Research On Application Of Left-Handed Metamaterial In Microwave Hyperthermia

Left-handed metamaterial (LHM) is a kind of artificial dielectric with negative effective permittivity and effective permeability. Owing to its unique electromagnetic properties, LHM can find wide application in many fields such as nondestructive de-tection, microwave device design, invisible cloak design, etc. In recent years, it is found that, thanks to its unique focusing characteristics, LHM also have great applica-tion prospect in microwave hyperthermia. This paper is concentrated on the research on the key problems in microwave hyperthermia based on LHM. The main work and results is as follows:For superficial tumor with large size and complicated shape, a hyperthermia scheme based on flat LHM lens is propsed to carry out joint heating of multiple sources. By theoretical analysis and simulation approach, the condition of realizing joint heating is identified. On this condition, by deploying multiple sources in specific array and properly setting the source-to-lens distance or phases of sources to acquire a heating zone fit to tumor, conformal hyperthermia can be realized.Considering the flat LHM lens is not suitable for superficial tumors occurring in cylindrical tissue, such as neck, leg, etc. we propose a multiple sources joint heating scheme based on cylindrical LHM lens. After a deep analysis on the focusing proper-ties of cylindrical lens, specific microwave sources configuration scheme to realize conformal hyperthermia of superficial tumor is proposed.The composition principle of a low loss LHM structure based on transmission line theory is analyzed in detail. On the basis of parameters optimization, two kinds of LHM structure with low losses are designed to fabricate flat LHM lens with high/low refraction index, respectively. A new LHM lens with cooling functions is designed to solve the problems, including high reflection and concomitant drop in focusing per-formance, created by the water bolus in hyperthermia system. In this design, the water bolus is realized in partial LHM lens structure. As a result, the hyperthermia perfor-mance can be kept when cooling functions is realized.By using the flat lens composied of transmission line LHM structure, a focusing experiment system is constructed. The experimental focusing results of two sources indicate the microwave sources configuration solution in the proposed hyperthermia is effective and feasible. And the advantages of the LHM lens with cooling functions is verified by a simple experimentThen utilizing the lens with high refractive index, a simple microwave hyper-thermia experiment system with a single source is constructed. To some degree, the results of heating a biological tissue sample indicate that the LHM has great potential applications in microwave hyperthermia.