A Comparative Study of Ablation Boundary Sharpness After Percutaneous Radiofrequency, Cryo-, Microwave, and Irreversible Electroporation Ablation in Normal Swine Liver and Kidneys.

PURPOSE: To compare ablation boundary sharpness after percutaneous radiofrequency ablation (RFA), cryoablation (CA), microwave ablation (MWA) and irreversible electroporation (IRE) ablation in normal swine liver and kidney.

MATERIALS AND METHODS: Percutaneous CT-guided RFA (n = 5), CA (n = 5), MWA (n = 5) and IRE (n = 5) were performed in the liver and kidney of four Yorkshire pigs. Parameters were chosen to produce ablations 2-3 cm in diameter with a single ablation probe. Contrast-enhanced CT imaging was performed 24 h after ablation, and animals were killed. Treated organs were removed and processed for histologic analysis with hematoxylin and eosin, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Three readers independently analyzed CT, H&E and TUNEL stained images of the ablation boundary to delineate regions of (1) viable cells, (2) complete necrosis or (3) mixture of viable and necrotic cells which was defined as the transition zone (TZ). The width of TZ was compared across the techniques and organs.

RESULTS: Ablations appeared as non-contrast-enhancing regions on CT with sharp transition to enhancing normal tissue. On TUNEL stained slides, the mean width (μm) of the TZ after MWA was 319 ± 157 in liver and 267 ± 95 in kidney, which was significantly lower than RFA (811 ± 477 and 938 ± 429); CA (452 ± 222 and 700 ± 563); and IRE (1319 ± 682 and 1570 ± 962) (all p < 0.01). No significant differences were observed between the organs.

CONCLUSION: Under similar conditions, the width of the TZ at the ablation boundary varies significantly between different ablation techniques.