Investigation of Thermal Spread during Electrosurgical Coagulation in Neurosurgery.

Abstract

This study investigates the thermal spread during electrosurgical coagulation and develops a tissue-mimicking phantom material for electrosurgical simulator. Bipolar coagulation is an important procedure to control bleeding in neurosurgery. However, the thermal damage caused by electrosurgical coagulation can lead to postoperative issues and is detrimental to a patient's long-term recovery. This study aims to quantify the thermal spread during coagulation experimentally and numerically, and to develop a phantom material as a training tool that allows the education of surgeons for the use of electrosurgical devices. Thermal profiles of coagulation on porcine spinal cord using bipolar forceps, including stainless steel, titanium, heat-pipe embedded, and SILVERGlide forceps, are experimentally measured. The heating and cooling effects of each forceps are compared. The heat-pipe embedded and SILVERGlideTM forceps have less heating effect and allow for a precision coagulation. Heat-pipe embedded forceps also show the best cooling efficiency at high temperature. A comprehensive numerical model, with multi-physics, thermal and electrical fields, and two phases, liquid and solid, is developed to predict tissue spatial and temporal temperature, as well as the thermal dose during coagulation. It is important to incorporate the fluid phase, because when the coagulation is performed with the existence of cerebrospinal fluid, the fluid layer is subject to the electrical field and has an electrothermally induced flow which changes the temperature distribution. Modeling techniques to account for the water evaporation, change of material properties due to water loss, and tissue fusion during the coagulation process are also developed. The averaged error of the temperature predicted by the model is 4.2 %. A systematic approach is developed to formulate gellan gum-based tissue-mimicking phantom with targeted elastic modulus, thermal conductivity, and electrical conductivity. A spinal cord-like phantom is made based on this approach and has close (<3% error) properties to spinal cord tissue. This phantom is validated to be able to reproduce the temperature response as spinal cord tissue and can be used to build a clinical simulator for electrosurgery.