System Investigation Of Metamaterial For Magnetic Resonance Imaging Application

Metamaterial (MM) is an artificial composited material and it has special electromagnetic properties that are mainly defined by its unique structure but not the composition of material. The unique properties have triggered great interest and many works have been done for the last decades, such as the left-handed materials, superlens, slow wave, tunable electromagnetic devices, and cloaking. Magnetic resonance imaging (MRI) has great applications in brain science, neurophysiology and cognitive neuroscience. This paper aims to study MM lens with negative permeability for its applications in MRI. The following works have been done in the present work:First, we study the transmission model of planar split ring resonator (SRR). Then we proposed a slab MM lens fabricated with singly split ring resonator (SSRR). The homogeneous MM lens with negative permeability is extracted from the theoretical model. Meanwhile, due to the superlensing effect of our MM lens, the tumor in the tissue can be distinguished with high resolution. Our slab MM lens may find application in traditional 1.5 T MRI systems.Second, we propose a cylindrical rolled-up negative permeability MM lens for MRI. The proposed cylindrical MM lens is fabricated by rolling a MM slab (constituted with capacitive-loaded copper split rings) into a tube that resembles a hollow ring. It can focus the field of a magnetic line source, which can increase the penetration depth and improve the sensitivity of a surface coil. The proposed cylindrical MM lens can also improve the discrimination of the signals coming from two independent sources. A clinical experiment is carried out in a General Electric Signa 1.5 T MRI system in order to verify the focusing ability of the proposed device. Anyway, the MM lens can increase the signal, but it cannot suppress the noise. The lens increase the noise in the coil since the noise coming from the lens adds to the noise coming from the phantom. We will optimize the lens in the future work.At the end of this thesis, we summarize all the content and also give the research plan for future.