A shielded 32‐channel body transceiver array with integrated electronics for 7 T

Abstract Purpose Develop a 32‐channel transceiver array for 7 T body imaging that incorporates an RF shield, improves SNR, lowers g‐factors, and is robust to external loading. Methods The addition of a local RF shield was first investigated for single resonant blocks consisting of either one loop and a dipole (LD) or three loops and a dipole (3LD). A 32‐channel array consisting of eight shielded 3LD blocks (32LD‐SH) was constructed and validated for in‐vivo use. The SNR, parallel imaging, and transmit performance were compared to a previously published 16‐channel LD array (16LD). The effect of top loading was investigated by placing arms on top of the coils and measuring S‐parameter changes. In vivo imaging of multiple anatomies was performed. Results In single block experiments, the RF shield impacted SNR and performance by <5%. The 3LD blocks had 80% higher peripheral SNR and 25% higher SNR at a depth of 10 cm. The 32LD‐SH array had 18% lower /W 0.5 efficiency and 30% higher central SNR compared to the 16LD array and supported threefold acceleration in the foot–head direction. Arm placement had no effect on the 32LD‐SH array but reduced the 16LD match to 5.4 dB. Conclusion A 32‐channel transceiver array was developed for 7 T body imaging that is insensitive to top loading and has higher SNR and lower g‐factors compared to an existing 16‐channel transceiver array. Despite lower transmit performance, parallel transmit optimization permitted the 32LD‐SH to achieve flip angles necessary for high‐quality gradient and spin echo acquisitions of target organs in the chest, abdomen, and pelvis.