Abstract
BackgroundBipolar vessel sealing is an efficient electrosurgical procedure for the occlusion of blood vessels particularly during minimally invasive surgery. Reliable knowledge of the thermal spread is crucial for a safe application of bipolar vessel sealing instruments when operating close to thermo-sensitive structures, such as nerves. The evolution of the thermal spread over time and space depends on a variety of parameters, such as the biological tissue, the energy applied to the tissue, and the geometry of the vessel sealing instrument. Mathematical modeling has proven useful for the prediction of the thermal spread. It is, thus, a promising tool for the systematic analysis of the influence of geometrical changes on the thermal spread.ResultsWe present an experimentally validated in silico study to evaluate the impact of geometry variations on the progression of chicken egg white coagulation and the final shape of coagulated egg white as an approximation of the temporal and spatial evolution of the thermal spread during bipolar vessel sealing. Egg white has similar thermal and electrical properties to human tissue, with the advantage being that the spatial and temporal evolution of the thermal spread can be visually gauged. The simulations were performed using a mathematical model based on the finite element analysis of chicken egg white. The progression of egg white coagulation was predicted for two different peak voltages and various electrode geometries. Starting with two planar electrodes, one electrode was gradually changed to adopt a wedge shape. These changes to the geometry showed a distinct influence on the progression of egg white coagulation in the simulations. The predictions were successfully validated using an experimental setup with two different electrodes representing the extreme geometries.DiscussionThe predicted spatial temperature distributions were experimentally validated for two geometries. Our simulation study shows that the geometry has a pronounced influence on the thermal spread and, thus, is a suitable parameter to reduce thermal damage. The in silico optimization of instrument designs is a suitable tool to accelerate the development of new vessel sealing instruments, with only a few promising designs having to be tested as prototypes.
Highlights
Bipolar vessel sealing is an efficient electrosurgical procedure for the occlusion of blood vessels during minimally invasive surgery
Mathematical model The radiofrequency-induced electrical heating of chicken egg white can be mathematically described by the partial differential equation (PDE) system
Simulation study We conducted an in silico study to investigate how the geometry of the electrodes influence the progression of egg white coagulation and the shape of the coagulated egg white, and the thermal spread using our previously published model [19]
Summary
Bipolar vessel sealing is an efficient electrosurgical procedure for the occlusion of blood vessels during minimally invasive surgery. A major advantage of bipolar vessel sealing is the nearly bloodless preparation of tissue structures in a short time without foreign matter remaining in the body This significantly reduces surgical time and postoperative wound bleeding compared to conventional ligation [5, 6]. One challenge is the thermal damage of the lateral tissue, especially when operating in the proximity to thermosensitive structures, such as other nearby vessels [7] or, more importantly, nerves, where temperatures of only 43 °C could irreversibly impair the neural tissue [8] This usually leads to a significantly reduced quality of life, for example, when thermal damage of the nearby neurovascular bundle during radical prostatectomy impairs urinary continence and erectile function [9]
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