College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu 610059, China.
High Field Magnetic Resonance Brain Imaging Laboratory of Sichuan, Chengdu 611731, China.
Sensors (Basel). 2024 Jun 13;24(12):3839. doi: 10.3390/s24123839.
As a noninvasive neuromodulation technique, transcranial magnetic stimulation (TMS) has important applications both in the exploration of mental disorder causes and the treatment of mental disorders. During the stimulation, the TMS system generates the intracranial time-varying induced E-field (E-field), which alters the membrane potential of neurons and subsequently exerts neural regulatory effects. The temporal waveform of the induced E-fields is directly related to the stimulation effect. To meet the needs of scientific research on diversified stimulation waveforms and flexible adjustable stimulation parameters, a novel efficient pulse magnetic stimulation circuit (the EPMS circuit) design based on asymmetric cascaded multilevel technology is proposed in this paper. Based on the transient analysis of the discharge circuit, this circuit makes it possible to convert the physical quantity (the intracranial induced E-field) that needs to be measured after magnetic stimulation into easily analyzable electrical signals (the discharge voltage at both ends of the stimulation coil in the TMS circuit). This EPMS circuit can not only realize monophasic and biphasic cosine-shaped intracranial induced E-fields, which are widely used in the market, but also realize three types of new intracranial induced E-field stimulation waveform with optional amplitude and adjustable pulse width, including monophasic near-rectangular, biphasic near-rectangular and monophasic/biphasic ladder-shaped stimulation waveform, which breaks through the limitation of the stimulation waveform of traditional TMS systems. Among the new waveforms produced by the EPMS circuit, further research was conducted on the dynamic response characteristics of neurons under the stimulation of the biphasic four-level waveform (the BFL waveform) with controllable parameters. The relationship between TMS circuit parameters (discharge voltage level and duration) and corresponding neural response characteristics (neuron membrane potential change and neuronal polarizability ratio) was explained from a microscopic perspective. Accordingly, the biological physical quantities (neuronal membrane potential) that are difficult to measure can be transformed into easily analyzable electrical signals (the discharge voltage level and duration). Results showed that compared with monophasic and biphasic cosine induced E-fields with the same energy loss, the neuron polarization ratio is decreased by 54.5% and 87.5%, respectively, under the stimulation of BFL waveform, which could effectively enhance the neuromodulation effect and improve the stimulation selectivity.
作为一种非侵入性神经调控技术,经颅磁刺激(TMS)在探索精神障碍病因和治疗精神障碍方面具有重要应用。在刺激过程中,TMS 系统会产生颅内时变感应电场(E 场),该电场会改变神经元的膜电位,进而发挥神经调节作用。感应 E 场的时间波形直接关系到刺激效果。为满足对多样化刺激波形和灵活可调刺激参数的科学研究需求,本文提出了一种基于非对称级联多电平技术的新型高效脉冲磁刺激电路(EPMS 电路)设计。基于放电电路的瞬态分析,该电路将磁刺激后需要测量的物理量(颅内感应 E 场)转换为易于分析的电信号(TMS 电路中刺激线圈两端的放电电压)。这种 EPMS 电路不仅可以实现市场上广泛应用的单相和双相余弦形颅内感应 E 场,还可以实现三种具有可选幅度和可调脉冲宽度的新型颅内感应 E 场刺激波形,包括单相近矩形、双相近矩形和单相/双相梯级形刺激波形,突破了传统 TMS 系统刺激波形的限制。在 EPMS 电路产生的新波形中,进一步研究了具有可控参数的双相四电平波形(BFL 波形)刺激下神经元的动态响应特性。从微观角度解释了 TMS 电路参数(放电电压电平与持续时间)与相应的神经响应特性(神经元膜电位变化与神经元极化比)之间的关系。因此,将难以测量的生物物理量(神经元膜电位)转化为易于分析的电信号(放电电压电平与持续时间)。结果表明,与具有相同能量损耗的单相和双相余弦感应 E 场相比,BFL 波形刺激下神经元的极化比分别降低了 54.5%和 87.5%,可有效增强神经调控效果,提高刺激选择性。