THE THEORETICAL AND EXPERIMENTAL EVALUATION OF THE HEAT-BALANCE IN PERFUSED TISSUE

Accurate treatment planning is necessary for the successful applicatio n of hyperthermia in the clinic. The validity of four different biohea t models or combinations of models is evaluated: the conventional bioh eat transfer equation, the limited effective conductivity model, a mix ed heat sink-effective conductivity model and a discrete vessel model. The heat balance for the heated volume, and especially the ratio betw een conductive heat removal and heat escape through the veins, is diff erent for each of these models. Model predictions were compared with r esults from experiments on isolated perfused bovine tongues. Tongues w ere suspended in a water-filled container and heated by conduction. Th e steady state temperature distribution and heat balance were determin ed at various blood flow rates. Increased blood flow was found to lowe r the mean tissue temperature and to enhance both conductive and venou s heat removal. This result agrees only with the mixed heat sink-effec tive conductivity and the discrete vessel model predictions. At low fl ow rates a modified heat sink term should be used because the venous e fflux temperature was significantly lower than the mean tissue tempera ture.