Electrosurgical Vessel Sealing Tissue Temperature: Experimental Measurement and Finite Element Modeling

Abstract

The temporal and spatial tissue temperature profile in electrosurgical vessel sealing was experimentally measured and modeled using finite element modeling (FEM). Vessel sealing procedures are often performed near the neurovascular bundle and may cause collateral neural thermal damage. Therefore, the heat generated during electrosurgical vessel sealing is of concern among surgeons. Tissue temperature in an in vivo porcine femoral artery sealed using a bipolar electrosurgical device was studied. Three FEM techniques were incorporated to model the tissue evaporation, water loss, and fusion by manipulating the specific heat, electrical conductivity, and electrical contact resistance, respectively. These three techniques enable the FEM to accurately predict the vessel sealing tissue temperature profile. The averaged discrepancy between the experimentally measured temperature and the FEM predicted temperature at three thermistor locations is less than 7%. The maximum error is 23.9%. Effects of the three FEM techniques are also quantified.

Energy Dissipation in <italic>Ex Vivo</italic> Porcine Liver During Electrosurgery

“…However, computational results deviate significantly from experimental data. One of the main challenges for accurate simulation and temperature prediction lies with the accurate modeling of energy dissipation and storage processes that can be affected by temperature, frequency, and water content [3][4][5]. Another important challenge is the lack of accurate knowledge of tissue thermal properties including specific heat and thermal conductivity for a wide temperature range encountered in electrosurgery.…”

“…Surprisingly, this energy dissipation mechanism, which should play a dominant role in electrosurgery, where temperatures exceed 100 °C [12][13], is often neglected in literature and only a few studies recognize its importance in electrosurgery or similar energy based surgical methods [3][12][15]. For instance, Yang et al measured the water content of liver tissue after an ablation process by cutting liver into 5mm × 5mm × 1 mm sections and weighing them before and after vacuum drying.…”

“…The model was shown to better predict the experimental temperature data when boiling temperature of water was approached [15]. Chen et al used Yang’s effective specific heat in modeling vessel sealing in bipolar electrosurgery at high temperatures [3]. The authors note that an assumed numerical model for water loss affecting the apparent specific heat had to be made at temperatures exceeding 103 °C as no experimental data was found in literature.…”

“…While other energy dissipation mechanisms including coagulation and thermal decomposition are also expected to play a role, water makes up more than 70% of soft tissue content by mass [6] and has a very high latent heat of vaporization [3]. Thus, its evaporation from the tissue should play a dominant role in energy dissipation at elevated temperatures.…”

A mathematical model of bipolar radiofrequency-induced thermofusion

“…Dodde et al [2] developed a thermo-electric model to study the temperature distribution assuming different electrode geometries. This model was extended by Chen et al [3] to account for changes in the specific heat capacity, electrical resistance and water contents of the tissue during the thermofusion process. Gonzalez-Suarez et al [4] presented a FE model for a bipolar instrument with internally cooled electrodes.…”