Yoganandan Narayan, Li Jianrong, Zhang Jiangyue, Pintar Frank A, Gennarelli Thomas A
Department of Neurosurgery, Medical College of Wisconsin and VA Medical Center, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, USA.
J Biomech. 2008 Jul 19;41(10):2253-62. doi: 10.1016/j.jbiomech.2008.04.019. Epub 2008 Jun 16.
Recognizing the association of angular loading with brain injuries and inconsistency in previous studies in the application of the biphasic loads to animal, physical, and experimental models, the present study examined the role of the acceleration-deceleration pulse shapes on region-specific strains. An experimentally validated two-dimensional finite element model representing the adult male human head was used. The model simulated the skull and falx as a linear elastic material, cerebrospinal fluid as a hydrodynamic material, and cerebrum as a linear viscoelastic material. The angular loading matrix consisted coronal plane rotation about a center of rotation that was acceleration-only (4.5 ms duration, 7.8 krad/s/s peak), deceleration-only (20 ms, 1.4 krad/s/s peak), acceleration-deceleration, and deceleration-acceleration pulses. Both biphasic pulses had peaks separated by intervals ranging from 0 to 25 ms. Principal strains were determined at the corpus callosum, base of the postcentral sulcus, and cerebral cortex of the parietal lobe. The cerebrum was divided into 17 regions and peak values of average maximum principal strains were determined. In all simulations, the corpus callosum responded with the highest strains. Strains were the least under all simulations in the lower parietal lobes. In all regions peak strains were the same for both monophase pulses suggesting that the angular velocity may be a better metric than peak acceleration or deceleration. In contrast, for the biphasic pulse, peak strains were region- and pulse-shape specific. Peak values were lower in both biphasic pulses when there was no time separation between the pulses than the corresponding monophase pulse. Increasing separation time intervals increased strains, albeit non-uniformly. Acceleration followed by deceleration pulse produced greater strains in all regions than the other form of biphasic pulse. Thus, pulse shape appears to have an effect on regional strains in the brain.
认识到角向载荷与脑损伤之间的关联以及以往在动物、物理和实验模型中应用双相载荷的研究存在不一致性，本研究考察了加速 - 减速脉冲形状对特定区域应变的作用。使用了一个经过实验验证的二维有限元模型来模拟成年男性的头部。该模型将颅骨和大脑镰模拟为线性弹性材料，脑脊液模拟为流体动力学材料，大脑模拟为线性粘弹性材料。角向载荷矩阵包括围绕旋转中心在冠状面的旋转，即仅加速（持续时间4.5毫秒，峰值7.8弧度/秒²）、仅减速（20毫秒，峰值1.4弧度/秒²）、加速 - 减速以及减速 - 加速脉冲。两个双相脉冲的峰值之间的间隔范围为0至25毫秒。在胼胝体、中央后沟底部和顶叶的大脑皮层处测定主应变。将大脑划分为17个区域，并确定平均最大主应变的峰值。在所有模拟中，胼胝体的应变最高。在所有模拟中，顶叶下部的应变最小。在所有区域，单相脉冲的峰值应变相同，这表明角速度可能比峰值加速度或减速度是更好的度量指标。相比之下，对于双相脉冲，峰值应变具有区域和脉冲形状特异性。当脉冲之间没有时间间隔时，两个双相脉冲的峰值均低于相应的单相脉冲。增加间隔时间会增加应变，尽管并不均匀。先加速后减速的脉冲在所有区域产生的应变都比另一种双相脉冲形式更大。因此，脉冲形状似乎对大脑中的区域应变有影响。
