Hyperthermia applicator based on a reentrant cavity for localized head and neck tumors

A new applicator based on a reentrant cavity is proposed for treating localized tumors such as those of the head and neck. In order to effectively heat the localized tumor without causing dissipation of heat into the surrounding normal tissues, the electric field must be localized over the target region. Although a small applicator may produce an appropriate localized electric field, the higher resonant frequency due to downsizing of the equipment results in very poor heating distribution; this occurs due to the changes in electric permittivity and conductivity consequent upon an increase in the resonant frequency. In this article, we introduce a method for reducing the resonant frequency by inserting a dielectric material into the applicator; the efficacy of this method has been determined by calculating the electromagnetic field and heating distribution with the help of the finite element method. By using the proposed applicator, a reduction in the resonant frequency and localized heating over spherical regions 100 mm in diameter can be achieved.