Assessment of Various Types of US Findings after Irreversible Electroporation in Porcine Liver: Comparison with Radiofrequency Ablation

Abstract

PurposeTo assess various ultrasound (US) findings, including B-mode, shear-wave elastography (SWE), and contrast-enhanced US, in accurately assessing ablation margins after irreversible electroporation (IRE) based on radiologic–pathologic correlation, and to compare these findings between IRE and radiofrequency (RF) ablation. Materials and MethodsIRE (n = 9) and RF ablation (n = 3) were performed in vivo in three pig livers. Each ablation zone was imaged by each method immediately after the procedure and 90 minutes later. Ablation zones were evaluated based on gross pathologic and histopathologic findings in samples from animals euthanized 2 hours after the last ablation. The characteristics and dimensions of the histologic ablation zones were qualitatively and quantitatively compared against each US finding. ResultsIn B-mode US at 90 minutes after IRE, the ablation zones appeared as hyperechoic areas with a peripheral hyperechoic rim, showing excellent correlation (r2 = 0.905, P < .0001) with gross pathologic findings. SWE showed that tissue stiffness in the IRE ablation zones increased over time. Contrast-enhanced US depicted the IRE ablation zones as hypovascular areas in the portal phase, and showed the highest correlation (r2 = 0.923, P < .0001) with gross pathologic findings. The RF ablation zones were clearly visualized by B-mode US. SWE showed that tissue stiffness after RF ablation was higher than after IRE. Contrast-enhanced US depicted the RF ablation zones as avascular areas. ConclusionsIRE and RF ablation zones can be most accurately predicted by portal-phase contrast-enhanced US measurements obtained immediately after ablation.