U.S. Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993, USA.
Biomed Eng Online. 2011 Oct 21;10:94. doi: 10.1186/1475-925X-10-94.
Over the last decade, the number of neurostimulator systems implanted in patients has been rapidly growing. Nearly 50, 000 neurostimulators are implanted worldwide annually. The most common type of implantable neurostimulators is indicated for pain relief. At the same time, commercial use of other electromagnetic technologies is expanding, making electromagnetic interference (EMI) of neurostimulator function an issue of concern. Typically reported sources of neurostimulator EMI include security systems, metal detectors and wireless equipment. When near such sources, patients with implanted neurostimulators have reported adverse events such as shock, pain, and increased stimulation. In recent in vitro studies, radio frequency identification (RFID) technology has been shown to inhibit the stimulation pulse of an implantable neurostimulator system during low frequency exposure at close distances. This could potentially be due to induced electrical currents inside the implantable neurostimulator leads that are caused by magnetic field coupling from the low frequency identification system.
To systematically address the concerns posed by EMI, we developed a test platform to assess the interference from coupled magnetic fields on implantable neurostimulator systems. To measure interference, we recorded the output of one implantable neurostimulator, programmed for best therapy threshold settings, when in close proximity to an operating low frequency RFID emitter. The output contained electrical potentials from the neurostimulator system and those induced by EMI from the RFID emitter. We also recorded the output of the same neurostimulator system programmed for best therapy threshold settings without RFID interference. Using the Spatially Extended Nonlinear Node (SENN) model, we compared threshold factors of spinal cord fiber excitation for both recorded outputs.
The electric current induced by low frequency RFID emitter was not significant to have a noticeable effect on electrical stimulation.
We demonstrated a method for analyzing effects of coupled magnetic field interference on implantable neurostimulator system and its electrodes which could be used by device manufacturers during the design and testing phases of the development process.
在过去的十年中，植入患者体内的神经刺激器系统数量迅速增长。全球每年植入近 5 万个神经刺激器。最常见的植入式神经刺激器用于缓解疼痛。与此同时，其他电磁技术的商业用途正在扩大，使得神经刺激器功能的电磁干扰（EMI）成为一个令人关注的问题。通常报告的神经刺激器 EMI 源包括安全系统、金属探测器和无线设备。当接近这些源时，植入神经刺激器的患者报告了不良事件，如电击、疼痛和刺激增加。在最近的体外研究中，射频识别（RFID）技术已被证明在近距离低频暴露时会抑制植入式神经刺激器系统的刺激脉冲。这可能是由于植入式神经刺激器引线内部感应电流引起的，这些电流是由低频识别系统的磁场耦合引起的。
为了系统地解决 EMI 带来的问题，我们开发了一个测试平台来评估耦合磁场对植入式神经刺激器系统的干扰。为了测量干扰，我们记录了一个处于最佳治疗阈值设置的植入式神经刺激器的输出，当它接近运行中的低频 RFID 发射器时。输出包含来自神经刺激器系统的电势能和来自 RFID 发射器的 EMI 感应电势能。我们还记录了在没有 RFID 干扰的情况下，处于最佳治疗阈值设置的相同神经刺激器系统的输出。使用 Spatially Extended Nonlinear Node (SENN) 模型，我们比较了两个记录输出的脊髓纤维激发的阈值因素。
低频 RFID 发射器感应的电流没有明显的影响，不会对电刺激产生明显的影响。
我们展示了一种分析耦合磁场干扰对植入式神经刺激器系统及其电极影响的方法，设备制造商可以在开发过程的设计和测试阶段使用该方法。
