Abstract：
Transcranial magnetic stimulation (TMS) is a non-invasive method for stimulating the cortex. Concurrent functional magnetic resonance imaging can show changes in TMS-induced activity in the whole brain, with the potential to inform brain function research and to guide the development of TMS therapy. However, the interaction of the strong current pulses in the TMS coil in the static main magnetic field of the MRI produces high Lorentz forces, which may damage the coil enclosure and compromise the patient\'s safety. We studied the time-dependent mechanical behavior and durability of two multi-locus TMS (mTMS) coil arrays inside a high-field MRI bore with finite element modeling. In addition, coil arrays were built and tested based on the simulation results. We found that the current pulses produce shock waves and time-dependent stress distribution in the coil plates. The intensity and location of the maximum stress depend on the current waveform, the coil combination, and the transducer orientation relative to the MRI magnetic field. We found that 30% glass-fiber-filled polyamide is the most durable material out of the six options studied. In addition, novel insights for more durable TMS coil designs were obtained. Our study contributes to a comprehensive understanding of the underlying mechanisms responsible for the structural failure of mTMS coil arrays during stimulation within high static magnetic fields. This knowledge is essential for developing mechanically stable and safe mTMS-MRI transducers.
摘要：
经颅磁刺激（TMS）是一种用于刺激皮质的非侵入性方法。同时功能磁共振成像（fMRI）可以显示TMS引起的整个大脑活动的变化，有可能为脑功能研究提供信息，并指导TMS治疗的发展。然而,TMS线圈中的强电流脉冲在MRI的静态主磁场中的相互作用产生高洛伦兹力，这可能会损坏线圈外壳并危及患者的安全。我们通过有限元建模研究了高场MRI孔内两个多位点TMS线圈阵列的随时间变化的力学行为和耐久性。此外,线圈阵列的建立和测试的基础上，仿真结果。我们发现电流脉冲在线圈板中产生冲击波和随时间变化的应力分布。最大应力的强度和位置取决于电流波形，线圈组合，和换能器相对于MRI磁场的方向。我们发现，在所研究的六种选择中，30%的玻璃纤维填充聚酰胺是最耐用的材料。此外,获得了更耐用的TMS线圈设计的新见解。我们的研究有助于全面了解在高静磁场刺激期间mTMS线圈阵列结构失效的潜在机制。这些知识对于开发机械稳定和安全的mTMS-MRI换能器至关重要。
