Computer modeling and ex vivo experiments with a (saline-linked) irrigated electrode for RF-assisted heating

Area of Science:

• Biomedical Engineering
• Medical Physics
• Surgical Technology

Background:

• Externally irrigated radiofrequency (RF) electrodes are used for tumor ablation and surgical coagulation.
• No prior mathematical models existed for these electrodes, particularly concerning the saline layer's role.

Purpose of the Study:

• To develop and validate a mathematical model for externally irrigated RF electrodes.
• To investigate the electrical and thermal performance, focusing on the saline layer's impact.

Main Methods:

• Numerical modeling of the TissueLink DS3.0 device, incorporating saline irrigation and heat convection.
• Ex vivo experiments using bovine hepatic tissue to parameterize and validate the model.
• Comparison of simulated 60°C isotherms with experimental tissue whitening.

Main Results:

• Model accurately predicted lesion depth (2.4 mm) and showed good agreement with experimental data.
• Simulations indicated the saline layer is crucial for thermal lesion formation, with RF power dominating near the electrode and conduction by heated saline at a distance.
• The model confirmed saline did not boil and highlighted the importance of including heat convection for accurate thermal predictions.

Conclusions:

• The developed model successfully replicates the thermal performance of irrigated RF electrodes.
• The model elucidates the interplay between impedance, electrode depth, and the saline layer.
• It provides a mechanistic understanding of thermal lesion creation by these devices.