Ravazzani Paolo, Ruohonen Jarmo, Tognola Gabriella, Anfosso Federica, Ollikainen Marko, Ilmoniemi Risto J, Grandori Ferdinando
Centro di Ingegneria Biomedica CNR, Milan, Italy.
IEEE Trans Biomed Eng. 2002 May;49(5):463-71. doi: 10.1109/10.995685.
Magnetic stimulation of the nervous system is a non-invasive technique with a large number of applications in neurological diagnosis, brain research, and, recently, therapy. New applications require engineering modifications in order to decrease power consumption and coil heating. This can be accomplished by optimized coils with minimized resistance. In this study the influence of some frequency-related effects (skin and proximity effect) on the coil resistance will be discussed, together with the role played by wire shape, wire section, and twisting effect. The results show that the coil resistance increases with frequency. As an example, for a 20-mm2 circular wire section, the skin effect in the typical frequency range of magnetic stimulator devices (2-4 kHz) increases the coil resistance up to about 45% with respect to its dc value. Moreover, the influence of the frequency is lower for flat wire sections and reasonably small helix twist angle of the coil.
神经系统的磁刺激是一种非侵入性技术，在神经诊断、脑研究以及最近的治疗方面有大量应用。新的应用需要进行工程改进，以降低功耗和线圈发热。这可以通过电阻最小化的优化线圈来实现。在本研究中，将讨论一些与频率相关的效应（趋肤效应和邻近效应）对线圈电阻的影响，以及导线形状、导线截面和扭曲效应所起的作用。结果表明，线圈电阻随频率增加。例如，对于20平方毫米的圆形导线截面，在磁刺激器设备的典型频率范围（2 - 4千赫）内，趋肤效应使线圈电阻相对于其直流值增加高达约45%。此外，对于扁平导线截面和线圈合理小的螺旋扭曲角，频率的影响较小。
