A VARIABLE MICROWAVE ARRAY ATTENUATOR FOR USE WITH SINGLE-ELEMENT WAVE-GUIDE APPLICATORS

The effectiveness of hyperthermia treatments is often limited by tempe rature inhomogeneity that arises in the treatment field due to variabl e tissue properties and blood flow. Moreover, blood flow can change du ring a treatment, leading to the formation of hot and cool areas even if the initial temperature distribution is uniform. A variable microwa ve array attenuator has been constructed, that will enable the field p atterns of single element microwave waveguide hyperthermia applicators to be altered during treatment, to improve temperature homogeneity. T he coupling bolus was designed with an array of individually controlle d elements, each filled with a microwave absorbing saline solution. Ad ditions or withdrawals of saline are made to alter the power depositio n in a specific area of the treatment field. Thermographic measurement s were made in muscle equivalent phantom materials, with the bolus/wav eguide assembly. Results showed that the variable array attenuator was able to significantly alter the heating pattern of a large waveguide applicator.