Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
Brain Stimul. 2022 Jan-Feb;15(1):116-124. doi: 10.1016/j.brs.2021.11.014. Epub 2021 Nov 21.
Transcranial magnetic stimulation (TMS) allows non-invasive stimulation of the cortex. In multi-locus TMS (mTMS), the stimulating electric field (E-field) is controlled electronically without coil movement by adjusting currents in the coils of a transducer.
To develop an mTMS system that allows adjusting the location and orientation of the E-field maximum within a cortical region.
We designed and manufactured a planar 5-coil mTMS transducer to allow controlling the maximum of the induced E-field within a cortical region approximately 30 mm in diameter. We developed electronics with a design consisting of independently controlled H-bridge circuits to drive up to six TMS coils. To control the hardware, we programmed software that runs on a field-programmable gate array and a computer. To induce the desired E-field in the cortex, we developed an optimization method to calculate the currents needed in the coils. We characterized the mTMS system and conducted a proof-of-concept motor-mapping experiment on a healthy volunteer. In the motor mapping, we kept the transducer placement fixed while electronically shifting the E-field maximum on the precentral gyrus and measuring electromyography from the contralateral hand.
The transducer consists of an oval coil, two figure-of-eight coils, and two four-leaf-clover coils stacked on top of each other. The technical characterization indicated that the mTMS system performs as designed. The measured motor evoked potential amplitudes varied consistently as a function of the location of the E-field maximum.
The developed mTMS system enables electronically targeted brain stimulation within a cortical region.
经颅磁刺激（TMS）允许对皮质进行非侵入性刺激。在多点 TMS（mTMS）中，通过调整换能器线圈中的电流，电子控制刺激电场（E 场），而无需线圈移动。
开发一种 mTMS 系统，该系统允许在皮质区域内调整 E 场最大值的位置和方向。
我们设计并制造了一个平面 5 线圈 mTMS 换能器，以允许在直径约 30mm 的皮质区域内控制感应 E 场的最大值。我们开发了具有独立控制 H 桥电路设计的电子设备，以驱动多达六个 TMS 线圈。为了控制硬件，我们编写了在现场可编程门阵列和计算机上运行的软件。为了在皮质中产生所需的 E 场，我们开发了一种优化方法来计算线圈中所需的电流。我们对 mTMS 系统进行了特性描述，并在健康志愿者中进行了电机映射实验的概念验证。在电机映射中，我们保持换能器放置固定，而在中央前回上电子地移动 E 场最大值，并测量对侧手部的肌电图。
换能器由一个椭圆形线圈、两个八字形线圈和两个四叶形线圈堆叠而成。技术特性表明，mTMS 系统按设计运行。测量的运动诱发电位幅度随着 E 场最大值的位置而一致变化。
开发的 mTMS 系统能够在皮质区域内进行电子靶向脑刺激。
