Pork, porcine kidneys and livers preparation: the experiments were carried out in accordance with the guidelines issued by the Ethical Committee of Huazhong University of Science and Technology for the National Key R&D program of China (Grant No. 2017YFB1303100).
Ultrasound-guided RFA: An ultrasound probe (type VC2-9) was used to exam the profile of target tissue. If possible, computed tomography (CT) is suggested for the reconstruction of the 3D profile. According to the morphologic appearance of the target tissue, the insertion position of electrode and the expanded length of sub-electrode is then determined. After that, the position of ultrasound probe should be adjusted to make sure that the insertion position and the whole insertion trajectory of electrode could be observed during the RFA (that is to say, in-plane operation is suggested in the experiment). Before insertion, sub-electrodes are withdrawn in the electrode. Subsequently, the electrode punctures tissue and penetrate to the target tissue under the guidance of ultrasound imaging. After the electrode is precisely deployed, sub-electrodes are expanded as planned. Then, a rational ablation power is selected for RFA. By observing the shape and size of the brightened area (ensure that a safety margin of 5-10 mm exists), the ablation is ceased accordingly. Finally, the electrode is withdrawn and removed.