Circularly polarized metamaterial cage for homogeneous signal-to-noise ratio enhancement in magnetic resonance imaging

TL;DR

This paper introduces a wireless metamaterial cage that enhances MRI signal-to-noise ratio uniformly across the imaging region, using a novel circularly polarized design to improve image quality without sacrificing homogeneity.

Contribution

A novel cylindrical metamaterial cage with circular polarization is engineered for homogeneous SNR enhancement in MRI at 3.0 T, outperforming existing coils in SNR and uniformity.

Findings

32-fold SNR enhancement with maintained homogeneity

At least 1.94-fold higher SNR than extremity coil in axial plane

Significantly lower SNR variation (12.07%) compared to traditional coils

Abstract

The signal-to-noise ratio (SNR) in magnetic resonance imaging (MRI) governs the quality of signal detection and directly impacts the clarity and reliability of the acquired images. Recent advances in metamaterials have enabled lightweight solutions with selective magnetic responses, offering a route to locally boost SNR in targeted anatomical regions but often with compromised field homogeneity. Here, a wireless metamaterial cage constructed from coaxial cables is engineered for homogeneous SNR enhancement at 3.0 T. With its cylindrical geometry and electromagnetic architecture, the device supports circularly polarized resonance through engineered phase-shifted currents, enabling selective and omnidirectional interaction with the rotating B_1^- field to achieve uniform magnetic field distribution. Integrated with the body coil, the device yields a 32-fold SNR enhancement while maintaining comparable homogeneity to the body coil alone, exhibiting only 12.07% variation within the region of interest (ROI). Benchmarking against a state-of-the-art 16-channel extremity coil further shows that the metacage achieves at least 1.94-fold and 2.24-fold higher SNR in axial and coronal planes, respectively, and exhibits substantially lower SNR variation (12.07% compared to 54.83% for the extremity coil). The results establish the metacage as a compelling platform for next-generation wireless MRI technologies.