Control of the magnetic near-field pattern inside MRI machine with tunable metasurface

Abstract

The metasurfaces concept allows developing and advancing the methods to control the near electromagnetic field pattern in almost arbitrary ways. This property, among other things, is making them an essential platform for useful applications, for example, to improve magnetic resonance imaging (MRI) characteristics through local enhancement of the transmit efficiency as well as the increase in the sensitivity of the radio frequency coils. In this letter, we investigate a compact metasurface-based resonator formed as an array of parallel copper wires with capacitive loads printed on the low-loss dielectric substrate. We demonstrate how to tailor the spectral characteristics of the metasurface eigenmode as well as to control precisely the homogeneity of the near-field pattern by changing the effective capacitance of the structure. We experimentally verify that by tuning the metasurface characteristics, it is possible to decrease the excitation power needed to provide the optimal transmit efficiency of the body coil, thus making the MRI procedure safer. Our approach offers a practical method to control the electromagnetic near-field pattern and has potential in various applications, such as MRI and wireless power transfer.