Numerical investigation into the enhancement of microwave ablation efficiency by controlling slot design and input power using a dual-slot coaxial antenna.

Abstract

Cancer treatment is performed differently depending on location of the tumor and the patient's condition. Among various cancer treatment techniques, microwave ablation (MWA) is a method that uses temperature elevation as its mechanism. It uses a microwave coaxial antenna (MCA), and microwaves emitted from the MCA are absorbed by the tissue, causing tissue temperature to rise. In this study, the slot design within the MCA was modified, and therapeutic effects of each slot design were analyzed. A dual-slot antenna was selected, and microwave energy absorption and corresponding temperature distribution were analyzed numerically based on length ratio between slots, spacing between slots, and input power. Furthermore, based on this, the Arrhenius damage integral was calculated to quantitatively assess the thermal damage to the tumor and surrounding normal tissue. Finally, thermal damage conditions for dual-slot design and input power were presented, which inflicted thermal damage throughout the entire tumor while simultaneously minimizing thermal damage to surrounding normal tissue. The study confirmed that as the area occupied by the slot increases, the input power required to inflict thermal damage on the entire tumor decreases. The conditions that simultaneously inflicted thermal damage on the entire tumor while minimizing thermal damage to surrounding normal tissue were calculated to be <i>ψ_l</i> = 2.0, <i>l_sd</i> = 1.5 mm and <i>P_in</i> = 16 W. The results indicate that while extending the upper slot enhances the ablation performance, varying the lower slot length does not show a consistent trend, and the therapeutic effect is more sensitive to input power than to geometric modification. At these conditions, the degree of damage to surrounding normal tissue was confirmed to be 62.1%. This suggests that the accuracy and efficiency of future MWA procedures can be improved.