微波透热疗法中用增透介质层提高注入功率的研究

Increasing the transmission power by use of an antireflecting dielectric layer in microwave hyperthermia

应用电磁场理论探讨了频率为2450MHz的平面电磁波垂直射到皮肤-肌肉组织表面上的反射和透射问题.结果表明,43％的能量透入人体组织,57％反射回空气.若在人体表面上放置一层相对介电常数ε_r=7.19、厚度d=10.89mm、天磁性的绝缘介质,从理论上讲可将能量透射系数提高到99.99％.接着引入输入波阻抗的概念,把理论推广到多层媒质的情况.然后,用此理论研究了平面电磁波垂直射到皮肤-脂肪-肌肉三层人体组织模型上的增透问题.显示,只要给出皮肤和脂肪层的厚度,即可从理论上求出使能量透射系数达到99.99％的增透介质层的厚度和相对介电常数.

Reflection and transmission of a plane electromagnetic wave at a frequency of 2450 MHz at normal incidence on skin-muscle surface are studied by the electromagnetic theory. Our results show that only 43% electromagnetic energy is transmitted into the body tissues,and 57% energy is reflected from the body surface back to the air. But by placing a non-magnetic, insulating dielectric layer ( it's relative permittivity εr = 7.19, thickness d=10.89mm)on the body surface, energy transmission coefficient could be enhanced to 99.99%. The concept of input wave impedance is introduced in order to generalize the developed theory to multi-layer medium cases. Lastly, this theory is applied to study how to decreace the energy reflection coefficient of a plane electromagnetic wave incident normally upon the three layers ( skin-fat- muscle)body tissue model.The results show that provided the thicknesses of the skin and fat layer are given, we can evaluate theoretically the thickness and relative permittivity of a dielectric layer that could raise incident wave's energy transmission coefficient to 99.99%.