Waveform-Dependent Electrosurgical Effects on Soft Hydrated Tissues

Abstract

Electrosurgical procedures are ubiquitously used in surgery. The commonly used power modes, including the coagulation and blend modes, utilize nonsinusoidal or modulated current waveforms. For the same power setting, the coagulation, blend, and pure cutting modes have different heating and thermal damage outcomes due to the frequency dependence of electrical conductivity of soft hydrated tissues. In this paper, we propose a multiphysics model of soft tissues to account for the effects of multifrequency electrosurgical power modes within the framework of a continuum thermomechanical model based on mixture theory. Electrical and frequency spectrum results from different power modes at low-and high-power settings are presented. Model predictions are compared with in vivo electrosurgical heating experiments on porcine liver tissue. The accuracy of the model in predicting experimentally observed temperature profiles is found to be overall greater when frequency-dependence is included. An Arrhenius type model indicates that more tissue damage is correlated with larger duty cycles in multifrequency modes.

Effects of the signal modulation on the response of human fibroblasts to in vitro stimulation with subthermal RF currents

“…We have also reported that, as is the case for other RF electric and magnetic fields, the cellular response to CRET currents is non-linearly dependent on the frequency of the sinusoidal signal (Hernández-Bule et al 2019). The modulation of the carrier signal is another parameter that has been shown relevant, both in the bioeffects induced by RF electromagnetic fields (Barbault et al 2009;Blackman 2012;Juutilainen et al 2011) as in those elicited by RF electric currents such as those used by the electric scalpel when in modes cutting vs. coagulation (Karaki et al 2019). Thus, it is conceivable that modulation of the RF signal could also significantly influence the cellular response to CRET electric stimulation.…”

Heat conduction in live tissue during radiofrequency electrosurgery

“…As we are only considering a single electrosurgery probe in this paper, we can approximate the source by a three-dimensional (3D) Gaussian distribution as Qfalse(xfalse)=Q0exp⁡false[−∑n=13xi2/false(2σ2false)false], where Q 0 is the magnitude of the source and σ is the radius of the source. Note that with this approximation, the source radius σ should be adjusted based on the power mode being selected at the electrosurgical generator because the electrical conductivity of biological tissue is waveform-dependent [36]. In the pure cut mode, the current should be concentrated extremely close to the tip of the probe; therefore we could approximate σ with the diameter of the electrosurgery tip.…”