Section for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs, Lyngby, Denmark; MagVenture A/S, Farum, Denmark; Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark.
MagVenture A/S, Farum, Denmark.
Brain Stimul. 2022 May-Jun;15(3):697-706. doi: 10.1016/j.brs.2022.04.017. Epub 2022 Apr 28.
The effects of transcranial magnetic stimulation (TMS) on brain activity depend on the design of the stimulation coil. A wide range of coils from different vendors are currently used with different stimulation properties. This decreases the comparability of study results.
To systematically compare widely used commercial TMS coils concerning their focality, stimulation depth and efficacy. To provide validated models and data of these coils for accurate simulations of the induced electric fields.
We reconstructed the magnetic vector potential of 25 commercially available TMS coils of different vendors from measurements of their magnetic fields. Most coils had a figure-of-eight configuration. We employed the reconstructed magnetic vector potential in simulations of the electric field in a spherical head model. We estimated the motor thresholds of the coil-stimulator combinations using the calculated fields, the pulse waveforms and a leaky integrator model of the neural membrane.
Our results confirm a previously reported systematic trade-off between focality and relative depth of stimulation. However, neither the peak field strength in the "cortex" of the sphere model nor the estimated motor thresholds were strongly related to the two former measures and need to be additionally determined.
Our comprehensive coil characterization facilitates objective comparisons of coils of different sizes and from different vendors. The models and auxiliary data will be made available for electric field simulations in SimNIBS. Our work will support TMS users making an informed selection of a suited coil for a specific application and will help to reduce uncertainty regarding the TMS-induced electric field in the brain target region.
经颅磁刺激（TMS）对大脑活动的影响取决于刺激线圈的设计。目前，不同供应商生产的各种刺激线圈具有不同的刺激特性，这降低了研究结果的可比性。
系统比较广泛使用的商业 TMS 线圈在聚焦性、刺激深度和效果方面的差异。为了对诱导电场进行精确模拟，提供这些线圈的经过验证的模型和数据。
我们从磁场测量中重建了 25 个不同供应商的商业 TMS 线圈的磁矢量位。大多数线圈具有八字形配置。我们在球形头部模型中使用重建的磁矢量位模拟电场。我们使用计算出的场、脉冲波形和神经膜的漏电积分器模型来估计线圈-刺激器组合的运动阈值。
我们的结果证实了先前报道的聚焦性和相对刺激深度之间的系统权衡。然而，球模型“皮层”中的峰值场强或估计的运动阈值与前两个测量值没有很强的相关性，需要额外确定。
我们全面的线圈特性描述有助于对不同尺寸和供应商的线圈进行客观比较。该模型和辅助数据将可用于 SimNIBS 中的电场模拟。我们的工作将支持 TMS 用户根据特定应用选择合适的线圈，并有助于降低对大脑目标区域 TMS 诱导电场的不确定性。
