基于真实颅脑结构建模的经颅磁刺激仿真分析

发布时间：2018-04-27 00:14

本文选题：经颅磁刺激 + 有限元分析　；参考：《北京协和医学院》2017年博士论文

【摘要】：经颅磁刺激(TMS)技术是一种无痛、无创、相对安全的神经调节技术,通过脉冲电流产生的时变磁场,透过颅脑结构外部组织,直接在脑神经产生电生理干预,目前广泛应用于多种神经系统疾病、精神疾病的临床诊断与治疗,以及脑科学与认知科学领域中的探索性研究。刺激线圈是TMS技术实现的重要载体,其形状和尺寸限定了空间内感应电场的分布情况,直接对使用效果造成影响。研究刺激线圈产生的效果主要从两个方面进行,一个是其自身的电磁场特性,另一个是其作用到脑之后的实际效果。前者可以通过电磁场检测和简单的建模仿真来实现;而后者一般很难在生物体颅脑结构中直接测量,通常会采用间接的手段,如MEP,以及一些复杂的建模仿真运算。此外,动物实验也是TMS重要研究手段之一。在TMS建模仿真研究中,目前常见的颅脑结构模型主要包括头皮、颅骨、脑脊液、脑灰质和脑白质等组织,对于脑深部结构的重建比较少见。在仿真过程中,常见的8字形线圈模型多为近似几何结构,仿真结果感应电磁场分布与真实线圈存在差别。TMS作用在复杂颅脑组织时,刺激效果常用半宽度区面积(聚焦面积)进行计算,对于真实有效作用面积的研究和探讨比较缺乏。此外,TMS动物实验相关仿真研究也并不多见。为进一步提高TMS建模仿真研究的真实性和指导价值,本文主要建立一套完善的建模仿真研究方法以及刺激效果计算方法。本文方法可应用于计算TMS人体实验、临床使用和动物实验中感应电磁场的分布规律,评价刺激效果,仿真研究结果可为TMS应用领域提供重要的理论依据。本文首先利用MIMICS重建了特定受试者的真实颅脑结构模型,包括丘脑、边缘系统、脑室等脑深部组织结构,以及具有真实结构的8字线圈模型,然后利用ANSYS实现复杂结构有限元仿真分析。在仿真过程中,本文使用盐水槽检测实验来对仿真参数进行校正,使仿真结果与真实情况具有可比性。本文还在真实颅脑结构模型下,通过仿真对比TMS和DES感应电场分布,提出了计算刺激有效区面积的方法,并找出二者有效区之间的关系,为TMS实现精准定位,提供了方法和理论支持。最后,本文利用上述方法重建了 WISTAR大鼠颅脑结构模型和动物线圈模型,研究讨论了 TMS动物实验中刺激有效区面积随刺激强度的变化规律。经过计算,TMS作用于人体颅脑结构时有效区面积相当于聚焦面积的约14%,作用于大鼠颅脑结构时有效区面积相当于聚焦面积计算结果的约63%。该方法为TMS临床使用和动物实验过程中中实现精准定位奠定了基础。
[Abstract]:Transcranial magnetic stimulation (TMS) is a painless, noninvasive and relatively safe technique for neuroregulation, which directly interferes in the brain nerve through the time-varying magnetic field produced by the pulse current and through the external tissue of the craniocerebral structure. At present, it is widely used in the clinical diagnosis and treatment of various nervous system diseases, mental diseases, as well as the exploratory research in the field of brain science and cognitive science. The stimulus coil is an important carrier of TMS technology. Its shape and size limit the distribution of the inductive electric field in the space, which has a direct impact on the application effect. The effect of stimulation coil is studied from two aspects, one is its own electromagnetic properties, the other is the actual effect after it acts on the brain. The former can be realized by electromagnetic field detection and simple modeling and simulation, while the latter is difficult to measure directly in the brain structure of organism, and usually uses indirect means, such as MEP, and some complex modeling and simulation operations. In addition, animal experiments are also one of the important research methods of TMS. In the research of TMS modeling and simulation, the common craniocerebral structure models mainly include scalp, skull, cerebrospinal fluid, gray matter and white matter, etc. In the process of simulation, the most common 8-shaped coil models are approximate geometric structure. The simulation results show that the electromagnetic field distribution is different from the real coil. TMS acts on complex brain tissue. The half width area (focus area) is commonly used to calculate the stimulation effect, but the study and discussion of the real effective area is scarce. In addition, there are few related simulation studies on TMS animal experiments. In order to further improve the authenticity and guiding value of TMS modeling and simulation research, this paper mainly establishes a set of perfect modeling and simulation research method and stimulation effect calculation method. This method can be used to calculate the distribution of induction electromagnetic field in TMS human experiment, clinical use and animal experiment, and to evaluate the stimulation effect. The simulation results can provide an important theoretical basis for the application of TMS. In this paper, MIMICS was used to reconstruct the real brain structure model of specific subjects, including thalamus, limbic system, ventricle and other deep brain tissue structures, as well as 8-character coil model with real structure. Then the finite element analysis of complex structure is realized by ANSYS. In the process of simulation, the salt flume testing experiment is used to correct the simulation parameters, so that the simulation results are comparable with the real situation. In this paper, under the real brain structure model, by comparing the distribution of induced electric field between TMS and DES, we put forward a method to calculate the effective area of stimulation, and find out the relationship between the effective area and the effective area, so as to realize the accurate location for TMS. The method and theory support are provided. Finally, the craniocerebral structure model and the animal coil model of WISTAR rats were reconstructed by the above methods, and the changes of the effective area of stimulation with the intensity of stimulation in TMS animal experiment were studied and discussed. The effective area of TMS acting on the human brain structure is about 14% of the focus area, and the effective area area of the brain structure acting on the rat brain structure is about 63% of the focus area. This method lays a foundation for accurate positioning in clinical use and animal experiment of TMS.
【学位授予单位】：北京协和医学院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TP391.9;R741.044

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