A comparison of microwave ablation and bipolar radiofrequency ablation both with an internally cooled probe: results in ex vivo and in vivo porcine livers

Abstract

Purpose: The purpose of this study was to compare the effectiveness of microwave (MW) ablation and radiofrequency (RF) ablation using a single internally cooled probe in a hepatic porcine model.

Materials and methods: In the ex vivo experiment, MW ablations (n=40) were performed with a 2450MHz and 915MHz needle antenna, respectively at 60W, 70W power settings. Bipolar RF ablations (n=20) were performed with a 3-cm (T30) and 4-cm (T40) active tip needle electrodes, respectively at a rated power 30W and 40W according to automatically systematic power setting. In the in vivo experiment, the 2450 MHz and 915 MHz MW ablation both at 60W and T30 bipolar RF ablation at 30 W were performed (n=30). All of the application time were 10 min. Long-axis diameter (Dl), short-axis diameter (Ds), ratio of Ds/Dl, the temperature data 5mm from the needle and the time of temperature 5mm from the needle rising to 54°C were measured.

Results: Both in ex vivo and in vivo models, Ds and Dl of 915 MHz MW ablations were significantly larger than all the RF ablations (P<0.05); the Ds for all the 2450MHz MW ablations were significantly larger than that of T30 RF ablations (P<0.05). 2450MHz MW and T30 RF ablation tended to produce more elliptical-shaped ablation zone. Tissue temperatures 5mm from the needle were considerably higher with MW ablation, meanwhile MW ablation achieved significantly faster rate of temperature rising to 54°C than RF ablation. For in vivo study after 10 min of ablation, the Ds and Dl of 2450 MHz MW, 915 MHz MW and Bipolar RF were 2.35±0.75, 2.95±0.32, 1.61±0.33 and 3.86±0.81, 5.79±1.03, 3.21±0.51, respectively. Highest tissue temperatures 5mm from the needle were 80.07±12.82°C, 89.07±3.52°C and 65.56±15.31°C and the time of temperature rising to 54°C were respectively 37.50±7.62s, 24.50±4.09s and 57.29±23.24s for three applicators.

Conclusion: MW ablation may have higher potential for complete destruction of liver tumors than RF ablation.