Experimental study of coaxial cable antenna with a ring slot for radiofrequency thermal ablation

Radiofrequency thermal ablation (RlA) is becoming one of the treatment for small but inoperable tumors of the liver, disk, prostatomegaly, and Parkinson's disease, as one of the microwave hyperthermias. Especially, it provides a safe and effective option for patients with inoperable or recurrent liver cancer who have failed to respond to conventional methods such as percutaneous ethanol injection (PEI) and transcatheter arterial chemoembolization (TACE). In this paper, we designed the semi-rigid coaxial cable antenna with a ring slot for RTA applicator. To optimize the maximum output of radiation at 2450 MHz, we simulated the antenna using electromagnetic simulation tools HFSS program and analyzed the return loss and the electric field E/sub tot/ at the near-field region by changing the length L/sub ts/ and the width W/sub st/ of a slot. Here, the semi-rigid coaxial cable used is UT 47-TP (Micro-Coax Inc.) which is constructed from a silver-plated copper weld (SPCW) center conductor, a solid PTFE dielectric and a tin-plated copper outer conductor. As a result of experiment, we could obtain the return loss of -29.786 dB at 2450 MHz only when the antenna is placed between two blocks of a pig's liver and the length L/sub st/ and the width W/sub st/ of slot were 6 mm and 2 mm, respectively. The measurement results agreed with the simulation results well, therefore, this coaxial cable antenna with a ring slot can be used very usefully as the applicator for RTA.