Guzman Roberto A Pineda, Lockard Carly A, Zhou Xingyu, Bombard Evelyn, Coolbaugh Crystal, Kersh Mariana E, Damon Bruce M, Hooijmans Melissa T
Carle Clinical Imaging Research Program, Stephens Family Clinical Research Institute, Carle Health, Urbana, IL, USA.
Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
bioRxiv. 2025 Jul 29:2025.07.23.666431. doi: 10.1101/2025.07.23.666431.
Skeletal muscle generates forces that drive the motion of the human body. Three-dimensional (3D) quantification of whole-muscle architecture and strain, and their relationship during contraction is critical to understanding the mechanical function of skeletal muscle in health and disease. This has proven to be challenging, as brightness mode ultrasound is capable of measuring muscle architecture during contraction but cannot capture 3D changes in whole-muscle architecture, while Diffusion Tensor Imaging (DTI)-based tractography can measure 3D whole-muscle architecture but its use during contraction is precluded by long scan times (>5 minutes). In this study, we implement DTI-based tractography with an image registration-based approach, previously validated under passive deformation, to estimate 3D whole-muscle architecture of the tibialis anterior (TA) muscle during moderate intensity contractions (20-40% MVC). Moreover, this approach allows the measurement of whole-muscle strain during contraction, facilitating the evaluation of intramuscular relationships between architecture and strain. Our results show a decrease in the fiber-tract length, an increase in the pennation angle, and an increase in the fiber curvature of the TA during contraction. Intramuscular strain heterogeneity was observed between and within different regions of the muscle, with exploratory analyses suggesting that regional strain heterogeneity could be influenced by muscle architecture. Our results showcase the potential of MRI-based methods to obtain 3D estimates of whole-muscle architecture and strain during contraction, providing a breadth of new data that allows for new avenues of skeletal muscle biomechanical research.
骨骼肌产生驱动人体运动的力量。对全肌肉结构和应变进行三维（3D）量化，以及它们在收缩过程中的关系，对于理解骨骼肌在健康和疾病中的机械功能至关重要。事实证明，这具有挑战性，因为亮度模式超声能够在收缩过程中测量肌肉结构，但无法捕捉全肌肉结构的三维变化，而基于扩散张量成像（DTI）的纤维束成像可以测量三维全肌肉结构，但其在收缩过程中的使用因扫描时间长（>5分钟）而受到限制。在本研究中，我们采用基于图像配准的方法实施基于DTI的纤维束成像，该方法先前已在被动变形条件下得到验证，以估计中度强度收缩（20-40%最大随意收缩）期间胫骨前肌（TA）的三维全肌肉结构。此外，这种方法允许在收缩过程中测量全肌肉应变，便于评估结构与应变之间的肌内关系。我们的结果显示，收缩期间TA的纤维束长度缩短、羽状角增加以及纤维曲率增加。在肌肉的不同区域之间和区域内部均观察到肌内应变异质性，探索性分析表明区域应变异质性可能受肌肉结构影响。我们的结果展示了基于MRI的方法在获得收缩期间全肌肉结构和应变的三维估计方面的潜力，提供了大量新数据，为骨骼肌生物力学研究开辟了新途径。
