of three radio frequency (RF) coils arranged in three layers: the innermost layer was a 27-channel Na-23 receive helmet which was surrounded by a four-channel Na-23 transceiver array. The outer layer consisted of a four-channel H-1 dipole array for B-0 shimming and anatomical localization. Transmit and receive performance of the Na-23 arrays was compared to a single-tuned Na-23 birdcage resonator. Results: While the transmit efficiency of the Na-23 transceiver array was comparable to the birdcage, the Na-23 receive array provided substantial signal-to-noise ratio (SNR) gain near the surface and comparable SNR in the center. The utility of this customized setup was demonstrated by Na-23 images of excellent quality. Conclusion: High SNR, efficient transmit excitation and B-0 shimming capability can be achieved for Na-23 MRI at 9.4T using novel coil combination. This RF configuration is easily adaptable to other multinuclei applications at ultra high field (>= 7T). (C) 2015 Wiley Periodicals, Inc.