NUMERICAL EVALUATION OF HEAT CLEARANCE PROPERTIES OF A RADIATIVELY HEATED BIOLOGICAL TISSUE BY ADAPTIVE GRID SCHEME

Abstract

In this article we numerically examine the heat transport in a biological tissue heated by microwave radiation. Such heating of biological tissue is carried out in treatment of cancer by hyperthermia. To understand the effects of hyperthermia, it is necessary to establish the relationship between the vascular structure of the heated tissue and both the gross temperature distribution and local temperature fluctuations that can occur near thermally significant vessels in it. We employ the adaptive grid numerical schemes with body-fitted coordinates to examine the heat transfer problem. We consider two different configurations of thermally significant blood vessels (artery/vein) present in the tissue. Energy equations, previously derived from volume-averaging methods, are modified for several vascular geometries and are used to model heat transfer in tissue with vessels occurring singly or in countercurrent pairs. As a fully three-dimensional treatment is computationally expensive, we use an approximate technique. In this technique the governing equations are first solved in the axial direction to determine magnitude and location of maximum temperature in the tissue. Next at this location, in a cross section normal to the axial direction, a two-dimensional formulation for temperature distribution in the tissue is solved. It is demonstrated that the adaptive grid numerical schemes can be effectively used for the two-dimensional problem of paired vessel configuration. From the results of the numerical model, it is possible to predict whether the temperature of the radiativety heated tissue volume is raised to a desired level or not.