Study of Single- and Dual-Frequency Microwave Ablation Antennas Based on Shorted Helical Slot

We present single- and dual-frequency antennas based on the shorted helical slot in hepatic microwave ablation. The single-frequency antenna is designed by lathing a helical slot on shorted traditional semirigid coaxial cable, which is expected to be operated at the frequency of 2450 MHz, and the dual-frequency antenna is designed with the combination of an annular slot and a helical slot, which can be operated at 915 and 2450 MHz. We use full-wave electromagnetic simulation and transient thermal simulation to analyze the performance of the proposed ablation antennas. Both the proposed antennas are fabricated and used in
ex vivo
ablation experiments at different frequencies with a power level of 23 W for 2 or 5 min. We observe that the proposed single-frequency antenna with helical slot has more concentrated specific absorption rate (SAR) pattern than those antennas with conventional slots does at 2450 MHz, and the dual-frequency one has the capability to control the roundness of ablation zone from 0.34 to 0.63 under the different combination of frequencies and operation times. The proposed microwave ablation antennas are expected to lead to a potential solution of curing the liver cancers with various characteristics.