Geometry and temperature distribution during radiofrequency tissue ablation: An experimental ex vivo model

Purpose: To investigate the temperature distribution and geometry of lesions created by radiofrequency (RF) tissue ablation. Materials and Methods: We developed an ex-vivo thermal model based on the ability of egg whites to coagulate at 62° to 65°C. This property allows us to observe and record the formation of "lesions" created by different commercially available RF generators and probes. Results: The lesions created by the Radionics Cool-Tip™ RF system were mostly cylindrical or barrel-shaped, while RITA® StarBurst XL™ and StarBurst XLi™ electrodes produced cone-like or mushroom-shaped lesions. The time required to achieve maximum lesion size was between 3 and 5 minutes in most trials. The formation of lesions stopped when thermodynamic equilibrium was achieved. Conclusions: The geometry of lesions does not correlate precisely with manufacturer reports, which describe spherical lesions for both RF systems. The 12-minute treatment cycle recommended by company's algorithm may not be necessary because lesion formation was completed and thermodynamic equilibrium was reached significantly earlier. We believe the results of our study may be useful in better understanding the RF ablation process, better planning, and improvement of clinical outcome.