设计了一种可用于超高场磁共振成像(MRI)的负磁导率超材料磁感应透镜(MIL), 可以有效提高MRI的信噪比.MIL是由6×6个加载电容的金属开口谐振环组成的二维周期结构, 并将其加工在一层0.6 mm 厚度的FR-4介质基板上.将MIL放置于射频线圈和样品之间, 能够实现等效的磁表面等离激元效应.MIL单元电磁场分布、散射参数和等效磁导率的仿真结果表明：所设计的MIL在拉莫尔进动频率297.2 MHz产生负的磁导率, 并能增强由射频线圈产生的射频场的倏逝波分量.两个不同的标准表面射频线圈的MRI扫描实验表明, 小水膜仿体在施加MIL后可以将矢状面图像信噪比提高约200%, 大水膜仿体在施加MIL后可以将冠状面图像信噪比提高约58%.仿真和MRI图像结果均表明了所设计的MIL具有聚焦表面射频线圈磁场强度的能力, 有益于提高MRI的信噪比、空间分辨率和探测深度.

A metamaterial Magneticinductive Lens (MIL) with negative permeability was designed to improve the Signal-to-Noise Ratio (SNR) for ultra-high field Magnetic Resonance Imaging (MRI). The proposed MIL, fabricated on a FR-4 substrate with a thickness of 0.6 mm, consists of a two-dimensional periodic array of 6×6 capacitor-loaded metallic rings. The equivalent magnetic surface plasmons effect would be achieved in the MIL when it is placed between the RF coil and sample. In terms of the electromagnetic field distribution, the scattering parameters and the equivalent permeability, simulated results reveal that the evanescent harmonics could be heightened. In addition, the evanescent harmonics was excited by the RF coils at the Larmor frequency 297.2 MHz. By loading the MIL, the SNR of MRI images is enhanced about 200% in the sagittal images with a small water phantom, and approximately 58% in the coronal images with a large water phantom. Both simulations and MRI experiments clearly demonstrate that the magnetic field of RF coils could be focused by the metamaterial MIL, which is beneficial to improve the SNR, spatial resolution and detecting depth of MRI.