EFFECT OF FREQUENCY AND CONDUCTIVITY ON FIELD PENETRATION OF ELECTROMAGNETIC HYPERTHERMIA APPLICATORS

The field penetration of electromagnetic hyperthermia applicators in 2 .5-29 g l-1 saline (NaCl) solutions over a range of frequencies is inv estigated. Calculated field penetration based on the current-element m ethod agrees well with measurement at frequencies above about 100 MHz, but at lower frequencies measured field penetration becomes progressi vely less than calculated as conductivity is reduced. Experimental res ults and finite-difference time-domain (FDTD) method modelling show th at the electromagnetic field produces circulating currents. The effect of these circulating currents on the heating pattern of the applicato rs should be considered when planning hyperthermia treatment.