研究目的

To propose a compact, lightweight, and easy-to-fabricate Hilbert curve-based metasurface resonator that can effectively increase the sensitivity and penetration depth of an RF coil for 7-T magnetic resonance imaging scanner.

研究成果

A subwavelength metasurface resonator based on a Hilbert curve is presented for field enhancement deep into the imaging volume for an RF coil for 7-T MRI. A unit cell of a TEM coil was used in the study. The coil and a fourth-order Hilbert curve-based unit cell were fabricated for experiments. The effectiveness of RF field enhancement was successfully demonstrated using both simulation and experimental data. A magnetic field enhancement of more than four times at the depth of 13.5 cm into the imaging volume is observed experimentally. A circuit model is proposed for a fast estimation of the resonance of Hilbert curve of a given order with significantly improved accuracy.

研究不足

The physical size of metamaterials is the major limitation when they are applied to an RF system in an MRI scanner. The operating frequency of an intermediate (1–3 T) to ultrahigh-field (UHF >7 T) MRI scanner is in the range of approximately 40–400 MHz. Therefore, the size of a unit cell for metamaterials is in the centimeter to tens of centimeters range, which can often be impractical for the limited space available inside a scanner.