Measuring Anisotropy in Fibrous Soft Materials by MR Imaging of Slow and Fast Shear Waves

本研究的目的是测量纤维软材料的方向依赖性，机械性能，如人造组织，肌肉或大脑中的白色物质。所提出的方法是使用磁共振成像来可视化和测量弹性波在材料中的传播。波通过固体材料的传播速度取决于其刚度，而在纤维材料中，刚度取决于加载方向。通过使用磁共振成像来可视化剪切波，可以在没有侵入性程序或破坏性测试的情况下估计这些机械性能。这种方法将通过将其应用于测量纤维蛋白凝胶的机械性能来验证，其中纤维排列是通过在磁场中聚合凝胶来产生的。然后，它将被用于非侵入性地表征大脑的机械特性。如果成功，该研究的好处将包括提高建模和模拟纤维材料行为的能力。它将使准确的计算机模拟创伤性脑损伤的机制，并提高对损伤力学的理解。由于大脑中的白色物质对机械变形特别敏感，因此对其进行正确建模的能力对于保护装置的设计和治疗方法的开发极其重要。此外，拟议的研究可能会导致新的方法来监测肌肉，肌腱，大脑或人造组织的状况。 该项目中使用的工程凝胶也可能具有医学应用，作为神经生长的组织替代物或支架。该项目的一个广泛的好处是，高中和本科工程专业的学生将学习应用最先进的成像方法来理解一类重要材料的复杂力学行为。

The objectives of this research are to measure the direction-dependent, mechanical properties of fibrous soft materials, such as artificial tissue, muscle or white matter in the brain. The proposed approach is to use magnetic resonance imaging to visualize and measure the propagation of elastic waves in the material. The speed of wave propagation through a solid material depends on its stiffness, and in a fibrous material the stiffness depends on the direction of loading. By using magnetic resonance imaging to visualize shear waves, it is possible to estimate these mechanical properties without invasive procedures or destructive testing. This approach will be validated by applying it to measure mechanical properties of fibrin gels in which fiber alignment is produced by polymerizing the gel in a magnetic field. It will then be used to non-invasively characterize mechanical properties of the brain.If successful, the benefits of the research will include an improved ability to model and simulate the behavior of fibrous materials. It will enable accurate computer simulations of the mechanisms of traumatic brain injury and improved understanding of injury mechanics. Since white matter in the brain is particularly sensitive to mechanical deformation, the ability to model it correctly is extremely important to the design of protective devices and the development of therapeutic approaches. In addition, the proposed research may lead to new methods to monitor the condition of muscle, tendon, brain, or artificial tissue. The engineered gels used in this project may also have medical applications as tissue surrogates or scaffolds for nerve growth. A broad benefit of the project is that high school and undergraduate engineering students will learn to apply state-of-the-art imaging methods to understand complex mechanical behavior of an important class of materials.