经颅磁刺激聚焦场设计与仿真

发布时间：2018-08-28 10:32

【摘要】：经颅磁刺激（TMS）是一种作用于中枢神经系统的非侵入式刺激技术，它利用时变磁场，在目标区域中感应出感生电场，从而改变细胞膜内外电位差达到引起组织细胞兴奋地目的。由于颅骨对磁场具有通透性，磁场能直接穿过头皮和颅骨刺激深部神经组织。相比于传统的电极刺激方式，磁刺激具有更大的优势，其无创伤性、安全性、方便性、易于重复操作等优点，在临床上的应用研究越来越广泛。但现有的系统体积庞大、成本过高、刺激线圈磁聚焦效果差等缺点，限制了经颅磁刺激在临床上的应用，这些都是经颅磁刺激技术待解决的问题。为了实现磁聚焦，本文构建了分别包括8个子线圈和20个子线圈的圆环面线圈阵列模型。因影响磁聚焦的因素很多，解空间较大，本文提出利用群集智能优化算法优化线圈模型的方法。在基本粒子群优化算法和标准遗传优化算法的基础上，提出改进的混合遗传-粒子群算法，并用测试函数测试算法收敛于全局最优解的效率和成功率。结果表明，改进后的混合遗传-粒子群算法性能良好，在收敛速度和收敛率上有明显的优势。最后用该算法对影响线圈阵列模型磁聚焦性的各种参数进行优化求解，并将优化结果与传统的8字形线圈比较，结果显示，两种线圈阵列模型均有良好的磁聚焦性，20个子线圈的圆环面线圈模型基本上实现了点聚焦。另一方面，本文详细介绍了经颅磁刺激的生理基础和物理学原理、经颅磁刺激激励源系统的工作机理，对激励系统中影响感应磁场强度的因素进行分析，并得出结论，刺激线圈中电流的变化率和电流大小直接影响感应磁场强度和感生电场大小。在此基础上设计并实现了实际硬件电路，包括高压主回路、整流滤波电路、控制回路等，详细分析了电路中各参数对系统安全性、稳定性、磁场能量的影响，并提出改进方案。最后在180V电源电压供电情况下，，刺激线圈中获得峰值为320A，脉宽400us的脉冲电流，电流变化速度快，实现了脉冲大电流的产生。对获得的电流进行频谱分析，其主要能量集中在0-20kHz。本文对目前经颅磁刺激系统的缺点提出了改进的方案，对经颅磁刺激技术的发展有一定的指导作用。
[Abstract]:Transcranial magnetic stimulation (TMS) is a non-invasive stimulation technique acting on the central nervous system. It uses time-varying magnetic field and induces induced electric field in the target region, thus changing the potential difference between the cell membrane and the cell membrane to induce excitatory effect of tissue and cell. Because of the permeability of skull to magnetic field, magnetic field can directly penetrate the scalp and skull to stimulate deep nerve tissue. Compared with the traditional electrode stimulation, magnetic stimulation has more advantages, such as non-invasive, safe, convenient, easy to repeat, and so on. However, the large volume, high cost and poor magnetic focusing effect of the current system limit the clinical application of transcranial magnetic stimulation, which are the problems to be solved by transcranial magnetic stimulation. In order to realize magnetic focusing, a toroidal coil array model including 8 subcoils and 20 subcoils is constructed in this paper. Because there are many factors affecting magnetic focusing and the solution space is large, a method of optimizing coil model by cluster intelligence optimization algorithm is proposed in this paper. Based on the basic particle swarm optimization algorithm and the standard genetic optimization algorithm, an improved hybrid genetic particle swarm optimization algorithm is proposed. The efficiency and success rate of the algorithm converging to the global optimal solution are tested by the test function. The results show that the improved hybrid genetic particle swarm optimization algorithm has good performance and has obvious advantages in convergence speed and convergence rate. Finally, the algorithm is used to optimize the parameters that affect the magnetic focusing of the coil array model, and the optimization results are compared with the traditional 8-shaped coil. The results show that, Both kinds of coil array models have good magnetic focusing. The toroidal coil model of 20 subcoils basically realizes point focusing. On the other hand, the physiological basis and physics principle of transcranial magnetic stimulation and the working mechanism of transcranial magnetic stimulation source system are introduced in detail. The factors influencing the magnetic field intensity in the excitation system are analyzed, and the conclusion is drawn. The rate of change of the current and the magnitude of the current in the stimulus coil directly affect the induced magnetic field intensity and the induced electric field. On this basis, a practical hardware circuit is designed and implemented, including high voltage main circuit, rectifier filter circuit, control circuit and so on. The effects of various parameters in the circuit on system security, stability and magnetic field energy are analyzed in detail, and an improved scheme is put forward. Finally, under the condition of 180 V power supply, the pulse current with peak value of 320A and pulse width 400us is obtained in the stimulus coil. The speed of current change is fast, and the large pulse current is generated. The main energy of the obtained current is focused on 0-20 kHz. In this paper, an improved scheme is proposed for the shortcomings of transcranial magnetic stimulation system, which can guide the development of transcranial magnetic stimulation technology.
【学位授予单位】：成都信息工程学院
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R312;TP18

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