Enhancing SNR in MRI at 7T using wearable coils, dielectric resonators, and dipole antennas

The twisted-pair (TP) coil design is a promising strategy for developing novel, flexible, wearable MRI detectors that can provide SNR gains in various clinical applications of high-field MRI. We hypothesize that the TP coil's receive (Rx) sensitivity can be significantly increased by combining it with two complementary elements, such as dielectric resonators (DRs) and dipole antennas.

TP coils were combined with DRs made of high-permittivity material (ε_r = 1070) and transceiver (TxRx) dipole antennas. The Tx and Rx performance of six different types of arrays (TP-only, dipole-only, TP with DRs, dipole with DRs, dipole with TPs, and dipole with TPs and DRs) was investigated through numerical simulations involving a cylindrical phantom suitable for lower extremity applications and two human voxel models. MR phantom experiments were conducted using a 7 Tesla whole-body MRI scanner to validate the Tx and Rx performance of all six array types.

The array combining all three types of elements (TP coils, DRs, and dipole antennas) provided the highest overall Rx performance; MR phantom experiments showed that integrating DRs with TP coils increased peripheral SNR by 250% and central SNR by 23% (for a total 38% gain in the center when also using dipole antennas in Rx). Human voxel model simulations confirmed that similar SNR gains can be achieved in vivo. Integrating DRs into TP coils also increased central Tx field efficiency by 4.6% and reduced the peak SAR_10g by 25.8% in the human voxel model Hugo.

DRs and dipole antennas can significantly improve the overall Rx performance of TP coils. This concept can benefit MRI of the human lower extremity at 7 Tesla and encourage exploration of its utility for other clinical applications.