Tech Briefs

Radio-Frequency Ablation of Tissues Using
the ADINA-F Joule Heat Capability

The Joule Heat modeling in ADINA-F is used to solve problems where heating of materials occur due to the existence of an electric current. A common application of this feature is the radio-frequency (RF) ablation of tissues. This is an important medical technique used for the therapy of cardiac arrhythmias and lesions in subcortical structures of the brain. The ablation is carried out delivering a RF current (300 kHz to 1 MHz) through an electrode embedded in the treated tissue. The high current density that appears neighboring the electrode tip induces a volumetric heating due to the Joule effect. Therefore, the temperature of the tissue surrounding the electrode increases uniformly from 37 to above 50 degrees Celsius. Moreover, the temperature of the tissue must never exceed 100 °C to avoid charring and tissue micro-explosions.

The animation depicts a detail of a catheter and electrode assembly. The electrode tip is embedded in the tissue for a 60-second ablation cycle. On top of the tissue there is a blood stream flowing perpendicularly to the electrode and catheter axes. The transient simulation predicts the evolution of the temperature distribution in the tissue as well as the blood. The results can be used to optimize the design of the electrode shape in order to avoid undesirable hot spots. The simulations are also a cost-effective way of improving the quality of the therapy by studying the effect of different parameters such as blood flow rates, ablation cycle duration and electrode positioning.