Center for Applied Biomechanics, University of Virginia, 4040 Lewis and Clark Dr, Charlottesville, VA, 22911, USA.
Ann Biomed Eng. 2019 Sep;47(9):1908-1922. doi: 10.1007/s10439-019-02239-8. Epub 2019 Mar 14.
Many human brain finite element (FE) models lack mesoscopic (~ 1 mm) white matter structures, which may limit their capability in predicting TBI and assessing tissue-based injury metrics such as axonal strain. This study investigated an embedded method to explicitly incorporate white matter axonal fibers into an existing 50th percentile male brain model. The white matter was decomposed into myelinated axon tracts and an isotropic ground substance that had similar material properties to gray matter. The axon tract bundles were derived from a population-based tractography template explicitly modeled using 1-D cable elements. The axonal fibers and ground substance material were implemented using hyper-viscoelastic constitutive models, which were calibrated using white and gray matter brain tissue material testing data available in the literature. Finally, the new axon-based model was extensively validated for brain-skull relative deformation under various loading conditions (n = 17) and showed good biofidelity compared to other brain models. Through these analyses, we demonstrated the applicability of this method for incorporating axonal fiber tracts into an existing FE brain model. The axon-based model will be a useful tool for understanding the mechanisms of TBI, evaluating tissue-based injury metrics, and developing injury mitigation systems.
许多人类大脑有限元（FE）模型缺乏介观（~1 毫米）白质结构，这可能限制了它们预测 TBI 和评估基于组织的损伤指标（如轴突应变）的能力。本研究探讨了一种嵌入式方法，即将白质轴突纤维明确纳入现有的 50 百分位男性大脑模型中。白质被分解为有髓鞘的轴突束和各向同性的基质，其材料特性与灰质相似。轴突束是从基于人群的束追踪模板中获得的，该模板明确使用 1-D 电缆元素进行建模。轴突纤维和基质材料使用超粘弹性本构模型实现，该模型使用文献中可用的白质和灰质脑组织材料测试数据进行校准。最后，新的基于轴突的模型在各种加载条件下（n=17）对脑-颅骨相对变形进行了广泛验证，与其他大脑模型相比具有良好的生物逼真度。通过这些分析，我们证明了将轴突纤维束纳入现有 FE 大脑模型的方法的适用性。基于轴突的模型将成为理解 TBI 机制、评估基于组织的损伤指标和开发损伤缓解系统的有用工具。
