Solid Materials Visualizing the Electromagnetic Energy Absorption Pattern Using a Cloud Point of Nonionic Surface Active Agent

1. 首先，构建了由氦氖激光器、光功率计、数字体温计和个人计算机组成的云点和光衰减随温度变化的测量系统。光衰减测量的动态范围为45 dB，激光功率为2 mw。琼脂凝胶是吸收电磁能量的最常用材料。测定了裸凝胶的光学透明度。琼脂浓度低于2%时，凝胶的透明特性显著提高，但凝胶的机械强度降低。为了进一步提高透明度，在材料中加入甘油，在凝胶中不含表面活性剂的情况下，获得了良好的光衰减效果。在热疗等实验中，幻体的电特性必须与生物组织相同。通过调节盐浓度可以改变材料的导电性。在1%的浓度范围内，除云点降低外，对其光学和机械特性没有影响。光学衰减测量表明，聚丙烯酰胺、kappa-卡拉胶、结冷胶等水凝胶比琼脂凝胶具有更好的透明度。加入离子物质后，后两种材料的机械强度增强，因为它们与基材相互作用形成蛋盒结结构。这种效应在以前的材料中没有发生。加入离子物质后，结冷胶的透明度降低。结果表明，kappa- carragean是最理想的构建立体可视化体模的材料。

1. At first, the measurement system of a cloud point and optical attenuation vs. temperature of the visualizing materials were constructed, which consisted of a He-Ne laser, an optical power meter, a digital thermometer, and a personal computer. The dynamic range of the optical attenuation measurement was 45 dB with the laser power of 2 mW.2. Agar gel is the most popular material in the phantoms absorbing electromagnetic energy. Optical transparency of the bare gel was measured. The characteristics of the transparency increased remarkably at the concentration of the agar below 2 %, though the mechanical strength of the gel was decreased. For further improvement of the transparency, glycerol was added to the material, and good results in optical attenuation were obtained when the surface active agent was absent in the gel.3. Electrical properties of the phantom have to be the same as those of biological tissues in the experiments such hyperthermia. Electrical conductivity of the material could be varied by adjusting the salt concentration. There were no changes in the optical and mechanical characteristics due to adding the salt within the concentration of 1 % except decrease of the cloud point.4. The optical attenuation measurement manifested that the hydrogels such as polyacrilamide, kappa-carrageenan, and gellan gum gels had better transparency than that of the agar gel. The mechanical strength became strong in the last two materials by adding the ionic substances, because they formed a structure of egg-box-junction interacting with the base material. This effect was not occurred in the former materials. The transparency of the gellan gum became lower by adding the ionic substances. From these results, it was concluded in the present study that kappa-carrageenan was the most excellent material for building the solid visualization phantom.