9.4T double‐tuned 13C/1H human head array using a combination of surface loops and dipole antennas

• Published in: NMR in biomedicine Vol. 34; no. 10
• Main Authors: Avdievich, Nikolai I, Solomakha, Georgiy, Ruhm, Loreen, Henning, Anke, Scheffler, Klaus
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01-10-2021
• Subjects: Biological products; Dipole antennas; Magnetic resonance imaging; Magnetic resonance spectroscopy; Medical imaging; Neuroimaging
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.4577

MRI at ultra‐high field (UHF, ≥7 T) provides a natural strategy for improving the quality of X‐nucleus magnetic resonance spectroscopy and imaging due to the intrinsic benefit of increased signal‐to‐noise ratio. Considering that RF coils require both local transmission and reception at UHF, the designs of double‐tuned coils, which often consist of several layers of transmit and receive resonant elements, become quite complex. A few years ago, a new type of RF coil, ie a dipole antenna, was developed and used for human body and head imaging at UHF. Due to the mechanical and electrical simplicity of dipole antennas, combining an X‐nucleus surface loop array with 1H dipoles can substantially simplify the design of a double‐tuned UHF human head array coil. Recently, we developed a novel bent folded‐end dipole transceiver array for human head imaging at 9.4 T. The new eight‐element dipole array demonstrated full brain coverage, and transmit efficiency comparable to that of the substantially more complex 16‐element surface loop array. In this work, we developed, constructed and evaluated a double‐tuned 13C/1H human head 9.4 T array consisting of eight 13C transceiver surface loops and eight 1H transceiver bent folded‐end dipole antennas all placed in a single layer. We showed that interaction between loops and dipoles can be minimized by placing four 1H traps into each 13C loop. The presented double‐tuned RF array coil substantially simplifies the design as compared with the common double‐tuned surface loop arrays. At the same time, the coil demonstrated an improved 1H longitudinal coverage and good transmit efficiency.