Irreversible electroporation ablation with bipolar electrodes: ultrasound findings of ablation zones

Background This study aimed to explore the ultrasound and contrast-enhanced ultrasound (CEUS) imaging characteristics and dimensions of ablation lesions after irreversible electroporation of the swine liver and to determine which imaging modality is more suitable for post-procedural follow-up by correlating imaging findings with histopathology. Materials and methods Irreversible electroporation procedures were conducted on three swine with single bipolar electrodes. All procedures were carried out after laparotomy. Twenty-four ablation zones were created under ultrasound guidance. Ultrasound and CEUS evaluations were performed immediately and 48 h after irreversible electroporation. Liver specimens were harvested 48 h after irreversible electroporation for histopathological analysis. Results The ablation area appeared as a hypoechoic, well-defined lesion on ultrasound and showed no enhancement on CEUS immediately after irreversible electroporation. At 48 h, the ablation zone appeared as an inhomogeneous hyperechoic area with a hyperechoic margin and blurred boundaries on ultrasound. CEUS clearly delineated the boundary of the ablation zone and demonstrated centripetal enhancement. The dimensions of the ablation area measured on CEUS 48 h after irreversible electroporation showed the highest correlation with the pathologic ablation zone size (length: r = 0.909, width: r = 0.942, p < 0.001), whereas ultrasound measurements showed the lowest correlation (length: r = 0.676, width: r = 0.842, p < 0.001). Conclusions Compared with conventional ultrasound, CEUS can accurately measure the dimension of the ablation area, especially 48 h after irreversible electroporation.