Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland.
J Neural Eng. 2021 Nov 12;18(6). doi: 10.1088/1741-2552/ac3207.
. Coils designed for transcranial magnetic stimulation (TMS) must incorporate trade-offs between the required electrical power or energy, focality and depth penetration of the induced electric field (E-field), coil size, and mechanical properties of the coil, as all of them cannot be optimally met at the same time. In multi-locus TMS (mTMS), a transducer consisting of several coils allows electronically targeted stimulation of the cortex without physically moving a coil. In this study, we aimed to investigate the relationship between the number of coils in an mTMS transducer, the focality of the induced E-field, and the extent of the cortical region within which the location and orientation of the maximum of the induced E-field can be controlled.We applied convex optimization to design planar and spherically curved mTMS transducers of different E-field focalities and analyzed their properties. We characterized the trade-off between the focality of the induced E-field and the extent of the cortical region that can be stimulated with an mTMS transducer with a given number of coils.At the expense of the E-field focality, one can, with the same number of coils, design an mTMS transducer that can control the location and orientation of the peak of the induced E-field within a wider cortical region.. With E-fields of moderate focality, the problem of electronically targeted TMS becomes considerably easier compared with highly focal E-fields; this may speed up the development of mTMS and the emergence of new clinical and research applications.
. 用于经颅磁刺激 (TMS) 的线圈必须在所需的电力或能量、诱导电场 (E 场) 的焦点和深度穿透、线圈尺寸以及线圈的机械性能之间进行权衡，因为它们都不能同时达到最佳状态。在多部位 TMS (mTMS) 中，由多个线圈组成的换能器允许通过电子方式靶向刺激皮层，而无需物理移动线圈。在这项研究中，我们旨在研究 mTMS 换能器中线圈的数量、诱导 E 场的焦点以及可以控制诱导 E 场最大值位置和方向的皮质区域的范围之间的关系。我们应用凸优化设计了具有不同 E 场焦点的平面和球形弯曲的 mTMS 换能器，并分析了它们的特性。我们描述了具有给定数量的线圈的 mTMS 换能器的诱导 E 场的焦点和可以刺激的皮质区域的范围之间的权衡。以牺牲 E 场焦点为代价，我们可以用相同数量的线圈设计一个 mTMS 换能器，该换能器可以控制在更大的皮质区域内诱导 E 场峰值的位置和方向。对于中等焦点的 E 场，与高焦点的 E 场相比，电子靶向 TMS 的问题变得相当容易；这可能会加快 mTMS 的发展和新的临床和研究应用的出现。
