Objective: To investigate the performance of microwave ablation using an internally-cooled antenna in ex vivo and in vivo porcine liver model.

Methods: Microwave ablations were performed in ex vivo and in vivo porcine livers with a 1.9 mm-diameter 2450 MHz microwave antenna. Four power settings (50W, 60W, 70W, 80W) were used in this study, application time was fixed at 10 minutes. Diameters of the coagulation zone were observed on gross specimens.

Results: Excessive elongation of coagulation along the shaft was not encountered in all ablations. An arrow-shaped charring was observed. As the power increases, the long-axis coagulation diameter for in vivo liver increased significantly (P< .05). The short-axis coagulation diameter for in vivo liver was significantly smaller than that for ex vivo liver (P< .05) but not statistically different among the four power settings. After 10 minutes of ablation at 80W, the short-axis and long-axis coagulation diameter for in vivo liver was 2.37cm ±0.10, 4.92 cm ±0.15 respectively.

Conclusions: The internally-cooled antenna may be advantageous to minimize collateral damages. But as it fail to obtain a large enough coagulation diameter, multiple overlapping ablations are still needed for most tumors.