In silico evaluation of geometry variations with respect to the thermal spread during coagulation of egg white using bipolar vessel sealing instruments.
BACKGROUND
Bipolar 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.


RESULTS
We 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.


CONCLUSIONS
The 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.
Institute for System Dynamics, University of Stuttgart, Waldburgstr. 19, 70563, Stuttgart, Germany. jay.wagenpfeil@isys.uni-stuttgart.de.
Jay
http://orcid.org/0000-0002-0218-6596
J
Wagenpfeil
Institute for System Dynamics, University of Stuttgart, Waldburgstr. 19, 70563, Stuttgart, Germany.|Medical Technology Group, Technische Universität Berlin, Dovestr. 6, 10587, Berlin, Germany.
Christina
C
Schöllig
Erbe Elektromedizin GmbH, Waldhörnlestr. 17, 72072, Tübingen, Germany.
Volker
V
Mayer
Institute for System Dynamics, University of Stuttgart, Waldburgstr. 19, 70563, Stuttgart, Germany.
Ronny
R
Feuer
Erbe Elektromedizin GmbH, Waldhörnlestr. 17, 72072, Tübingen, Germany.
Bernhard
B
Nold
Erbe Elektromedizin GmbH, Waldhörnlestr. 17, 72072, Tübingen, Germany.
Alexander
A
Neugebauer
Erbe Elektromedizin GmbH, Waldhörnlestr. 17, 72072, Tübingen, Germany.
Michael
M
Ederer
University Women's Hospital, Calwerstr. 7, 72076, Tübingen, Germany.
Ralf
R
Rothmund
University Women's Hospital, Calwerstr. 7, 72076, Tübingen, Germany.
Bernhard
B
Krämer
University Women's Hospital, Calwerstr. 7, 72076, Tübingen, Germany.
Sara
S
Brucker
Erbe Elektromedizin GmbH, Waldhörnlestr. 17, 72072, Tübingen, Germany.
Markus
M
Enderle
Institute for System Dynamics, University of Stuttgart, Waldburgstr. 19, 70563, Stuttgart, Germany.
Oliver
O
Sawodny
Institute for System Dynamics, University of Stuttgart, Waldburgstr. 19, 70563, Stuttgart, Germany.
Julia
J
Rex
D000818:Animals; D032701:Biomimetics; D002645:Chickens; D003198:Computer Simulation; D004529:Egg White / Q000737:chemistry*; D011846:Radio Waves; D013696:Temperature; D014656:Vascular Surgical Procedures / Q000295:instrumentation*
Bipolar vessel sealing; Egg white model; Finite element analysis; Mathematical modeling; Thermal spread