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Abstract:
X-nuclei (13C,31P etc.) MRI and MRS provide valu- able information for biomedical research and can benefit from the SNR increase at ultra-high field (UHF, 7T and above). UHF, however, brings the necessity of local transmission (Tx) and reception (Rx) capabilities within the structure of the same double-tuned (DT) RF coil. Hence, in the case of the double-layer Tx-only/Rx-only (ToRo) design [1], the DT coil must include four layers (2 Tx and 2 Rx) interacting with each other. In practice, such a complicated design has rarely been used. Use of transceiver (TxRx) arrays greatly simplifies the DT array by decreasing the number of layers to two [2–5]. Still, to minimize interaction, often 1H-layer is moved away from the sample [2,3]. This decreases the 1H SNR [2]. Having good performance at both X and 1H frequencies is very important. Recently, we demon- strated that by placing both the 1H and 31P loop arrays into the same tight-fitting layer preserves the 1H Tx-efficiency and central SNR [5]. However, we had to reduce the total number of loops to 20. Further improvement in SNR requires more Rx elements, which is very dif- ficult to realize using common loops due to the design complexity. At UHF, the array design can be greatly simplified by using 1H dipoles [6]. Combining 8 TxRx loops (X-nuclei) with 8 TxRx dipoles (1H) for human head imaging has been reported at 9.4T [7] and 7T [8]. In this work, we developed a novel UHF densely-populated tight- fitting loop/dipole DT array in which we increased the number of TxRx elements, all placed in one layer, to 32.
