Theoretical evaluation of the treatment effectiveness of a novel coaxial multi-slot antenna for conformal microwave ablation of tumors

Microwave ablation (MWA) is a form of thermal therapy that uses the heating effects of electromagnetic waves in the microwave energy spectrum to kill undesired or diseased tissues. Slot coaxial antennas are the most popular antennas used in MWA due to their minimal invasiveness and low cost. MWA with slot coaxial antenna has been proven to be very promising for the treatment of hepatic tumors, but the residual 'tail' seen in many of the specific absorption rate (SAR) patterns inevitably damages surrounding healthy tissues. This is because a treatment that fully conforms to the shape of liver tumor is difficult to achieve with conventional MWA antennas even with current optimization strategies. For the first time, we report a novel design for a coaxial antenna with greatly increased possibility of conformal treatment, a coaxial multi-slot antenna with multiple, preoperative, adjustable, slots for conformal microwave ablation. Theoretical simulations revealed that our coaxial multi-slot antenna could greatly decrease over-treatment compared with the conventional coaxial-slot antenna. Additionally, the coaxial-slot antenna with ten slots generates the smallest over-treatment region for spherical tumors, the most common hepatic tumor shape. For tumors with non-spherical shapes, optimal treatment could be routinely accomplished by selecting coaxial-slot antennas with different numbers of slots.