Pulse-power integrated-decay technique for the measurement of thermal conductivity

A pulse-power integrated-decay technique for the measurement of thermal conductivity of biological tissues is presented. A self-heated thermistor probe is used to deliver heat and also to measure the temperature response. Three-dimensional finite element analyses are used in this paper to design and optimize the technique. The thermal conductivity measurements from the computer simulations were in close accordance with the experimental data. An empirical calibration process, performed in glycerol and agar-gelled water, provides accurate thermal conductivity measurements. An accuracy analysis evaluated multiple experimental protocols using three solutions of known thermal properties. The results indicate that the thermal decay technique protocol had better accuracy than the constant temperature heating techniques. In vitro measurements demonstrate the variability of tissue thermal conductivity, and the need to perform direct measurements for tissues of interest. The factors that may introduce error in the experimental data are (i) poor thermal/physical contact between the thermistor probe and tissue sample, (ii) water loss from tissue during the course of experimentation and (iii) temperature stability.