Xu Bingyu, Lu Mai
Key Laboratory of Optoelectronic Technology and Intelligent Control of Ministry of Education, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China.
School of Automation and Electrical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2022 Aug 25;39(4):685-693. doi: 10.7507/1001-5515.202201030.
Currently, transcranial magnetic stimulation (TMS) has been widely used in the treatment of depression, Parkinson's disease and other neurological diseases. To be able to monitor the brain's internal activity during TMS in real time and achieve better treatment outcomes, the researchers proposed combining TMS with neuroimaging methods such as magnetic resonance imaging (MRI), both of which use Tesla-level magnetic fields. However, the combination of strong current, large magnetic field and small size is likely to bring physical concerns which can lead to mechanical and thermal instability. In this paper, the MRI static magnetic field, the TMS coil and human head model were built according to the actual situations. Through the coupling of the magnetic field and the heat transfer module in the finite element simulation software COMSOL, the force and temperature of the TMS coil and head were obtained when the TMS was used in combination with MRI (TMS-MRI technology). The results showed that in a 3 T MRI environment, the maximum force density on the coil could reach 2.51 × 10 N/m. Both the direction of the external magnetic field and the current direction in the coil affected the force distributions. The closer to the boundary of the external magnetic field, the greater the force. The magnetic field generated by the coil during TMS treatment increased the temperature of the brain tissue by about 0.16 °C, and the presence of the MRI static magnetic field did not cause additional thermal effects. The results of this paper can provide a reference for the development of the use guidelines and safety guidelines of TMS-MRI technology.
目前，经颅磁刺激（TMS）已广泛应用于抑郁症、帕金森病等神经疾病的治疗。为了能够在TMS治疗过程中实时监测大脑内部活动并取得更好的治疗效果，研究人员提出将TMS与磁共振成像（MRI）等神经成像方法相结合，这两种技术都使用特斯拉级别的磁场。然而，强电流、大磁场和小尺寸的结合可能会带来物理方面的问题，进而导致机械和热不稳定性。在本文中，根据实际情况构建了MRI静磁场、TMS线圈和人体头部模型。通过有限元模拟软件COMSOL中的磁场与传热模块的耦合，获得了TMS与MRI联合使用（TMS-MRI技术）时TMS线圈和头部的受力及温度情况。结果表明，在3 T的MRI环境中，线圈上的最大力密度可达2.51×10 N/m。外部磁场方向和线圈中的电流方向都会影响力的分布。越靠近外部磁场边界，力越大。TMS治疗过程中线圈产生的磁场使脑组织温度升高约0.16℃，而MRI静磁场的存在并未引起额外的热效应。本文的结果可为TMS-MRI技术使用指南和安全指南的制定提供参考。
