A set of helical microwave antennas was designed to investigate their potential use in thermal therapy of Barrett's oesophagus. The antennas had a diameter of up to 3.3 mm and various lengths between 20 and 37 mm; these were designed to operate at 915 MHz. Sets of polytetrafluoroethylene (PTFE) formers were constructed to improve the repeatability and reproducibility of the helix manufacture. Small diameter copper wire was Wound over the formers and connected to the coaxial cable at the inner and outer conductor junctions. The power deposition profiles of the antennas were measured in a muscle-equivalent phantom using an infrared camera. The effects of antenna length and coil spacing were characterized. It was observed that uniform temperature profiles along the antenna length were achieved with a length of wire of 99 mm +/- 2 mm. The effective heating length (length of the antenna that exhibits >50% of the maximum temperature rise) was comparable to the antenna length. The radial penetration depth of 50% of the antenna surface temperature for the Optimum 20 mm antenna was 2.5 mm from the antenna outer surface.

Miniature helical applicators were designed to operate at 915 MHz, to investigate their potential use in the hyperthermic treatment of Barrett's oesophagus. Heating patterns were studied within a muscle-equivalent phantom using a thermographic camera. The results show that the spacing between the turns of the coil and the insertion depth of the applicator into the phantom significantly influence the microwave heating pattern.

The aim of this project was to produce microwave phantoms for testing a microwave technique for treating oesophageal malignancies. The microwave phantoms must respond in the same manner as living tissue would when microwaves are applied. The relative permittivity and electrical conductivity must be known in order to match the phantom to the specific tissue being investigated. This paper describes the apparatus developed specifically for this purpose. The apparatus consists of a scalar network analyser with the test material constrained inside the line with a short circuit to reflect the signal back to the analyser. The reflected scalar data gives enough information to allow the relative permittivity and the electrical conductivity to be calculated. Experimental data were compared to standard reference materials. This experimental set-up provides the required dielectric information over a frequency range of 0.8 to 2.5 GHz.