经颅磁刺激中刺激线圈的仿真研究

Simulationstudy on coils for transcranial magnetic stimulation

目的设计用于经颅磁刺激的线圈,要求能够对大脑皮质进行多点刺激,且具有聚焦性好、制作简单、使用方便等特点。方法利用电磁仿真方法,以圆形线圈和8字形线圈为基础,计算线圈在均匀人体模型中感应电场的分布情况,比较尺寸、绕法对经颅磁刺激线圈的聚焦性和刺激深度的影响。在此基础上设计了一种多圆相切线圈,并计算该线圈在均匀人体和真实头部模型中的电场分布。结果感应电场强度随刺激深度的增加呈指数式衰减。减小圆形线圈的尺寸,会提高聚焦性,同时可减弱感应电场强度。8字形线圈比圆形线圈具有更好的聚焦性,多层绕法综合效果较好。多圆相切线圈具有8字形线圈的优点,且可以进行多点刺激。结论尺寸、绕法等因素对线圈的聚焦性和刺激深度具有重要影响,多圆相切线圈在经颅磁刺激中具有很好的应用前景。真实头部模型仿真,对于线圈的设计和靶区定位具有重要意义。

Objective To design a new type of coil for transcranial magnetic stimulation （TMS）, which can stimulate the cerebral cortex on muhipoint with good focusing property and is simple to make and convenient to use. Methods Circular coils and figure-8 coils were simulated using electromagnetic simulation methods. The distribution of the coil-induced electric field in homogeneous phantom was computed. The impact of coil size and winding on the focusability and stimulation depth of TMS coils were analyzed. On this basis,a new type of coil named multi-circle tangent coil （MTC） was designed, and the distribution of MTC-induced electric field in homogeneous phantom model and realistic human head model was computed. Results With the increase of stimulation depth,there was an exponential decay in the intensity of the induced electric field. Smaller circular coils produced higher foeusability and lower intensity of induced electric field. The focusability of figure-8 coils was higher than that of circular coils. The comprehensive effect of multi-layer winding method was preferable. MTC supported muhipoint stimulation in addition to owning the advantages of figure-8 coils. Conclusions Factors such as size and winding have a big influence on the focusability and stimulation depth of coils. MTC has an exciting application prospect in TMS. Simulation on realistic human head model is of great significance for coil design and target location.