In vivo MRI of knee using a metasurface-inspired wireless coil

Purpose: To investigate the application of a metasurface-inspired wireless coil and evaluate its performance in clinical knee MRI.Methods: A metasurface surface coil is designed for knee MRI at 1.5T. The image SNR and uniformity are assessed using a water phantom. In vivo studies are performed on 10 healthy volunteers (age range, 24-30 y; three males) and two patients (ages 31 and 76 y; two males) with knee conditions. A commercial 4-channel flexible coil and a 12-channel knee coil are used for comparison. The SNRs of different tissues on knee MRI images are evaluated and compared. The image quality is evaluated using a five-point Likert scale.Results: The SNRs of the images acquired by the metasurface coil with spine coil as receiving coil are similar to the 12-channel knee coil, whereas the uniformity from groups where the metasurface coil was used is higher than that acquired by conventional coils in phantom studies. For in vivo knee MRI, the SNRs of the images acquired by the metasurface coil with spine coil as receiving coil are between that of the 4- and 12-channel phased-array coils. The image quality scores evaluated by radiologists are higher when metasurface is used.Conclusion: The metasurface-inspired wireless coil is applicable to clinical knee MRI. When used in conjunction with the spine coil, it provides a favorable SNR between that of the 4- and 12-channel phased-array coil at 1.5T MRI system. The metasurface coil improves image uniformity regardless of which coil is used as the receiving coil.