脑震荡致伤机理的参数化有限元仿真研究

Researches have been reported that short term coma, loss of consciousness and loss of memory due to traumatic concussion were closely related to the damages of hippocampus, thalamus, diencephalon and other white matter in deep of the brain because of external loads. Based on this hypothesis, 4 new modified finite element human head models for the 5th, 50th, 95thpercentile adult and 6-year old child heads are proposing. These models will be built upon the previously published high biofidelic finite element models of the human heads, representing the 5th, 50th, 95thpercentile adult and 6-year old child heads, by deep diving into the internal structures of the brains such as the corpus callosum, the third ventricle, hippocampus, diencephalon, thalamus, mid-brain, pons and other white matter. The accurate anatomical boundaries of these organs will be extracted from the original CT scan images for which these 4 models were first developed. Impact simulations under various loading conditions and parametric studies will be performed using the newly created 4 models through non-linear large deformation finite element computation and analysis. Injury responses from those deep brain organs as mentioned above will be investigated further by tissue-level stress-strain analysis. The relationship between external loading conditions and tissue-level stress-strain will be simulated and analyzed; variation trends between external loads and tissue-level stress-strain among the 4 models will be studied; factors affect traumatic concussion will be identified and injury mechanisms will be proposed; injury criterion for concussion will be established; and finally finite element model-based traumatic concussion assessment system will be proposed.

研究表明，因脑震荡引起的暂短昏迷、意识丧失和记忆缺失与海马体、丘脑、间脑和其他脑白质等深度脑器官受损密切相关。基于这种假设，本项目在本课题组已研发的具有高仿真解剖结构的中国人第5、50、95百分位和6岁儿童的头部有限元模型基础上，针对原始模型的CT医学扫描影像，进一步深耕，对大脑深部器官如胼胝体、第三脑室、海马体、丘脑、中脑、脑桥等器官重构其准确解剖位置，并重新进行精准的模型建设。通过对重新构建的4个模型的非线性、大变形有限元法计算和参数化分析，求解不同个体头部在不同外载撞击条件下大脑深处的损伤响应。模拟、分析大脑深处的胼胝体、丘脑、海马体等和其他脑白质在外载荷下与生物组织层次的应力-应变响应关系；寻找这些应力、应变与外在撞击载荷的变化规律；从而认识脑震荡的发生规律，探讨脑震荡的致伤机理；进而提出脑震荡损伤判断准则；最后建立以有限元模型为基础的脑震荡损伤评估体系。

因脑震荡引起的暂短昏迷、意识丧失和记忆缺失与海马体、丘脑、间脑和其他脑白质等深度脑器官受损密切相关。本项目在本课题组已研发的具有高仿真解剖结构的中国人第5、50、95百分位、1岁、3岁和6岁儿童的头部有限元模型基础上，对大脑深部器官如胼胝体、第三脑室、海马体、丘脑、中脑、脑桥等器官重构其准确解剖位置，并重新构建了具有精准脑深部结构的头部系列有限元模型。基于所构建的模型，参考现有的已公开发表的尸体实验数据，对系列模型在各种工况下的有效性进行了重新验证。通过对重新构建的系列模型的非线性、大变形有限元法计算和参数化分析，求解不同个体头部在不同外载撞击条件下大脑深处的损伤响应。模拟、分析大脑深处的胼胝体、丘脑、海马体等和其他脑白质在外载荷下与生物组织层次的应力-应变响应关系。重构了尸体头部跌落和旋转试验，分析了头部在直线运动和旋转运动中颅脑损伤机理的不同。研究了颅骨、脑脊液和脑组织之间不同接触面类型和不同脑脊液划分密度对脑损伤预测的影响；研究结果发现，不同的接触界面类型导致撞击侧不同的颅骨变形和直线加速度，共节点接触模型仿真实验结果与尸体试验结果相关性最高，说明模型能够更加精确的预测脑损伤。基于构建的系列模型，重构了现实碰撞中头部发生外伤性脑损伤的真实案例，从而获得了不同年龄段中头部不同尺寸、形状和脑组织材料参数对脑组织应变以及脑损伤预测的影响。建议有必要从真实的CT数据或MRI影像建立儿童头部有限元模型，而不是通过缩放的方法预测儿童脑损伤风险。提取NHTSA数据库的6岁儿童汽车前碰撞仿真实验中儿童头部的动力学参数，加载到具有真实解剖学结构的6岁儿童头部有限元模型刚性颅骨上，探讨车辆前碰撞过程中，儿童头部脑组织生物力学响应以及动力学参数与头部各损伤指标的相关性；结果发现前碰撞事故中，头部主要沿矢状面旋转，脑干区域经历两次较明显的拉伸运动。头部经历的角加速度与脑组织最大主应变相关性较好。