生物组织电特性在体测量微创电极的设计及应用研究

Study on Micro-Invasive Electrode Applied to Bio-Tissue’s Electrical Properties Measuring In-Vivo

根据平行板电容法测量原理,应用矩量法计算极板电荷分布,设计一种用于在体测量的微创探针电极,夹持组织的体积仅有0.8 mm^3。应用有限元法仿真研究微创电极中电场的分布,以证明微创电极能够有效屏蔽边缘效应。按照肿瘤生长时间将裸鼠分成3组(7、14、21 d),每组10只。在0.5～5 MHz频率范围内,分别测量在体和离体条件下,3组裸鼠的乳腺癌肿瘤组织和正常组织的电阻抗和阻抗角,计算得到相应的电特性参数(电导率和介电常数);并且在1、3、5 MHz这3个频率点,在体测量肿瘤组织、肌肉组织和脂肪组织的电特性参数。结果表明,在0.5～5 MHz频率范围内,在体肿瘤的电导率和介电常数随肿瘤生长时间的增长而变大,在体肿瘤与离体肿瘤的电特性参数有显著差异;在所测的3个频率点中,肿瘤组织与肌肉组织和脂肪组织的电特性参数分别存在显著差异。所设计的微创探针电极可实现微创在体测量的目标。

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 mm^3. 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.