A Dual-Mode Coaxial Slot Applicator for Microwave Ablation Treatment

Recent developments of microwave ablation systems pursue a treatment monitoring technique in order to provide a curative therapy option for cancer patients. In this paper, such an approach is realized by a dual-mode microwave applicator that enables the permittivity extraction of the tissue surrounding the applicator during the intervention. The additional sensing mode facilitates the positioning of the applicator by detecting dielectric contrasts to indicate the presence of tumors as well as providing tissue state information during the thermal therapy. This feature is based on a one-port calibration scheme which is applied before each intervention. Measurements of various sodium chloride solutions reveal a measurement error below 4%. Furthermore, ex-vivo liver ablation experiments with the input powers of 10 and 20 W are performed to evaluate the treatment monitoring feature and ablation efficacy. A significant permittivity drop down to 82% of the initial permittivity value can be observed after 2 min of ablation. The achieved ablation zones show a preferably spherical shape and clinically relevant volumes with a maximum size of 7.1 cm(3).