A multi-physics model has been developed to investigate the effects of cellular level mechanisms on the thermomechanical response of ultrasonically activated soft tissue. Cellular level cavitation effects have been incorporated in the tissue level continuum model to accurately determine the thermodynamic states such as temperature and pressure. A viscoelastic material model is assumed for the macromechanical response of the tissue. The cavitation model based equation-of-state provides the additional pressure arising from evaporation of intracellular and cellular water by absorbing heat due to structural and viscoelastic heating in the tissue, and temperature to the continuum level thermomechanical model. The thermomechanical response of soft tissue is studied for the operational range of frequencies of oscillations and applied loads for typical ultrasonically activated surgical instruments. The model is shown to capture characteristics of ultrasonically activated soft tissue deformation and temperature evolution. At the cellular level, evaporation of water below the boiling temperature under ambient conditions is indicative of protein denaturation around the temperature threshold for coagulation of tissues. Further, with increasing operating frequency (or loading), the temperature rises faster leading to rapid evaporation of tissue cavity water, which may lead to accelerated protein denaturation and coagulation.

中文翻译：

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超声波激活软组织的多物理场模型

已经开发了一个多物理模型来研究细胞水平机制对超声激活软组织的热机械响应的影响。细胞水平空化效应已被纳入组织水平连续模型，以准确确定热力学状态，如温度和压力。假设粘弹性材料模型用于组织的宏观力学响应。基于状态方程的空化模型通过吸收由于组织中的结构和粘弹性加热而产生的热量和温度到连续介质水平热机械模型，从而提供由细胞内和细胞水蒸发产生的额外压力。针对典型的超声激活手术器械的振荡频率和施加载荷的操作范围，研究了软组织的热机械响应。该模型可以捕捉超声激活的软组织变形和温度演变的特征。在细胞水平上，在环境条件下低于沸腾温度的水蒸发表明蛋白质在组织凝固的温度阈值附近发生变性。此外，随着操作频率（或负荷）的增加，温度升高更快，导致组织腔内水分快速蒸发，这可能导致蛋白质变性和凝固加速。该模型可以捕捉超声激活的软组织变形和温度演变的特征。在细胞水平上，在环境条件下低于沸腾温度的水蒸发表明蛋白质在组织凝固的温度阈值附近发生变性。此外，随着操作频率（或负荷）的增加，温度升高更快，导致组织腔内水分快速蒸发，这可能导致蛋白质变性和凝固加速。该模型可以捕捉超声激活的软组织变形和温度演变的特征。在细胞水平上，在环境条件下低于沸腾温度的水蒸发表明蛋白质在组织凝固的温度阈值附近发生变性。此外，随着操作频率（或负荷）的增加，温度升高更快，导致组织腔内水分快速蒸发，这可能导致蛋白质变性和凝固加速。