四层复杂球颅脑模型的构建

Establishment of a Four Layer Complicated Ellipsoid Brain Model

颅脑模型构建的研究是颅内成像的基础,也是磁感应断层成像(MIT)系统设计中正问题计算的必要条件。根据人体颅脑真实结构,通过Comsol Multiphysics有限元数值仿真软件的几何建模工具,构建近似真实颅脑结构的四层复杂球颅脑模型。首先,根据大脑体积和颅骨内径,构建脑实质模型;其次,根据人体解剖结构,构建颅骨模型,并进行枕骨修正、轮廓修正、额骨修正和眼眶修正;第三,通过对颅骨模型的缩放,构成头皮层、颅骨层、脊液层,并与脑实质模型共同构成具有4层结构的颅脑模型;最后,将模型置入10 MHz的交流磁场中,通过仿真计算获得头皮层、颅骨层、脊液层和脑实质层感应电流的分布,感应电流在脊液层最强,在皮肤层和脑实质层较弱,在颅骨层最弱,且各层感应电流密度值之比为32∶1∶190∶21,与电导率之比相近。结果表明,该模型可以很好地显示出人体头部各组织的电磁特性差异,为MIT系统研究提供可靠的依据。

The study of brain model establishment is the basis of intracranial imaging, and it is also the necessary condition for the calculation of forward problem solution in the magnetic induction tomography （MIT） system. According to the brain structure, a four layers complicated ellipsoid brain model was established through a finite element simulation software Comsol Multiphysics. Firstly, the brain parenchyma model was constructed according to the brain volume and the skull inner diameter. Secondly, the skull model was constructed according to the human anatomy structureand the contour, occipital, frontal and orbit of the model were corrected. Thirdly, the head cortex, skull and spinal fluid layer were constituted by scale model of the skull, and the four layers brain model were constituted together with the brain parenchyma layer. Finally, put the model into alternating current magnetic field of 10 MHz, and gave the induced current distribution of scalp layer, skull layer, spinal fluid layer and parenchymal layer. The induced current was strongest in the spinal fluid layer and weaker in the skin layer and the parenchymal layer, while was the weakest in the skull layer. The ratio of the induced current density values in each layer was 32：1：190：21, closed to the ratio of electrical conductivity. The simulation experimental results showed that the model could display the difference of the electromagnetic characteristics of human head tissues, providing reliable data for MIT system.