探头结构对阶跃温升法测量生物组织热物理参数的影响

Effects of Probe Configuration on the Measurement of Bio-tissue Thermal Physical Parameters Using Step-temperature Technique

采用阶跃温升法可以测量生物组织热物理参数。但是,阶跃温升法在推导时认为其测量探头是由单一的热敏材料构成的,探头输入功率在探头中均匀分布。而实际的探头多为复合结构,并且探头输入功率在探头中的分布也是不均匀的。本研究通过构建采用复合结构探头时阶跃温升法的数学模型,并对之进行数值模拟,分析了探头结构对阶跃温升法测量生物组织热物理参数的影响;进而通过对探头温升的稳态分析,阐述了探头参数标定值的物理意义。结果表明,对于复合结构的热敏电阻探头,在对探头半径及探头热导率进行标定后,仍然可以采用阶跃温升法来测量生物组织的热物理参数。

The step-temperature technique can be used to measure bio-tissue thermal physical parameters. During the derivation of the step-temperature technique, the measuring probe was assumed to be made of single thermistor sensing element, and the electrical power was assumed to be uniformly distributed throughout the probe bead. However, the probe bead in reality is made of multi-layer structure, and the electrical power is not uniformly distributed throughout the probe bead. In this paper, a mathematical model is built for the step- temperature technique for multi-layer structure probe bead, and a numerical simulation is made to analyze the effects of probe configuration. The physical meaning of the calibrated values of the probe parameters （bead radius and bead thermal conductivity） is also explained theoretically. The results show that the step-temperature technique is still valid for the measurement of bio-tissue thermal physical parameters for the multi-layer structure thermistor probe bead on condition that the bead radius and the bead thermal conductivity are obtained through pre- calibration.