NeuroPoly Lab, Polytechique Montreal, Montreal, Quebec, Canada; Montreal Heart Institute, University of Montreal, Montreal, Quebec, Canada; Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey.
Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey.
J Mech Behav Biomed Mater. 2023 Mar;139:105681. doi: 10.1016/j.jmbbm.2023.105681. Epub 2023 Jan 17.
Coupled with diffusion tractography, non-rigid registration of high-resolution anatomical MR images allows the calculation of local strains along human skeletal muscle fascicles in-vivo. A reference study (passively imposed lengthening of gastrocnemius medial muscle) reported local shortening and lengthening occurring along the same muscle fascicles. However, the robustness of strain amplitudes and distribution patterns should be studied, as the heterogeneity of local length changes has major implications for muscle function. Using a previous image set of human medial gastrocnemius (GM) we aimed at testing: (1) the consistency of our MRI-DTI analysis workflow against changes made to the software environments, (2) the hypothesis that non-rigid demons algorithm tuning parameters (16 paired combinations were tested) are not a significant determinant of muscle fiber direction strain heterogeneity caused by passive knee extension. A profoundly altered analysis workflow did reproduce the original results well, showing a general pattern of proximally lengthened and distally shortened muscle fascicles (strain amplitude range: 21%-67%). Hierarchical shift function analyses and pairwise comparison of strain distributions between 10 equal parts of the tracked GM fascicles confirmed the hypothesis showing no significant effects of tuning parameters determining the in-vivo deformation field inhomogeneity. The findings show the robustness of the MRI-DTI method, and confirming the hypothesis, also the consistency of along muscle fascicle strain heterogeneity patterns against parameter selection. However, the strain amplitudes do vary with parameter choices. New studies are indicated to determine optimal tuning parameters to achieve accurate strain amplitudes compared to exact strains.
结合弥散张量成像（diffusion tractography），高分辨率解剖磁共振图像的非刚性配准允许计算人体骨骼肌纤维束的局部应变。一项参考研究（被动拉长比目鱼肌内侧肌肉）报告了在同一肌肉纤维束中发生的局部缩短和伸长。然而，应变幅度和分布模式的稳健性应该进行研究，因为局部长度变化的异质性对肌肉功能有重大影响。利用先前的一组人类比目鱼肌内侧（GM）图像，我们旨在测试：（1）我们的 MRI-DTI 分析工作流程对软件环境变化的一致性，（2）非刚性 demons 算法调整参数（测试了 16 对组合）不是被动膝关节伸展引起的肌纤维方向应变异质性的重要决定因素的假设。一个经过深刻改变的分析工作流程很好地再现了原始结果，显示了一个普遍的近端延长和远端缩短的肌肉纤维束模式（应变幅度范围：21%-67%）。分层移位函数分析和对跟踪 GM 纤维束的 10 个相等部分之间的应变分布进行的成对比较证实了这一假设，即调整参数没有显著影响确定体内变形场非均匀性的参数。研究结果表明 MRI-DTI 方法的稳健性，并证实了假设，即沿肌肉纤维束应变异质性模式的一致性也不受参数选择的影响。然而，应变幅度确实随参数选择而变化。需要进行新的研究来确定最佳的调整参数，以实现与精确应变相比的准确应变幅度。
