Simultaneous whole-brain and cervical spine imaging at 7 T using a neurovascular head and neck coil with 8-channel transceiver array and 56-channel receiver array

Abstract

Purpose

To develop a 7T neurovascular head and neck (NVHN) coil with an extended longitudinal coverage of the brain and cervical spine, with eight transceiver (TxRx) channels and 56 receive (Rx) channels for dynamic parallel-transmit (pTx) applications.

Methods

A dual-row transceiver array with six elements in the upper row and two elements in the lower row was designed using combined electromagnetic and circuit optimization and constructed. A 56Rx array covering the brain and cervical spine was designed and combined with the transceiver array. The performance of the 8TxRx56Rx NVHN coil such as $B_1^{+}$, signal-to-noise ratio, and g-factor were validated in phantom and in vivo studies and compared with an in-house 8Tx64Rx head coil. High-resolution in vivo images were acquired with the NVHN and head coil.

Results

The average $B_1^{+}$ in phantom while exciting the upper six channels and all eight channels are 43.45 nT/V and 45.80 nT/V, respectively, demonstrating that the available $B_1^{+}$ field is seamlessly distributed in the brain and/or cervical spine, depending on the chosen excitation. The 8TxRx56Rx NVHN coil increases the SNR in the cervical spine and central brain by a factor of 2.18 and 1.16, respectively, compared with the 8Tx64Rx head coil. Furthermore, it demonstrates similar 1/g-factor performance for acceleration factors up to 5 × 5 compared with the head coil and provides diagnostic-quality images of the brain and spinal cord in a single acquisition.

Conclusion

The extended longitudinal coverage of the NVHN coil promises to improve the clinical application of the current generation of pTx 7T MRI systems with 8Tx channels.