High‐performance radiofrequency coils for 23Na MRI: brain and musculoskeletal applications

23Na RF coil design for brain and MSK applications presents a number of challenges, including poor coil loading for arrays of small coils and SNR penalties associated with providing 1H capability with the same coil. The basics of RF coil design are described, as well as a review of historical approaches to dual tuning. There follows a review of published high performance coil designs for MSK and brain imaging. Several coil designs have been demonstrated at 7T and 3T which incorporate close‐fitting receive arrays and in some cases design features which provide 1H imaging with little penalty to 23Na sensitivity. The “nested coplanar loop” approach is examined, in which small transmit‐receive 1H elements are placed within each 23Na loop, presenting only a small perturbation to 23Na performance and minimizing RF shielding issues. Other designs incorporating transmit‐receive arrays for 23Na and 1H are discussed including a 9.4 T 23Na / 1H brain coil. Great gains in 23Na SNR have been made with many of these designs, but simultaneously achieving high performance for 1H remains elusive. Copyright © 2015 John Wiley & Sons, Ltd.