Tan Xinhua, Guo Ao, Tian Jiasheng, Li Yingwei, Shi Jian
School of Information Science and Engineering, Yanshan University, Qinhuangdao, China.
School of Electronic Information and Communications, Huazhong University of Science and Technology, Wuhan City, China.
Front Neurosci. 2025 Jan 7;18:1500619. doi: 10.3389/fnins.2024.1500619. eCollection 2024.
Transcranial magnetic stimulation (TMS) is widely used for the noninvasive activation of neurons in the human brain. It utilizes a pulsed magnetic field to induce electric pulses that act on the central nervous system, altering the membrane potential of nerve cells in the cerebral cortex to treat certain mental diseases. However, the effectiveness of TMS can be compromised by significant heat generation and the clicking noise produced by the pulse in the TMS coil. This study proposes a novel, non-resonant, high-frequency switching design controlled by high-frequency pulse-width modulation (PWM) voltage excitation to achieve ideal pulse-current waveforms that minimize both clicking noise and heat generation from the TMS coil.
First, a particle swarm optimization algorithm was used to optimize the pulse-current waveform, minimizing both the resistance loss and clicking noise (vibration energy) generated by the TMS coils. Next, the pulse-current waveform was modeled based on the principles of programmable transcranial magnetic stimulation circuits. The relationships between the parameters of the pulse-current waveform, vibration energy, and ohmic resistance loss in the TMS coil were explored, ensuring the necessary depolarization of the nerve membrane potential. Finally, four insulated-gate bipolar transistors, controlled by a series of PWM pulse sequences, generated the desired pulse-current duration and direction in the H-bridge circuit. The duration and slope of the rising and falling segments of the current waveform were adjusted by the PWM pulse duration.
The optimized current waveform, represented by three segmented functions, reduces heat loss and noise while inducing a greater change in neural membrane potential compared with those obtained with conventional symmetric waveforms. Spectral analysis further confirmed that the noise spectrum of the optimized current waveform, particularly the peak spectrum, is significantly lower than that of the conventional triangular symmetric waveform.
The study provide a method and new ideas for low energy consumption and low-noise transcranial magnetic stimulation by using TMS circuit design techniques as well as waveform optimization.
经颅磁刺激（TMS）被广泛用于无创激活人脑神经元。它利用脉冲磁场诱导作用于中枢神经系统的电脉冲，改变大脑皮层神经细胞的膜电位来治疗某些精神疾病。然而，TMS的有效性可能会受到大量发热以及TMS线圈中脉冲产生的咔嗒声噪声的影响。本研究提出一种新颖的、非谐振的、由高频脉宽调制（PWM）电压激励控制的高频开关设计，以实现理想的脉冲电流波形，从而将TMS线圈产生的咔嗒声噪声和发热降至最低。
首先，使用粒子群优化算法优化脉冲电流波形，将TMS线圈产生的电阻损耗和咔嗒声噪声（振动能量）降至最低。接下来，基于可编程经颅磁刺激电路的原理对脉冲电流波形进行建模。探索了脉冲电流波形参数、振动能量与TMS线圈中欧姆电阻损耗之间的关系，确保神经膜电位有必要的去极化。最后，由一系列PWM脉冲序列控制的四个绝缘栅双极晶体管在H桥电路中产生所需的脉冲电流持续时间和方向。电流波形上升和下降段的持续时间和斜率通过PWM脉冲持续时间进行调整。
由三个分段函数表示的优化电流波形减少了热损失和噪声，同时与传统对称波形相比，能引起神经膜电位更大的变化。频谱分析进一步证实，优化电流波形的噪声频谱，特别是峰值频谱，明显低于传统三角对称波形。
该研究通过使用TMS电路设计技术以及波形优化，为低能耗、低噪声经颅磁刺激提供了一种方法和新思路。
