Axial shifting with a MAPA: thermal effects during hyperthermia

A three-dimensional thermal model of heat transfer in a human limb was utilized to predict the temperature distribution during a hyperthermia treatment with the mini-annular phased-array (MAPA) applicator. Blood-flow variations with time and temperature in the skin and muscle tissues of the limb were subject to the thermoregulatory mechanisms which have been observed in vivo by others. Results of the thermal model computations show that blood-flow thermoregulation in the muscle tissue tends to dominate the thermal pattern. This limits the temperature of the heated normal tissue to a temperature of 42-43 degrees C. However, thermal dose to a nonthermoregulated tumor is very high (<120 thermal equivalent minutes) and the dose to the normal, perfused surrounding tissue is relatively small if the RF energy is focused primarily in the tumor. An empirical model previously presented can be utilized to predict the axial location of maximum energy deposition in the limb during MAPA exposure as a function of limb geometry and composition.<>