A Near-Field Coupling Array Enables Parallel Imaging and SNR Gain in MRI

Wireless radiofrequency (RF) coils based on metasurfaces hold great promise for improving clinical magnetic resonance imaging (MRI) workflows by eliminating the need for cable connections to the patient bed and simplifying coil structures. A fundamental requirement for their clinical adoption is the ability to support parallel imaging, which reduces examination time and improves efficiency. Moreover, the implementation of parallel imaging often comes at the expense of image signal-to-noise ratio (SNR). Although several wireless RF coils incorporating metamaterials are reported, most do not support parallel imaging and many deliver suboptimal SNR performance. In this work, a novel wireless RF coil architecture is proposed, termed the near-field coupling array (NFCA), which demonstrates both excellent SNR performance and robust parallel imaging capabilities. A general theoretical framework is presented that establishes a foundation for applying metasurface arrays in magnetic resonance RF coil design. The SNR expression for this architecture is derived from two perspectives, and its fundamental principles are validated through case studies. Experimental results show that the NFCA achieves a 66% SNR improvement over a conventional commercial RF coil architecture (i.e., a wired coil) while its average acceleration factor exceeds 94% of that of the commercial coil.