生物组织阻抗温度特性测试系统的研究

The research of a temperature feature of tissue impedance testing system

肿瘤热疗过程中的温度检测和控制是热疗的关键,但温度的无损检测方法较为缺乏,限制了其发展。文中研究了一种装置测试生物组织电阻抗的温度特性,为基于电阻抗特性的温度无损检测技术提供依据。该装置利用恒温水循环原理对组织进行加热,可使组织受热均匀并且温度易于控制,阻抗测量装置采用四电极法原理,可有效消除接触阻抗和极化效应的影响,提高测量精度。文中还研究设计了用于激励的恒流源发生电路,恒流源的输出阻抗在频率为1 MHz时为212 kΩ,具有很好的恒流特性。基于此系统,对两组新鲜肥肉组织进行了测试,研究了其电阻抗温度特性及频率特性,测试结果表明,离体肥肉组织电阻抗实部随频率升高而降低,虚部先降低后升高,转折频率在80~120k Hz之间;其温度特性表现为：小于53℃时,组织电阻抗随着温度升高呈现较为缓慢下降的趋势,在53~59℃之间,电阻抗以及电阻抗变化系数形成一个突变,表现出组织电阻抗变化的临界特性,这为进一步进行肿瘤热疗过程中基于电阻抗技术的温度无损监控提供了理论和实验依据。

The temperature measurement and control is a key factor to Hyperthermia（HIFU）,but the fast, accurate, low-cost technology real-time detection of the temperature is lacking off. This research developed a device to test the relationship of tissue impedance and temperature, which can provide the basis for temperature detection during HIFU. The tissue was heated by water circulation, of use which the temperature is easy to control and heated homogeneous. The four electrode method was used in this device, which can effectively avoid the contact resistance and polarization effects, etc. A high output impedance constant current source was designed; its output impedance is 212 kΩ at a frequency of 1 MHz. Two fresh fat tissue were tested to obtain the impedance’s temperature characteristic and the frequency characteristic, the frequency characteristics are：the real part of impedance decreases with increasing frequency, the imaginary part decreases and increases with increasing frequency, the transition frequency is between 80~120 k Hz, while temperature characteristics are： when the temperature is less than 53 ℃, tissue impedance presented as the temperature decreases slowly, and during 53~59 ℃, the impedance formed a mutant, showing the critical organizational changes, which provides a theoretical and experimental basis for further hyperthermia process technology based on electrical impedance temperature nondestructive monitoring.