Toward a Tissue Model for Bipolar Electrosurgery: Block-Oriented Model Structure Analysis

High-frequency radio energy is applied to tissue therapeutically in a number of different medical applications. The ability to model the effects of RF energy on the collagen, elastin, and liquid content of the target tissue would allow for the refinement of the control of the energy in order to improve outcomes and reduce negative side effects. In this paper, we aim at studying the dynamics of voltage and current signals in bipolar electrosurgery whose dynamic relationship we describe by a nonlinear (NL) time-varying dynamical model. The different aspects and carefully designed tests allow getting insight in a possible candidate for such a dynamical model. We conclude, in this paper, that the impedance relationship may be modeled through a time-varying Wiener-Hammerstein system where the static NL function is a function of both the signal as well as time. In particular, we motivate that one can discriminate between different target tissues through this model by inspecting the time-varying NL function. As such, the model properties serve the realization of a possible simulator generating real-life current-voltage signals for training facilities among other applications.