Microwave ablation of the lung: Comparison of 19G with 14G and 16G microwave antennas in ex vivo porcine lung

Background: Percutaneous image-guided thermal ablation has an increasing role in the treatment of primary and metastatic lung tumors. Although microwave ablation (MWA) has emerged advantageous as a new ablation technology, more research is needed to improve it. This study aims to investigate the ablation zone of three microwave antennas in ex vivo porcine lung. Materials and Methods: In the ex vivo standard model and porcine lung model, MWA was performed in three power output settings (50 W, 60 W, and 70 W) for 3, 6, 9, and 12 min using three microwave antennas, with outer diameter of 1.03 mm (19G), 1.6 mm (16G), and 2.0 mm (14G). A total of 108 and 216 sessions were performed (3 or 6 sessions per time setting with the 14G, 16G, and 19G microwave antennas). After the MWA was complete, we evaluated the shape and extent of the coagulation zone and measured the maximum long-axis (along the needle axis; length [L]) and maximum short-axis (perpendicular to the needle; diameter [D]) of the ablation zones using a ruler; subsequently, the sphericity index (L/D) was calculated. The sphericity index can be simplified as long-axis/short-axis. Results: In the ex vivo standard model study, the long- and short-axis diameters and sphericity indices were not statistically different between the 14G, 16G, and 19G groups. In the ex vivo porcine lung study, the long- and short-axis diameters did not differ statistically between the 14G, 16G, and 19G groups (P < 0.05 each). The sphericity index for the 19G microwave antenna was higher than the sphericity indices for the 14G and 16G microwave antennas (P < 0.05); however, the index for the 14G microwave antenna was not statistically different than that for the 16G microwave antenna (P > 0.05). Conclusions: The ablation zone of the 19G antenna was the same as those of the 14G and 16G antennas in vitro. Thus, the 19G antenna may reduce the incidence of complications in lung tumor ablation.