Electrosurgical tissue resection: a numerical study

The nature of the electrical, thermal mechanical and chemical phenomena associated with an electrosurgical resection of biological tissues is an important aspect of general surgery and other specialized medical treatments. A better understanding of the phenomena and the ability to model them are indispensable if advancements in the state of the art are to be achieved. This study particularly emphasizes two of the phenomena that have significant influence on the outcome of the electrosurgical procedure. These are the nature of the electric contact between tissue and electrosurgical scalpel and the mechanism of tissue water vaporization and subsequent mechanical damage to the tissue due to interstitial formation of the vapor micro bubbles and vacuoles. A numerical model of the interaction between tissue and electrosurgical scalpel was used to study the vaporization process at a number of power settings and for different scalpel geometries. An electric discharge striking between tissue and electrode was investigated and incorporated into an analytical model used for numerical simulation. For the water vaporization effect, surface evaporation at the tissue scalpel contact area and bulk vapor nucleation are introduced to facilitate the modeling of the change in tissue thermal and electric properties and tissue mechanical and thermal damage. A number of physical experiments were performed on beef muscle and saline and water samples to establish experimental values for the numerical model and observe electric circuit parameters, temperature variations and thermal damage cause by the electrosurgical current. These results are compared to those obtained from the simulations performed for the tissue-scalpel electric contact achieved by means of electric sparks, pure mechanical and mixed spark-mechanical contact. The simulation results for the contact through sparks alone are in least agreement and for the pure mechanical contact are in reasonably good agreement with those observed experimentally. It is reasonable to conclude that the sparks do not dominate the process of electrosurgical tissue resection though they contribute to formation of tissue thermal damage.