Analysis of thermoviscoelastic behavior in cartilage

描述(申请人提供)：在激光软骨重塑(LCR)中，形状改变是通过首先机械变形组织，然后使用激光将其快速加热到大约60-70℃来完成的。使用LCR，头部和颈部的软骨可以被重塑成新的稳定的几何形状，而不需要切割或缝合来缓解和/或平衡抵抗变形的内力。该建议的具体目标包括：1)确定激光辐照软骨移植物的急性和长期机械稳定性，2)表征软骨中产生热的机械应力行为之间的关键关系，3)建立有限元模型来模拟软骨的热粘弹性以进行参数分析，以及4)将形状变化与存活率和激光剂量学相关联。这些目标是对S现有的K-08 MCSDA中概述的目标的补充和扩展。将使用细胞/组织培养技术和活体兔模型来评估软骨对激光照射的急性和长期反应。热分析(如材料科学中使用的)将被用来表征软骨的温度依赖的热和力学性能，并且这些结果将被合并到有限元耦合热传递和粘弹性行为中。将对关键变量和过程的应力/应变场和温度分布进行参数分析，并在激光重塑样本中测量组织存活的同时用于优化LCR。将确定在保持组织活力的同时产生有效形状变化的激光参数的范围，并将使用有限元计算相变能量需求的估计。由于软骨的形状变化对应于应力松弛，了解加速这一过程所需的能量(相变能量)将是优化的关键因素，因为这种能量沉积在很大程度上取决于剂量学和组织的热和光学性质。这项建议将致力于发展对形状变化过程的更有说服力的理解，并促进LCR从实验室安全地转移到美国的临床。由于热组织重塑和修改是一个日益增长的研究课题，本建议侧重于建立在活组织中控制这些过程的长期机械行为和基本物理机制。

DESCRIPTION (provided by applicant): In Laser Cartilage Reshaping (LCR), shape change is accomplished by first mechanically deforming the tissue and then heating it rapidly using a laser to approximately 60-70 degrees C. Using LCR, cartilages in the head and neck may be reshaped into new stable geometries without the need for cutting or suturing to relieve and/or balance the intrinsic forces that resist deformation. The specific objectives of this proposal include: 1) determining both the acute and long-term mechanical stability of laser irradiated cartilage grafts, 2) characterizing the critical relationship between mechanical stress behavior in response to heat generation in cartilage, 3) developing a finite element model (FEM) to simulate thermoviscoelasticity in cartilage in order to perform parametric analysis, and 4) correlating shape change with viability and laser dosimetry. These aims complement and extend the objectives outlined in the P.l.'s existing K-08 MCSDA. Cell/tissue culture techniques and an in vivo rabbit model will be used to evaluate the acute and long-term response of cartilage to laser irradiation. Thermal analysis (as used in materials science) will be performed to characterize cartilage temperature dependent thermal and mechanical properties, and these results will be incorporated into the FEM coupling heat transfer and viscoelastic behavior. Parametric analysis of the stress/strain field and temperature distribution to key variables and processes will be performed and used to optimize LCR in parallel with measurements of tissue viability in laser reshaped specimens. The range of laser parameters that produce effective shape change while preserving tissue viability will be determined, and estimates of phase transformation energy requirements will be calculated using the FEM. Since shape change in cartilage corresponds to stress relaxation, knowing the energy required to accelerate this process (phase transformation energy) will be a key factor in optimization since this energy deposition is largely determine by dosimetry and tissue thermal and optical properties. This proposal will focus on developing a more cogent understanding of the shape change process, and facilitate the safe transfer of LCR from the laboratory to the clinic in the U.S. Inasmuch as thermal tissue reshaping and modification is a growing topic of research, this proposal focuses on establishing the long-term mechanical behavior and fundamental physical mechanisms governing these processes in living tissues.