Diagnostic Performance of a Metasurface Coil Compared With a Commercial 12-Channel Coil for Knee MRI at 1.5 T

Knee MRI image quality depends largely on the radiofrequency coil; metasurfaces offer a new approach to improving coil performance.

To evaluate the imaging performance and diagnostic capability of a metasurface coil for knee MRI.

Prospective.

A cylindrical phantom, 60 healthy volunteers (36 females; median age, 33), and 52 patients with knee injuries (28 females; median age, 47).

T1 Weighted Spin Echo (T1W SE), Fat-Saturated Proton Density-Weighted Fast Spin-Echo (FS PDW FSE), T1-Weighted Gradient Recalled Echo (T1W GRE) at 1.5 T.

All subjects underwent paired scanning with a wireless metasurface coil (plus built-in spine array) and a commercial 12-channel knee coil. Phantom metrics included signal-to-noise ratio (SNR), percent image uniformity (PIU), ghost-to-signal ratio, and B1 mapping. Volunteers were scored for image quality (5-point), SNR, contrast-to-noise ratio (CNR), and handling convenience. Patients were assessed for ACL, meniscal, and cartilage injuries against arthroscopy.

T-test and Wilcoxon signed-rank test for quantitative and semi-quantitative data; McNemar test for diagnostic efficacy. Kendall's coefficient of concordance and kappa, with p < 0.05 considered significant.

In the phantom, SNR was 196.14 versus 183.34, PIU 92.47% versus 71.30%, and ghost-to-signal ratio 0.0093 versus 0.0145 (metasurface vs. commercial coil). Measured flip angle was 44.7° ± 1.31° (0.67% deviation from nominal 45°); B1 field uniformity was 91.14%. In volunteers, subjective image quality scores were slightly higher for the 12-channel coil on FS PDW FSE (p < 0.05), whereas scores were comparable on T1W SE and 3D FS T1W GRE (p = 0.06, 0.38). Convenience was markedly better for the metasurface (5.0 vs. 4.0, p < 0.05). In patients, diagnostic sensitivity (72.7%-83.3% vs. 72.7%-81.5%), specificity (86.7%-96.4% vs. 85.6%-96.4%), and accuracy (82.1%-90.4% vs. 81.4%-88.5%) were comparable between coils, inter-coil kappa was 0.884-1.000. "DATA" CONCLUSION: The wireless metasurface coil was more convenient and provided image quality and diagnostic performance comparable to the 12-channel commercial knee coil at 1.5 T.

2.

Stage 3.