1(Institute of Biomedical Engineering, Chinese Academy of Medical Sciences ＆ Peking Union Medical College, Tianjin 300192,China) 2(School of Physics and Electronic Engineering, Tai Shan University, Taian 271000, Shandong, China)
Abstract：According to the principle of parallel plate capacitance method, the charge distribution of the electrode was calculated by the method of moment and a minimally invasive probe electrode was designed for in vivo measurement in this study. The volume of tissue gripped by the probe was only 0.8 mm3. The electric field distribution in the miniature electrode was simulated by the finite element method. It was proved that the minimally invasive electrode can effectively shield the edge effect. Nude mice were divided into 3 groups according to the time of tumor inoculation (7, 14, 21 d), 10 mice in each group. Within the frequency range of 0.5-5 MHz, the electrical impedance and impedance angles of the tumor tissue and normal tissue of mice were measured in vivo and in vitro, and the corresponding electrical properties (conductivity and permittivity) were calculated. The electrical properties of tumor tissue, muscle tissue and adipose tissue were measured in vivo at 1, 3 and 5 MHz. The results showed that the conductivity and permittivity of tumor in vivo increased with the tumor growth in the frequency range of 0.5-5 MHz. There are significant differences in electrical properties between in vivo and in vitro tumor. At the three frequencies measured, there are significant differences in electrical properties between tumor tissue, muscle tissue and adipose tissue. The designed minimally invasive electrode achieves the purpose of minimally invasive in vivo measurement.
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