Double-row 18-loop transceive 32-loop receive tight-fit array provides for whole-brain coverage, high transmit performance, and SNR improvement near the brain center at 9.4T

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, similar to 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.