Development and analysis of a microwave direct contact water-loaded box-horn applicator for therapeutic heating of bio-medium

Abstract

A novel, potential and efficient microwave direct contact hyperthermia applicator referred to as water-loaded box-horn for therapeutic heating of bio-medium is designed and developed at 915 and 2450 MHz. Also, theoretical expressions for fields in bio-medium as produced by a direct contact box-horn applicator have been derived using plane wave spectral technique. The box-horn is a special type of dual mode horn antenna which supports TE10- and TE30-modes. Therefore, the aperture field distribution over the H-plane of the box-horn is nearly uniform which prevents steep temperature gradients in the heating medium. Water-loading of the box-horn provides a better impedance match to the bio-medium and hence better coupling of microwave energy into bio-medium. Also, it reduces the size of box-horn applicator considerably. The SAR distributions in bio-medium in direct contact with water-loaded box-horn have been computed theoretically with the developed analytical model and measured experimentally with the help of Agilent/HP vector network analyzer (8714 ET) at 915 and 2450 MHz. The theoretical and experimental results for SAR are in nearly in agreement with each other. It is investigated that higher penetration depth, lower power absorption coefficient and higher half-power width/depth or lower resolution in heating medium are found for box-horn designed at 915 MHz in comparison to those for box-horn designed at 2450 MHz.