SPATIAL TEMPERATURE CONTROL WITH A 27 MHZ CURRENT SOURCE INTERSTITIALHYPERTHERMIA SYSTEM

Purpose: This article gives an overview of the properties of a 27 MHz current source interstitial hyperthermia system, affecting temperature uniformity. Methods and Materials: Applicators can be inserted in sta ndard flexible afterloading catheters. Maximum temperatures are measur ed with seven-point constantan-manganin thermocouple probes inside eac h applicator, Temperature can be controlled automatically using a simp le control algorithm, Three-dimensional power absorption and thermal m odels for inhomogeneous tissues are available to optimize applicator g eometry and phase configuration, Properties of the interstitial heatin g system have been verified both in phantom experiments and in in vivo treatments of rhabdomyosarcomas implanted in the flank of a rat. Resu lts: An experiment with four electrodes in one catheter proves that lo ngitudinal control of the specific absorption rate (SAR) is feasible, Local cooling applied by cold water circulation through a catheter per pendicular to the afterloading catheter could be compensated by indepe ndent control of electrode power, Furthermore, comparison of two diffe rent phase configurations using four dual electrode applicators shows that the SAR distribution can be manipulated significantly, utilizing the phase of the electrodes. Finally, the temperature can be controlle d safely and model calculations are in fair agreement with the measure ments. Conclusions: The features of the 27 MHz current source intersti tial hyperthermia system enable spatial temperature control at approxi mately 1.5 cm, Copyright (C) 1997 Elsevier Science Inc.