Design of a local transmit RF-resonator with enhanced local B1+-field for improved abdominal imaging in a single-sided low-field system

Motivation: Low-field, single-sided MR systems could be used for image-guided abdominal therapies. However, deeper tissue imaging requires Tx coils with stronger B1+-fields. Goal(s): We have designed a transmit RF-resonator that enhances B1+-field at depth, facilitating imaging over an extended FOV. Approach: Pulse sequences were modified with short refocusing pulses and long echo trains to leverage the stronger B1-field. Phantom studies compared the imaging performance of the RF-resonator with the Promaxo system's Tx coil. Results: The results indicate that the local transmit RF-resonator provides a 30% increase in overall B1+-field, yielding a 4-fold enhancement of image SNR, thereby enabling deeper low-field abdominal imaging. Impact: Low-field, open MR systems allow for image-guided abdominal therapies but are limited by B1+-field strength and penetration depth. The proposed local Tx RF-resonator enhances transmit efficiency and image quality, enabling deeper, more effective low-field abdominal imaging.