University of Strasbourg, IMFS-CNRS, 2 rue Boussingault, 67000 Strasbourg, France.
J Mech Behav Biomed Mater. 2011 Nov;4(8):1905-19. doi: 10.1016/j.jmbbm.2011.06.007. Epub 2011 Jun 23.
In the case of head trauma, elongation of axons is thought to result in brain damage and to lead to Diffuse Axonal Injuries (DAI). Mechanical parameters have been previously proposed as DAI metric. Typically, brain injury parameters are expressed in terms of pressure, shearing stresses or invariants of the strain tensor. Addressing axonal deformation within the brain during head impact can improve our understanding of DAI mechanisms. A new technique based on directional measurements of water diffusion in soft tissue using Magnetic Resonance Imaging (MRI), called Diffusion Tensor Imaging (DTI), provides information on axonal orientation within the brain. The present study aims at coupling axonal orientation from a 12-patient-based DTI 3D picture, called "DTI atlas", with the Strasbourg University Finite Element Head Model (SUFEHM). This information is then integrated in head trauma simulation by computing axonal elongation for each finite element of the brain model in a post-processing of classical simulation results. Axonal elongation was selected as computation endpoint for its strong potential as a parameter for DAI prediction and location. After detailing the coupling technique between DTI atlas and the head FE model, two head trauma cases presenting different DAI injury levels are reconstructed and analyzed with the developed methodology as an illustration of axonal elongation computation. Results show that anisotropic brain structures can be realistically implemented into an existing finite element model of the brain. The feasibility of integrating axon fiber direction information within a dedicated post-processor is also established in the context of the computation of axonal elongation. The accuracy obtained when estimating level and location of the computed axonal elongation indicates that coupling classical isotropic finite element simulation with axonal structural anisotropy is an efficient strategy. Using this method, tensile elongation of the axons can be directly invoked as a mechanism for Diffuse Axonal Injury.
在头部创伤的情况下，轴突的伸长被认为会导致脑损伤，并导致弥漫性轴索损伤（DAI）。机械参数以前被提出作为 DAI 度量。通常，脑损伤参数以压力、剪切应力或应变张量不变量的形式表示。在头部冲击时解决脑内轴突变形可以提高我们对 DAI 机制的理解。一种基于磁共振成像（MRI）中软组织结构中水分子扩散的方向测量的新技术，称为弥散张量成像（DTI），提供了脑内轴突方向的信息。本研究旨在将 12 名患者的 DTI 三维图像（称为“DTI 图谱”）中的轴突方向与斯特拉斯堡大学有限元头部模型（SUFEHM）相结合。然后，通过在经典模拟结果的后处理中计算脑模型每个有限元的轴突伸长，将该信息集成到头部创伤模拟中。选择轴突伸长作为计算终点，因为它作为 DAI 预测和定位的参数具有很强的潜力。在详细描述 DTI 图谱和头部 FE 模型之间的耦合技术之后，重建并分析了两个具有不同 DAI 损伤水平的头部创伤病例，以说明轴突伸长的计算。结果表明，各向异性的脑结构可以真实地实现到现有的脑有限元模型中。在计算轴突伸长的情况下，还确定了在专用后处理器中集成轴突纤维方向信息的可行性。在估计计算得到的轴突伸长的水平和位置时获得的准确性表明，将经典各向同性有限元模拟与轴突结构各向异性相结合是一种有效的策略。使用这种方法，可以将轴突的拉伸伸长直接作为弥漫性轴索损伤的机制。
