Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida, USA.
J Neurotrauma. 2012 Jan 20;29(2):418-29. doi: 10.1089/neu.2011.1772. Epub 2011 Nov 8.
Blast-induced traumatic brain injury (bTBI) has received increasing attention in recent years due to ongoing military operations in Iraq and Afghanistan. Sudden impacts or explosive blasts generate stress and pressure waves that propagate at high velocities and affect sensitive neurological tissues. The immediate soft tissue response to these stress waves is difficult to assess using current in vivo imaging technologies. However, these stress waves and resultant stretching and shearing of tissue within the nano- to microsecond time scale of blast and impact are likely to cause initial injury. To visualize the effects of stress wave loading, we have developed a new ex vivo model in which living tissue slices from rat brain, attached to a ballistic gelatin substrate, were subjected to high-strain-rate loads using a polymer split Hopkinson pressure bar (PSHPB) with real-time high-speed imaging. In this study, average peak fluid pressure within the test chamber reached a value of 1584±63.3 psi. Cavitation due to a trailing underpressure wave was also observed. Time-resolved images of tissue deformation were collected and large maximum eigenstrains (0.03-0.42), minimum eigenstrains (-0.33 to -0.03), maximum shear strains (0.09-0.45), and strain rates (8.4×10³/sec) were estimated using digital image correlation (DIC). Injury at 4 and 6 h was quantified using Fluoro-Jade C. Neuronal injury due to PSHPB testing was found to be significantly greater than injury associated with the tissue slice paradigm alone. While large pressures and strains were encountered for these tests, this system provides a controllable test environment to study injury to submerged brain slices over a range of strain rate, pressure, and strain loads.
爆炸所致创伤性脑损伤（bTBI）近年来受到越来越多的关注，这是由于在伊拉克和阿富汗持续的军事行动。突然的冲击或爆炸产生的应力和压力波以高速传播，并影响敏感的神经组织。目前的体内成像技术很难评估这些应力波对软组织的即时反应。然而，这些应力波和组织在纳秒到微秒时间尺度内的拉伸和剪切，很可能导致初始损伤。为了观察应力波加载的影响，我们开发了一种新的离体模型，其中来自大鼠大脑的活体组织切片附着在弹道明胶基质上，使用聚合物分离 Hopkinson 压力杆（PSHPB）以高应变速率加载，并进行实时高速成像。在这项研究中，测试室内的平均峰值流体压力达到 1584±63.3psi。还观察到由于尾流负压波引起的空化。收集了组织变形的时变图像，并使用数字图像相关（DIC）估计了大的主应变（0.03-0.42）、最小主应变（-0.33 到-0.03）、最大剪应变（0.09-0.45）和应变率（8.4×10³/sec）。使用 Fluoro-Jade C 量化了 4 和 6 小时的损伤。PSHPB 测试引起的神经元损伤明显大于单独组织切片范式引起的损伤。虽然这些测试遇到了较大的压力和应变，但该系统提供了一个可控的测试环境，可用于研究在不同应变率、压力和应变载荷下对浸没在水中的脑切片的损伤。
