Irreversible electroporation in porcine liver: Acute computed tomography appearance of ablation zone with histopathologic correlation

OBJECTIVE: The objective of this study was to define acute computed tomography (CT) characteristics of ablation zone created by irreversible electroporation (IRE) in porcine liver, with histopathologic correlation. METHODS: Twenty-three IRE ablation zones were created in 4 Yorkshire pig livers percutaneously under image guidance. A prototype generator was used (Ethicon Endo-surgery, Cincinnati, Ohio). Variable spacing of paired electrodes between 1 and 2.0 cm was used. Contrast-enhanced multiphasic CT scans were obtained. Pigs were killed after 5 to 6 hours for gross pathology sectioning with routine and vital histological stains. Computed tomography images were analyzed using 3-dimensional software, and ablation zone size measured on CT was correlated with pathologically determined size. RESULTS: Nineteen of 19 ablation zones created with up to 1.5-cm spacing showed fusion between individual ablation zones generated by each electrode. Ablation zones were isodense precontrast and hypodense to liver postcontrast, with best delineation in the portal phase. Nine of these had nondistorted circumferential margins on both CT and gross pathology suitable for correlation, and among these, size measurements on CT were closely correlated with pathologically determined ablation zone size. Most importantly, on the delayed venous phase, there is internal enhancement within the ablation zone itself, except for small perielectrode zones that remained hypodense. On histopathology, IRE ablation zones showed preserved microvasculature with congestion of sinusoids, except for small perielectrode zones where coagulative changes were suggested. CONCLUSION: Portal phase contrast-enhanced CT scans correlate well with liver IRE ablation size and shape on histopathology.