Measurement of Intrahepatic Pressure during Microwave Ablation in an Ex Vivo Bovine Liver Model

Background/Aims: We experimented with different ablation methods and two types of microwave antennas to determine whether microwave ablation (MWA) increases intrahepatic pressure and to identify an MWA protocol that avoids increasing intrahepatic pressure. Methods: MWA was performed using either a single-step standard ablation or a stepwise increment ablation paired with either a 16-gauge (G) 2-cm antenna or a 14G 4-cm antenna. We compared the maximum pressures and total ablation volumes. Results: The mean maximum intrahepatic pressures and ablation volumes were as follows: 16G single-step: 37 +/- 33.4 mm Hg and 4.63 cm(3); 16G multistep: 31 +/- 18.7 mm Hg and 3.75 cm(3); 14G single-step: 114 +/- 45.4 mm Hg and 15.33 cm(3); and 14G multistep: 106 +/- 43.8 mm Hg and 10.98 cm(3). The intrahepatic pressure rose during MWA, but there were no statistically significant differences between the single and multistep methods when the same gauge antennae were used. The total ablation volume was different only in the 14G groups (p<0.05). Conclusions: We demonstrated an increase in intrahepatic pressure during MWA. The multistep method may be used to prevent increased intrahepatic pressure after applying the proper power.