Xu Qi, Li Xinru, Lu Zhixin, Wu Yongchao
School of Artificial Intelligence and Automation, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.
Department of Rehabilitation, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, P. R. China.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2025 Apr 25;42(2):300-307. doi: 10.7507/1001-5515.202407004.
Clinical trials have demonstrated that kilohertz-frequency transcutaneous spinal cord stimulation (TSCS) can be used to facilitate the recovery of sensory-motor function for patients with spinal cord injury, whereas the neural mechanism of TSCS is still undetermined so that the choice of stimulation parameters is largely dependent on the clinical experience. In this paper, a finite element model of transcutaneous spinal cord stimulation was used to calculate the electric field distribution of human spinal cord segments T to L , whereas the activation thresholds of spinal fibers were determined by using a double-cable neuron model. Then the variation of activation thresholds was obtained by varying the carrier waveform, the interphase delay, the modulating frequency, and the modulating pulse width. Compared with the sinusoidal carrier, the usage of square carrier could significantly reduce the activation threshold of dorsal root (DR) fibers. Moreover, the variation of activation thresholds was no more than 1 V due to the varied modulating frequency and decreases with the increased modulating pulse width. For a square carrier at 10 kHz modulated by rectangular pulse with the frequency of 50 Hz and the pulse width of 1 ms, the lowest activation thresholds of DR fibers and dorsal column fibers were 27.6 V and 55.8 V, respectively. An interphase delay of 5 μs was able to reduce the activation thresholds of the DR fibers to 20.1 V. The simulation results can lay a theoretical foundation on the selection of TSCS parameters in clinical trials.
临床试验表明，千赫兹频率经皮脊髓刺激（TSCS）可用于促进脊髓损伤患者感觉运动功能的恢复，然而TSCS的神经机制仍未明确，因此刺激参数的选择在很大程度上依赖于临床经验。本文利用经皮脊髓刺激的有限元模型计算人体T至L脊髓节段的电场分布，同时采用双电缆神经元模型确定脊髓纤维的激活阈值。然后通过改变载波波形、相间延迟、调制频率和调制脉冲宽度来获得激活阈值的变化。与正弦载波相比，使用方波载波可显著降低背根（DR）纤维的激活阈值。此外，由于调制频率的变化，激活阈值的变化不超过1 V，且随调制脉冲宽度的增加而降低。对于由频率为50 Hz、脉冲宽度为1 ms的矩形脉冲调制的10 kHz方波载波，DR纤维和背柱纤维的最低激活阈值分别为27.6 V和55.8 V。5 μs的相间延迟能够将DR纤维的激活阈值降低至20.1 V。仿真结果可为临床试验中TSCS参数的选择奠定理论基础。
