Microwave ablation with a single small-gauge triaxial antenna: In vivo porcine liver model

Purpose: To evaluate the performance of a 17-gauge triaxial antenna at microwave ablation in an in vivo porcine liver model. Materials and Methods: This study was approved by the institutional animal care and use committee. Thirteen female domestic pigs (mean weight, 45 kg) were used. Ablations were performed with a prototype microwave ablation system and triaxial antenna by using a constant, continuous-wave power of 68 W for 2 (n = 6), 3 (n = 6), 4 (n = 6), 5 (n = 6), 6 (n = 6), 7 (n = 13), 10 (n = 7), and 12 (n = 8) minutes. Animals were euthanized after ablation, livers were removed, and ablation zones were sliced and measured for size and roundness. A mixed linear model with animals modeled as random effects was used to test for significant differences in ablation zone metrics among time groups; post hoc tests were used to detect significant differences between time groups. Results: Mean ablation zone diameters ranged from 2.05 cm +/- 0.23 (standard deviation) at 2 minutes to 2.59 cm +/- 0.53 at 12 minutes. Thirteen (32%) of 40 ablation zones with mean maximum diameters greater than 3.0 cm were observed at the 5-12-minute time groups. No significant differences in ablation zone diameter were observed among all groups (P >.05), but a trend of increasing diameter with time was noted. Mean isoperimetric ratio (a measure of roundness) for all ablation zones was 0.88 +/- 0.02, which indicates minimal heat sinking near vessels. Conclusion: The triaxial microwave ablation system is capable of creating relatively large, circular zones of ablation in minutes with minimal effects from local blood flow. (c) RSNA, 2007.