915MHz microwave ablation with implanted internal cooled-shaft antenna: initial experimental study in in vivo porcine livers.

PURPOSE: To explore a preferred power output for further clinical application based on the ablated lesions induced by the four power outputs of 915 MHz microwave in experimental study of in vivo porcine livers.

MATERIALS AND METHODS: A KY 2000-915 microwave ablation system with an implanted 915 MHz internal cooled-shaft antenna was used in this study. A total of 24 ablations were performed in eight in vivo porcine livers. The energy was applied for 10 min at microwave output powers of 50 W, 60 W, 70 W, and 80 W. Long-axis and short-axis diameters of the coagulation zone were measured on all gross specimens.

RESULTS: The shapes of the 915 MHz microwave ablation lesions were elliptical commonly. As the power increased, the long-axis and short-axis diameters of the coagulation zone had a tendency to rise. But the long-axis diameter of the ablated lesion at 50 W was not significantly smaller than that of the ablated lesion at 60 W (P>0.05) and there were no statistical differences in short-axis diameters of the ablated lesion among the three power outputs of 60 W, 70 W and 80 W (P>0.05). After 10 min irradiation of 60 W, the long-axis and short-axis diameters of the coagulation zone were 5.02±0.60 cm and 3.65±0.46 cm, respectively.

CONCLUSIONS: For decreasing the undesired damages of liver tissues along the shaft and the number of antenna in further clinically percutaneous microwave ablation treatment, the power of 60 W may be a preferred setting among the four power outputs used in present study.