Radiofrequency ablation of rabbit liver: Correlation between dual CT findings and pathological findings

Purpose: To present the time-related imaging findings and correlative pathologic findings of radiofrequency pulse-irradiated regions of the liver. Materials and Methods: Radiofrequency (RF) ablation was performed in 22 rabbit livers with 15-gauge RF probes inserted percutaneously. Regions were imaged with dual-phase CT at 3 days(n=6), 2 weeks (n=6), 4 weeks (n=6), and 12 weeks (n=4) after RF ablation. Results: At 3 days, the regions showed a two-zone structure on plain CT and peripheral enhancement. The regions presented a three-zone structure on pathological study. Hepatocytes appeared as acidophilic bodies, and nuclei were pyknotic at the inner necrotic zone. The middle whitish zone showed enlarged sinusoids. The marginal zone was a regenerative band. At 2 weeks, the two-zone structure was obscured on unenhanced CT. The region showed a two-zone structure on pathological study. At the inner zone, acidophilic degeneration had progressed, however, cell structure remained. The marginal zone showed fibrous tissue bundles. At 12 weeks, the region was obscured on plain CT. Nuclei and cell structures had disappeared almost completely at the inner zone. Collagen fiber had replaced the marginal zone. Conclusion: Zone structural CT findings reflect the pathological findings and time-related changes after RF ablation. Peripheral enhancement in the arterial phase reflects the granulation tissue layer, and its time-related decrease reflects replacement by fibrous tissue.