Radio-frequency electrosurgical procedures are widely used to simultaneously dissect and coagulate tissue. Experiments suggest that evaporation of cellular and intra-cellular water plays a significant role in the evolution of the temperature field at the tissue level, which is not adequately captured in a single scale energy balance equation. Here, we propose a two-scale model to study the effects of microscale phase change and heat dissipation in response to radiofrequency heating on the tissue level in electrosurgical ablation procedures. At the microscale, the conservation of mass along with thermodynamic and mechanical equilibrium is applied to obtain an equation-of-state relating vapor mass fraction to temperature and pressure. The evaporation losses are incorporated in the macro-level energy conservation and results are validated with mean experimental temperature distributions measured from electrosurgical ablation testing on ex vivo porcine liver at different power settings of the electrosurgical instrument. Model prediction of water loss and its effect on the temperature along with the effect of the mechanical properties on results are evaluated and discussed.

中文翻译：

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射频电外科组织消融的两尺度模型

射频电外科手术广泛用于同时解剖和凝固组织。实验表明，细胞和细胞内水的蒸发在组织水平的温度场演变中起着重要作用，这在单尺度能量平衡方程中并没有得到充分体现。在这里，我们提出了一个两尺度模型来研究在电外科消融过程中响应射频加热对组织水平的微尺度相变和散热的影响。在微观尺度上，应用质量守恒以及热力学和机械平衡来获得将蒸汽质量分数与温度和压力相关联的状态方程。蒸发损失被纳入宏观能量守恒，结果通过在电外科仪器的不同功率设置下对离体猪肝脏进行电外科消融测试测量的平均实验温度分布进行验证。评估和讨论了失水模型预测及其对温度的影响以及力学性能对结果的影响。