Flexible Metasurface-Loaded RF Coil for 3T MRI Articular Cartilage Imaging

Traditional articular MRI using rigid coils presents challenges such as limited coverage, patient discomfort, signal loss, suboptimal coil positioning, and workflow inefficiencies, significantly impacting image quality and patient comfort, especially for complex joints. Developing flexible RF coils offers a solution by improving adaptability to anatomical structures, enhancing patient comfort, and increasing diagnostic precision. This paper proposes a flexible metasurface-loaded RF coil with impedance matching for 3 Tesla (128 MHz) articular imaging applications. The design integrates a spiral-structured RF coil metasurface, enabling superior image quality in a compact form. The initial singlechannel RF coil exhibits an improper input impedance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${Z}_{{in }}=50(0.009+j 9.381) \Omega$</tex> at 128 MHz. To achieve proper impedance matching, a capacitor-capacitor (CC) matching network is introduced, ensuring efficient power transfer. After matching, the RF coil achieves a return loss of -15 dB, indicating improved performance. Constructed from a lightweight and durable FR4 substrate with a thickness of 0.7 mm, the flexible RF coil promotes optimal positioning. By overcoming the limitations of traditional rigid coils, the proposed solution has the potential to advance MRI technology, better aligning with the evolving demands of medical diagnostics and enhancing both imaging quality and the patient experience.