CAREER: Modeling the Intervertebral Disc Using Quantitative MR Imaging

在人的一生中，脊椎骨之间的软椎间盘经常因机械原因而失效，造成巨大的疼痛。 纤维复合材料是如何失效的，对于这种类型的工程材料，当然，对于人类脊柱中更复杂的材料，都不清楚。 这个教师早期职业发展计划（CAREER）项目将有助于我们了解这些复杂材料复合材料的力学行为。 纤维增强复合材料由于纤维和来自较软的原纤外基质的大变形而提供具有更大刚度的材料。纤维复合材料在商业和军事应用中非常重要，而且对于了解人体的机械性能也很重要。许多身体组织是纤维状复合物。了解材料在其工作环境下的力学行为以及载荷如何在相邻组织之间传递是理解多种疾病的重大挑战。 特别是，人类脊柱的“椎间盘突出”是我们不了解的纤维复合结构的失败。传统的材料测试技术需要将试样从其工作位置移除，从而显著改变加载环境和边界条件。高分辨率磁共振成像提供了一种非侵入性的方法来确定在一个活生生的人没有受伤的椎间盘的组成。 该项目将支持关于生物组织如何因组成变化而改变其机械特性的基础研究。这项工作将基于磁共振成像方法，因为以后，该项目的结果可以作为一种非侵入性，安全的方式用于评估人体组织机械行为的变化。该项目将有助于推动椎间盘力学领域的发展，研究成果应适用于身体的其他软组织。对社区的宣传包括一项计划，以加强STEM参与女孩的基础上，主要研究者在当地奥克兰，加利福尼亚州和伯克利，加利福尼亚州K-12学校的持续努力。参与的本科生和研究生的外展activities.Noninvasive磁共振成像与有限元建模相结合，解决了许多限制与当前的方法来了解复合结构的力学行为，如椎间盘的影响。该盘包括由纤维增强材料包围的软凝胶状材料。水化和肿胀对于椎间盘的机械功能是重要的，并且已知退化的变化会改变椎间盘的组成和力学。组织成分的变化导致残余应力、组织各向异性和失效力学的改变。圆盘为理解两种不同材料之间应力分布的变化提供了一个很好的模型。研究小组将使用定量磁共振成像直接测量水和蛋白聚糖成分的特殊变化，这将用于开发一个特定于受试者的计算模型，该模型将通过关节和组织水平的实验进行验证。所获得的知识将是重要的1）理解软组织力学与损伤和退化的变化，2）开发创新的工具，研究软材料力学，和3）该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响进行评估来支持的审查标准。

The soft discs between the bones in the human spine fail from mechanical causes often during life, causing a great deal of pain. How fibrous composites fail is not understood either for engineering materials of this type or, of course, for the more complex material in the human spine. This Faculty Early Career Development Program (CAREER) project will contribute to our understanding of the mechanical behavior of these complex material composites. Fiber-reinforced composites provide materials with greater stiffness due to the fibers and large deformations from the softer extrafibrillar matrix. Fiber composites are important in commercial and military applications, but also to understanding the mechanical properties of human bodies. Many body tissues are fibrillar composites. Understanding the mechanical behavior of the material under its working environment and how load is transferred between neighboring tissues is a significant challenge to understanding multiple diseases. In particular, "slipped disc" of the human spine is a failure of the fibrillar composite structure that we don't understand. Traditional material testing techniques require specimens to be removed from their working position, significantly altering the loading environment and boundary conditions. High-resolution magnetic resonance imaging provides a noninvasive approach for determining the composition of a spinal disc in a live person without injury. This project will support fundamental research on how biological tissues change their mechanical properties as a result of changes in composition. The work will be based on magnetic resonance imaging methods because, later, the results of the project can be used in living people as a noninvasive, safe way to assess changes in mechanical behavior of body tissues. The project will help to advance the field of disc mechanics, and the research results should apply to other soft tissues of the body. Outreach to the community includes a plan to enhance STEM engagement for girls based on the Principal Investigator's ongoing efforts in local Oakland, CA and Berkeley, CA K-12 schools. Involvement of undergraduate and graduate students in the outreach activities substantially amplifies the impact.Noninvasive magnetic resonance imaging in combination with finite element modeling addresses many limitations with current approaches for understanding the mechanical behavior of composite structures, such as the intervertebral disc. The disc includes a soft gel-like material surrounded by a fiber-reinforced material. Hydration and swelling are important for the mechanical function of the disc and changes with degeneration are known to alter disc composition and mechanics. Changes in tissue composition result in altered residual stresses, tissue anisotropy, and failure mechanics. The disc provides an excellent model for understanding changes in stress distribution between two distinct materials. The research team will use quantitative magnetic resonance imaging to directly measure special changes in water and proteoglycan composition, which will be used to develop a subject-specific computational model that will be validated through joint- and tissue-level experiments. The knowledge gained will be important for 1) understanding changes in soft tissue mechanics with injury and degeneration, 2) developing innovative tools for studying soft material mechanics, and 3) understanding the underlying mechanisms that govern load distributions in complex soft materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.