카라기난을 이용한 생체모의매질의 제작과 매질 내 온도변화 검출기법에 관한 연구

Abstract

The temperature elevation effect in the dissipative medium depending on the ultrasonic power should be estimated precisely to secure the safety in the developing medical device using ultrasound. However, it is impossible to measure the temperature elevation in human tissue non-invasively, and a tissue mimicking phantom is generally used to verify the temperature elevation caused by ultrasound. In this study, we fabricated a tissue mimicking phantom made of carrageenan gel that has high transparency for visualization as well as the characteristics similar with biological tissues. The acoustic and thermodynamic characteristics of the tissue mimicking phantom were examined for different concentrations of the carrageenan and sucrose. To visualize the temperature elevation in the phantom due to the ultrasound, a thermochromic film with a critical temperature of discoloration was adopted. As the results, by changing the concentration of carrageenan and sucrose, the acoustic attenuation coefficient, the sound velocity and the acoustic impedance could be controlled from 0.445 ~ 0.481 dB/cm/MHz, 1507 ~ 1591 m/s, and 1.55 ~ 1.77 Mrayls, respectively. In the case of thermodynamic characteristics, the thermal conductivity and the specific heat capacity changed in the ranges of 5.06×10-3 ~ 5.71×10-3 W/cm/K and 3551 ~ 4052 J/kg/K, respectively. We succeeded in showing the temperature distribution quantitatively in the phantom by deriving empirically the relationship between the discoloration area and the elevated temperature. As the result of applying the method to the temperature elevation due to focused and planar ultrasound, the temperature of the phantom changed from 26 ℃ to 40 ℃ by the focused ultrasound, and from 26 ℃ to 31 ℃ by the planar ultrasound. From these results, it can be confirmed that the temperature distribution in the carrageenan phantom could be visualized and obtained quantitatively by using the suggested method. Moreover, this results corresponded with the theoretical calculations by using the bio-heat transfer equation(BHTE), and the validity of the proposed temperature visualization and quantification techniques were confirmed. It is expected that the temperature elevation effect in human body due to the ultrasound could be estimated non-invasively with the method suggested in this study.