FEA computations of interstitial applicator heating patterns based on power measurements

The pattern of power deposition from interstitial devices governs in principle the heating pattern. In reality, the heating pattern will also depend on placement of applicators with respect to the surface at ambient temperature and also on locally different properties of the heated medium. This presentation gives results of computations of temperature distribution in heating with four ultrasound or microwave (MW) applicators. The computations are based on a measured power deposition from the applicators. Local microstructures of the medium are represented as heat sinks. We show that the ultrasound devices produce more uniform and deeper heating with the same length of radiating parts. Heating patterns in three dimensions from our computations lack the symmetry of the measured power, an effect especially dramatic for the microwave applicators. The type of computations presented here gives details of heating patterns unavailable from power measurements in phantoms. We conclude that the computations should form an integral part of verification of an instrumentation performance.