Optimization of three layer tapered coaxial line applicator for cancer thermothrapy by impedance matching of transition layer sections

The structural optimization is presented for a coaxial line applicator for the liver cancer thermotherapy. Currently used applicators are slot type antennas made from commercially available semi rigid cables, therefore the impedance matching between an applicator and a heated liver is not ensured. A novel applicator structure is presented by introducing the impedance matching sections between the radiation part and the feeding coaxial line. Scattering parameter S₁₁ is improved from - 9.82 dB to - 18.6 dB at 2.45 GHz by making proper selection of the inserted dielectric materials and optimizing the geometries of matching layers at 2.45 GHz. Prototype applicators are developed and measured with a raw liver of beef and dimethyl sulfoxide (DMSO) by using the vector network analyzer (VNA). The measured results reveal that the impedance matching is improved and that DMSO can be used as a phantom material of liver.