|Budget Amount *help
¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1992 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1991 : ¥1,700,000 (Direct Cost : ¥1,700,000)
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.