Mechanical characterization of human brain tissue
Mechanical characterization of human brain tissue
复制标题
DOI：
10.1016/j.actbio.2016.10.036
复制
发表时间：
2017-01-15
影响因子：
9.7
通讯作者：
Holzapfel, G. A.
中科院分区：
文献类型：
--
作者：
Budday, S.;Sommer, G.;Holzapfel, G. A.
力学在调节大脑形态和功能方面的作用越来越被人们所认识。计算模拟是预测健康和疾病中人类大脑机械行为的有力工具。这些模拟的成功关键取决于基本的本构模型和可靠的识别其材料参数。因此，迫切需要彻底表征脑组织的力学行为，并确定数学模型，捕捉任意负载条件下的组织响应。然而，大多数本构模型仅针对单一加载模式进行了校准。在这里，我们执行一个序列的多个加载模式在同一人脑标本-简单剪切在两个正交方向，压缩，和拉伸-和特征的加载模式特定的区域和方向的行为。我们补充这三个单独的测试相结合的多轴压缩/拉剪试验，并讨论了空调和滞后的影响。为了探索宏观结构反应在多大程度上是潜在的微观结构的结果，我们补充我们的生物力学测试与扩散张量成像和组织学。我们发现，异质的微观结构导致区域，但不是方向依赖的力学性能。我们的实验证实，人脑组织是非线性和粘弹性的，具有明显的压缩-拉伸不对称性。使用我们的测量，我们比较了五种常见的本构模型，neo-Hookean，Mooney-Rivlin，Demiray，Gent和Ogden的性能，并表明只有各向同性修改的一项Ogden模型能够代表剪切，压缩和拉伸载荷组合下的超弹性行为：具有0.4- 1.4kPa的剪切模量和负的非线性参数，其捕获压缩-拉伸不对称性和在叠加压缩而不是拉伸下的剪切应力的增加。我们的研究结果表明，材料参数确定为一个单一的加载模式无法预测在任意加载条件下的响应。我们对人脑组织的系统表征将导致更准确的计算模拟，这将使我们能够确定损伤的标准，开发智能保护系统，并预测大脑发育和疾病进展。重要性声明迫切需要表征人脑组织在多种载荷条件下的力学行为，并识别能够在这些条件下捕获组织响应的本构模型。我们在同一个大脑标本上进行了一系列的实验测试，以表征区域和方向行为，我们用DTI和组织学来补充我们的测试，以探索宏观结构反应在多大程度上是底层微观结构的结果。结果表明，人脑组织是非线性和粘弹性的，具有明显的压缩-拉伸不对称性，我们表明，多轴数据可以最好地捕获的一个长期奥格登模型的修改版本。(C)2016 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Mechanics are increasingly recognized to play an important role in modulating brain form and function. Computational simulations are a powerful tool to predict the mechanical behavior of the human brain in health and disease. The success of these simulations depends critically on the underlying constitutive model and on the reliable identification of its material parameters. Thus, there is an urgent need to thoroughly characterize the mechanical behavior of brain tissue and to identify mathematical models that capture the tissue response under arbitrary loading conditions. However, most constitutive models have only been calibrated for a single loading mode. Here, we perform a sequence of multiple loading modes on the same human brain specimen - simple shear in two orthogonal directions, compression, and tension - and characterize the loading-mode specific regional and directional behavior. We complement these three individual tests by combined multiaxial compression/tension-shear tests and discuss effects of conditioning and hysteresis. To explore to which extent the macrostructural response is a result of the underlying microstructural architecture, we supplement our biomechanical tests with diffusion tensor imaging and histology. We show that the heterogeneous microstructure leads to a regional but not directional dependence of the mechanical properties. Our experiments confirm that human brain tissue is nonlinear and viscoelastic, with a pronounced compression-tension asymmetry. Using our measurements, we compare the performance of five common constitutive models, neo-Hookean, Mooney-Rivlin, Demiray, Gent, and Ogden, and show that only the isotropic modified one-term Ogden model is capable of representing the hyperelastic behavior under combined shear, compression, and tension loadings: with a shear modulus of 0.4-1.4 kPa and a negative nonlinearity parameter it captures the compression-tension asymmetry and the increase in shear stress under superimposed compression but not tension. Our results demonstrate that material parameters identified for a single loading mode fail to predict the response under arbitrary loading conditions. Our systematic characterization of human brain tissue will lead to more accurate computational simulations, which will allow us to determine criteria for injury, to develop smart protection systems, and to predict brain development and disease progression.Statement of SignificanceThere is a pressing need to characterize the mechanical behavior of human brain tissue under multiple loading conditions, and to identify constitutive models that are able to capture the tissue response under these conditions. We perform a sequence of experimental tests on the same brain specimen to characterize the regional and directional behavior, and we supplement our tests with DTI and histology to explore to which extent the macrostructural response is a result of the underlying microstructure. Results demonstrate that human brain tissue is nonlinear and viscoelastic, with a pronounced compression-tension asymmetry, and we show that the multiaxial data can best be captured by a modified version of the one-term Ogden model. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.