Noninvasive tools for assessing muscle structure and function

项目摘要 肌肉力量和刚度的变化是姿势和运动控制的基础。这些基本能力 在几乎所有的运动障碍中受损，包括中风，脑瘫， 肌肉骨骼损伤或疼痛。康复可以从重新建立健康的生活方式的角度来考虑。 肌肉力量和僵硬度。因此，生物力学领域的一个根本挑战， 长期以来，运动控制和身体康复一直在测量健康状况下的肌肉力量和刚度， 疾病，但没有严格的方法来做到这一点非侵入性。超声剪切波弹性成像 (SWE)被提出作为一种非侵入性的工具来测量刚度，但我们已经证明，SWE是 不仅对肌肉硬度敏感，而且对力敏感，并且这些依赖性在不同的肌肉类型中是不同的。 虽然我们的研究结果对许多先前研究的结论提出了质疑，但它们也表明， 被重新设想为一种非侵入性测量刚度和力的工具。这项建议的目的是 评估这种有趣的可能性，它可以改变人类运动的研究，并指导康复 治疗多种运动障碍的方案 我们的长期目标是改善与肌肉变化相关的肌肉骨骼疾病的治疗， 力或刚度。我们的中心假设是，肌肉的硬度和力量可以唯一地确定从 SWE通过考虑肌肉的独特结构。剪切波的传播对 肌肉应力（按横截面积标准化的力）和刚度，但尚不清楚SWE是否可以 独立地测量这些量。目标1和2将量化被动延长的应力， 主动收缩改变剪切波传播平行于肌纤维的方向，如通过 一维超声阵列目前可用于诊所。研究将在动物模型中进行 因此，SWE测量可以与肌肉刚度和应力的直接测量进行比较（目标1）， 考虑到几种人体肌肉的复杂性，这些肌肉被认为具有应力的内部变化（目标2）。 最后，我们将评估我们开发的使用多方向SWE来确定 无创性肌肉应力和刚度（目标3）;这将使用3D打印生物材料组合实现 用已知的机械性能，从我们的动物模型和人体实验中获得的肌肉， 严格测试这种创新的方法，并根据需要调整它，以解释肌肉的独特结构。 我们希望我们的目标将明确目前SWE的应用所衡量的内容， 肌肉，并确定一种采用多方向SWE的新方法是否可用于测量肌肉力量 和硬度。这种能力将对康复产生变革性影响， 评估肌肉的关键特性，使人类运动或有助于其损害。

Project Summary Changes in muscle force and stiffness underlie the control of posture and movement. These fundamental abilities are impaired in almost all movement disorders, including those resulting from stroke, cerebral palsy, musculoskeletal injury, or pain. Rehabilitation can be framed in terms of re-establishing healthy patterns of muscle force and stiffness for each patient. Consequently, a fundamental challenge in the fields of biomechanics, motor control, and physical rehabilitation has long been measuring muscle force and stiffness in health and disease, yet there are no rigorous methods for doing so noninvasively. Ultrasound shear wave elastography (SWE) was proposed as a noninvasive tool for measuring stiffness, but we have demonstrated that SWE is sensitive not only to muscle stiffness but also to force, and that these dependencies vary across muscle types. While our results call into question conclusions from many previous studies, they also suggest that SWE could be reimagined as a tool for noninvasively measuring both stiffness and force. The objective of this proposal is to evaluate this intriguing possibility, which could transform the study of human movement and guide rehabilitation protocols for numerous motor disorders. Our long-term goal is to improve treatments for musculoskeletal disorders associated with changes to muscle force or stiffness. Our central hypothesis is that muscle stiffness and force can be uniquely determined from SWE by considering the distinctive structure of muscle. Shear wave propagation is sensitive to changes in muscle stress (force normalized by cross-sectional area) and stiffness, but it remains unknown if SWE can independently measure these quantities. Aims 1 and 2 will quantify how stresses from passive lengthening and active contraction alter shear wave propagation parallel to the direction of muscle fibers, as measured by the one-dimensional ultrasound arrays currently available in clinics. Studies will be conducted in an animal model so that SWE measurements can be compared to direct measures of muscle stiffness and stress (Aim 1), before considering the complexities of several human muscles thought to have internal variations in stress (Aim 2). Finally, we will evaluate the novel technique we have developed that uses multi-directional SWE to determine muscle stress and stiffness noninvasively (Aim 3); this will occur using a combination of 3D-printed biomaterials with known mechanical properties, muscles harvested from our animal model, and human experiments to rigorously test this innovative approach and adapt it as needed to account for the unique structure of muscle. We expect that our aims will clarify precisely what is being measured by current applications of SWE to muscle and determine if a novel approach employing multidirectional SWE can be used to measure muscle force and stiffness noninvasively. Such an ability would be transformative for rehabilitation, providing quantitative assessments of the critical properties of muscle that enable human movement or contribute to its impairment.