Magnetic resonance in medicine · 2025
A shielded 32-channel body transceiver array with integrated electronics for 7 T.
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Haluptzok Tobey D, Lagore Russell L, Schmidt Simon, Metzger Gregory J
Аннотация
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 B 1 + $$ {\mathrm{B}}_1^{+} $$ 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 B 1 + $$ {B}_1^{+} $$ /W0.5 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.
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 B 1 + $$ {\mathrm{B}}_1^{+} $$ 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 B 1 + $$ {B}_1^{+} $$ /W0.5 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.