Saline-linked Surface Radiofrequency Ablation: Factors Affecting Steam Popping and Depth of Injury in the Pig Liver

Summary Background Data: Saline-linked surface radiofrequency (RF) ablation is a new technique for applying RF energy to surfaces. The surface is cooled, which prevents charring and results in deeper coagulation. However, subsurface heating may lead to steam formation and a form of tissue disruption called steam popping. We determined parameters that predict steam popping and depth of tissue destruction under nonpopping conditions. A commercially available saline-linked surface RF cautery device (Floating Ball 3.0, TissueLink, Inc.) was used.

Methods: One hundred eighty circular lesions were created varying in lesion diameter, duration, power, and inflow occlusion. Variables affecting popping were determined. Then factors influencing lesion depth were studied at fixed nonpopping diameter/power combinations (1 cm/10W, 2 cm/15W, 4 cm/60W). Tissue viability was determined in selected samples by staining of tissue NADH.

Results: The probability of steam popping was directly related to power level and inflow occlusion, and indirectly related to lesion diameter. Depth of injury under safe nonpopping conditions was directly related to power, lesion size, and inflow occlusion. Maximum depth in excess of 20 mm was achieved using a 4 cm diameter at 60W with inflow occlusion. Microscopy of NADH-stained tissues showed a complete cell killing in the macroscopically visible coagulated area.

Conclusions: Steam popping can be avoided by selecting power level/lesion diameter combinations. Tissue destruction to 20 mm can be safely achieved with short periods of inflow occlusion. The device has promise as a treatment of superficial tumors and close resection margins.