Ultrasonic waveguide applicator arrays for interstitial heating: amodel study

摘要

In this paper we describe an ultrasonic waveguide multiapplicatornarray for interstitial heating. We first discuss the heat generationnterm common for this type of applicator and show that the radius of thenapplicator is the limiting factor in the pattern of heat deposition. Wencarry out finite element analysis simulations of temperature profilesnfor three- and four-applicator array, and we test the simulations bynmeasurements in a large volume tissue phantom. With the positive resultnof this test, we use the simulations to evaluate the size of the heatednvolume for several applicators (three to six) and for various geometriesnof their positioning. We do the simulations for a range of the effectiventhermal conductivity and for two applicator diameters. The volume of thenmedium with temperatures above 42°C was in the 25 to 73 cm5n range. This volume increased linearly with the diameter of thenboundary at the basal temperature. Power required to produce preselectedntemperature elevation increased monotonically with the effective thermalnconductivity. With the 24 mm between the applicators, the array couldnelevate the temperature to the required value up to the 0.030 W/cm/Kneffective thermal conductivity