Design of Hemispherical Radio Frequency (RF) Capacitive-type Electrode Free of Edge Effects for Treatment of Intracavitary Tumors

A new hemispherical electrode to heat oral cavity cancer is proposed. The electrode does not produce a hot spot around its edge, a feature that usually arises when using radio frequency (RF) capacitive-type heating. The hemispherical electrode was designed by computer simulation using a 3-D finite element method. To assess its practicality and effectiveness, we built a prototype hemispherical electrode and evaluated its heating characteristics by phantom experiments. The heating effects on the phantom were measured by thermography. The concave phantom surface in contact with the hemispherical electrode showed a uniform increase in temperature, with no obvious edge effect. The proposed electrode allows non-invasive RF capacitive-type heating for intracavity tumors that was not previously considered possible, and should contribute to the multidisciplinary treatment of intracavity tumors.