Percutaneous radiofrequency tissue ablation: does perfusion-mediated tissue cooling limit coagulation necrosis?

Area of Science:

• Hepatobiliary Surgery
• Interventional Radiology
• Oncology

Background:

• Radiofrequency (RF) ablation is a key technique for treating liver tumors.
• Observed differences in RF ablation efficacy between in vivo and ex vivo studies suggest a role for perfusion.
• Perfusion-mediated tissue cooling is hypothesized to limit coagulation necrosis during RF ablation.

Purpose of the Study:

• To investigate whether decreased hepatic perfusion during RF ablation can explain reduced coagulation in vivo.
• To determine the impact of reduced blood flow on RF ablation efficacy in liver tissue.

Main Methods:

• RF ablation was performed in vivo on porcine liver with and without vascular occlusion (portal vein, celiac artery, hepatic artery).
• Vasopressin infusion was used to modulate hepatic perfusion during RF ablation.
• RF ablation was also performed ex vivo on calf liver and intraoperatively on human liver metastases, with and without portal inflow occlusion.

Main Results:

• Portal venous occlusion significantly increased coagulation necrosis diameter in porcine liver compared to normal blood flow (2.9 cm vs 2.4 cm).
• Intraoperative RF ablation in patients showed larger coagulation diameters for metastases treated with portal inflow occlusion (4.0 cm vs 2.5 cm).
• Thermometry confirmed increased temperatures at a distance from the electrode during portal inflow occlusion.

Conclusions:

• Perfusion-mediated tissue cooling limits the extent of coagulation necrosis achieved with RF ablation.
• Reducing hepatic blood flow during RF application enhances coagulation necrosis in both animal models and human liver metastases.
• Strategies to decrease perfusion can improve the efficacy of RF ablation for liver malignancies.