Gradient Metamaterial for Clinical Supine Wrist Magnetic Resonance Imaging

Abstract

Wrist magnetic resonance imaging (MRI) is essential for evaluating soft‐tissue injury, bone marrow edema, and small‐joint abnormalities, yet high‐quality imaging still relies largely on dedicated wrist coils and often requires the uncomfortable prone “superman” position. Here, we present a clinically adaptive gradient metamaterial for supine wrist MRI. The conformal structure is built from split elliptical‐ring resonators and integrates a parallel inductor‐capacitor trap‐mediated nonlinear response with gradient‐capacitance shimming, enabling transmit‐phase detuning, receive‐phase resonance, and axial field homogenization within a compact architecture. On a 1.5 T clinical MRI system, simulations, phantom experiments, and in vivo studies in 23 participants (including one special case) are demonstrated. When integrated with a flex coil, the metamaterial‐assisted configuration achieved about 1.5 times in vivo signal‐to‐noise ratio and contrast‐to‐noise ratio gains compared with a dedicated 12‐channel wrist coil. When operated with a body coil, the same metamaterial provided a portable, low‐complexity imaging configuration with comparable or superior image quality in several clinical assessments. Both configurations improved patient comfort and showed diagnostic agreement with standard wrist‐coil imaging. This work establishes a materials‐design‐driven strategy for translating metamaterials into patient‐centered clinical MRI.