Mathematical model and experimental study on transient temperature profiles around a cylindrical heat source inside an in vitro tissue

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.In treatment of tumor by hyperthermia, the temperature profile around the heat source is the major factor influencing the effect of hyperthermia. In this study, a mathematical model of the transient temperature profiles around a cylindrical heat source inside an in vitro tissue has been developed. Experiments with an in vitro pork liver have been conducted to study the change of liver temperature around a nickel­-chromium alloy wire heated by direct current at fixed power. Computer simulation of the mathematical model can be used to help doctors to predict the change of temperature profiles in the tissue during thermal therapy The results show that liver temperature near the heating source can be controlled in a desired range for hyperthermia, say, 45-70 "C, by a simple on-off control of the power of heat source. For example, heating power is switched on for 300 seconds firstly, then off and on each for 50 seconds repeatedly. The results also show that as the distance from the heat source increases, the tissue temperature decreases, and the magnitude of temperature oscillation due to power off and on decreases too. There are two parameters, thermal conductivity (k) and heat transfer coefficient (h), in the mathematical model. It has been found that there exists a zone, in the range of 0.66≤k≤0.74 W/m-K and 130≤h≤155 W/m2-K, where the average error between mathematical model and experimental model is less than 2.40"C. When temperature dependency of thermal conductivity, k=0.4981+0.0008T, is considered, there exists a minimum of average error of 2.59 "C at h 210 W/m2-K. However, for a wide range of heat transfer coefficient between !50 and 280 W/m-K, the average error is less than 3"C.