Ultrasonic heating with waveguide interstitial applicator array

Ultrasound interstitial applicators can be used for heating tumors near air and bone interfaces, where use of noninvasive ultrasound methods becomes difficult. We describe in this paper an ultrasonic waveguide three-applicator array for interstitial thermotherapy. We first discuss the temperature distribution and the pattern of heat deposition using the effective thermal conductivity equation. This equation is used then for finite element analysis of temperature modeling. We discuss heating in porcine brain tissue and present results with the array in a large volume tissue phantom. Simulation results agreed well with the experiment. The average difference between measured and simulation temperatures was <0.4°C, less than the precision of temperature determination. Further modeling of temperature distribution in the human brain was based on the above simulations. We show that the arrays can be useful for thermotherapy in tissues with an appropriate choice of physical parameters of the applicators