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

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 2450 MHz and 915 MHz needle antenna, respectively at 60 W, 70 W 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 30 W and 40 W according to automatically systematic power setting. In the in vivo experiment, the 2450 MHz and 915 MHz MW ablation both at 60 W 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 5 mm from the needle and the time of temperature 5 mm from the needle rising to 54 degrees 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 2450 MHz MW ablations were significantly larger than that of T30 RF ablations (P < 0.05). 2450 MHz MW and T30 RF ablation tended to produce more elliptical-shaped ablation zone. Tissue temperatures 5 mm from the needle were considerably higher with MW ablation, meanwhile MW ablation achieved significantly faster rate of temperature rising to 54 degrees 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 5 mm from the needle were 80.07 +/- 12.82 degrees C, 89.07 +/- 3.52 degrees C and 65.56 +/- 15.31 degrees C and the time of temperature rising to 54 degrees C were respectively 37.50 +/- 7.62 s, 24.50 +/- 4.09 s and 57.29 +/- 23.24 s for three applicators. Conclusion: MW ablation may have higher potential for complete destruction of liver tumors than RF ablation. (C) 2009 Elsevier Ireland Ltd. All rights reserved.