梗阻性脑积水侧脑室及室周脑组织生物力学响应的有限元分析

目的运用有限元方法对梗阻性脑积水进行计算机模拟,研究分析侧脑室及室周脑组织的生物力学响应及其所产生的病理生理影响。方法依据正常国人颅脑MRI轴位T2加权图像获取解剖信息,在有限元软件ANSYS中生成包含侧脑室前、后角和体部的半侧脑层面的二维有限元模型。模拟脑组织为固、液两相物质组成的线性多孔弹性材料,设定生物力学特性参数及边界条件和初始条件,施加载荷,运用有限元软件ABAQUS进行计算求解,以云图形式输出结果。结果有限元模型动态模拟了梗阻性脑积水侧脑室各部的扩张过程,直观显示出各个时间步室周脑组织内的应力类型及分布、各部的应变和位移。结论膨胀性应力集中引起角部脑水肿;梗阻性脑积水早期侧脑室角部形态变化最明显;体部附近脑组织结构容易受压移位。这些生物力学响应是室内压增高的结果,也与侧脑室的解剖形态密切相关。

A finite-element analysis of biomechanics responses of lateral ventricle and periventricular brain tissues owing to obstructive hydrocephalus

Objective A computer simulation of obstructive hydrocephalus based on the finite-element method was used to study the biomechanics responses of lateral ventricle and periventricular tissues, and the pathophysiological effects. Methods The anatomic information needed to construct the finite-element model for simulation was obtained from T2-weighted axial magnetic resonance imaging scans of a normal volunteer man. Only one-half of the slice including anterior and posterior horns and body of ventricle was used, given the symmetry of the brain in that section. A two-dimensional finite element model was constructed by the finite element software ANSYS. Brain parenchyma was modeled as a two-phase material composed of a porous elastic matrix saturated by interstitial fluid. The specific material properties of brain tissues were defined, as well as the boundary conditions and the loads, then calculations were peformed by using ABAQUS, the results were exported in the form of nephograms. Results The results of the finite-element simulation showed the dynamic progression of obstructive hydrocephalus, including displacement of ventricular dilation, the distribution of stress and strain in the periventricular brain tissues at every time step. Conclusions Expansive stress concentrations have the effect of inducing brain edema around horns; The visible changes of configuration can be found at the horns in the early stages of obstructive hydrocephalus, owing to maximum strain changes occurring around the homs; The brain tissues around ventricular body shift severely because of compression. These changes are results not only of increased intraventricular pressure but also of ventricular geometry.