Purpose To provide transmit whole‐brain coverage at 9.4 T using an array with only eight elements and improve the specific absorption rate (SAR) performance, a novel dipole array was developed, constructed, and tested. Methods The array consists of eight optimized bent folded‐end dipole antennas circumscribing a head. Due to the asymmetrical shape of the dipoles (bending and folding) and the presence of an RF shield near the folded portion, the array simultaneously excites two modes: a circular polarized mode of the array itself, and the TE mode (“dielectric resonance”) of the human head. Mode mixing can be controlled by changing the length of the folded portion. Due to this mixing, the new dipole array improves longitudinal coverage as compared with unfolded dipoles. By optimizing the length of the folded portion, we can also minimize the peak local SAR (pSAR) value and decouple adjacent dipole elements. Results The new array improves the SEE (< B1+>/√pSAR) value by about 50%, as compared with the unfolded bent dipole array. It also provides better whole‐brain coverage compared with common single‐row eight‐element dipole arrays, or even to a more complex double‐row 16‐element surface loop array. Conclusion In general, we demonstrate that rather than compensating for the constructive interference effect using additional hardware, we can use the “dielectric resonance” to improve coverage, transmit field homogeneity, and SAR efficiency. Overall, this design approach not only improves the transmit performance in terms of the coverage and SAR, but substantially simplifies the common surface loop array design, making it more robust, and therefore safer.

Purpose To improve the transmit (Tx) and receive (Rx) performance of a human head array and provide whole‐brain coverage at 9.4T, a novel 32‐element array design was developed, constructed, and tested. Methods The array consists of 18 transceiver (TxRx) surface loops and 14 Rx‐only vertical loops all placed in a single layer. The new design combines benefits of both TxRx and transmit‐only–receive‐only (ToRo) designs. The general idea of the design is that the total number of array elements (both TxRx and Rx) should not exceed the number of required Rx elements. First, the necessary number of TxRx loops is placed around the object tightly to optimize the Tx performance. The rest of the elements are loops, which are used only for reception. We also compared the performance of the new array with that of a state‐of‐the‐art ToRo array consisting of 16 Tx‐only loops and 31 Rx‐only loops. Results The new array provides whole‐brain coverage, ~1.5 times greater Tx efficiency and 1.3 times higher SNR near the brain center as compared to the ToRo array, while the latter delivers higher (up to 1.5 times) peripheral SNR. Conclusion In general, the new approach of constructing a single‐layer array consisting of both TxRx‐ and Rx‐only elements simplifies the array construction by minimizing the total number of elements and makes the entire design more robust and, therefore, safe. Overall, our work provides a recipe for a Tx‐ and Rx‐efficient head array coil suitable for parallel transmission and reception as well as whole‐brain imaging at UHF.

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