Chen S S, Humphrey J D
Department of Mechanical Engineering, University of Maryland, Baltimore 21250, USA.
J Biomech. 1998 Mar;31(3):211-6. doi: 10.1016/s0021-9290(97)00121-8.
The outcome of many clinical heat therapies depends on the post-treatment structural integrity of the tissue. Unfortunately, there are few data on heat-induced changes in the mechanical properties of tissues due to temperature levels commonly achieved in laser, microwave, and radio-frequency-based modalities. Without such information, one cannot design optimal clinical protocols. Hence, we present new findings on the uniaxial stress strain behavior at 37 degrees C of a model collagenous tissue (chordae tendineae) both before and after thermal damage. This damage was induced via a variety of different thermo-mechanical loads: isothermal heatings at temperatures from 65 degrees C to 90 degrees C, durations of heating from 120 to 3600 s, and isotonic loads during heating from 0 to 0.65 MPa. Our data reveal that chordae exhibit pseudoelastic responses both before and after heating, but the extensibility, hysteresis, and compliance all increase with increased thermal damage. Fortunately, these complex heat-induced changes in behavior can be parameterized using a single measure of the prior thermal damage. This will clearly simplify the requisite constitutive formulations.
许多临床热疗法的效果取决于治疗后组织的结构完整性。遗憾的是，关于激光、微波和射频治疗方式中常见温度水平导致的组织力学性能热诱导变化的数据很少。没有这些信息，就无法设计出最佳的临床方案。因此，我们展示了关于模型胶原组织（腱索）在37摄氏度下热损伤前后单轴应力应变行为的新发现。这种损伤是通过多种不同的热机械负荷诱导的：温度从65摄氏度到90摄氏度的等温加热、加热持续时间从120秒到3600秒，以及加热过程中等张负荷从0到0.65兆帕。我们的数据表明，腱索在加热前后均表现出伪弹性反应，但随着热损伤增加，伸长性、滞后性和顺应性均增加。幸运的是，这些复杂的热诱导行为变化可以使用先前热损伤的单一测量指标进行参数化。这将明显简化所需的本构公式。
