Study of Electromagnetic Interference with Medical Engineering Equipment

我们研究了在使用电手术刀的情况下，心电图（ECG）的电磁干扰（EMI），这是最近在医疗手术室出现的问题，也是日本手术室技术协会的当前课题。指出交流线路上产生的噪声和电刀对心电的辐射噪声可以用频谱分析仪或示波器测量。结果证明，在电刀操作过程中，电磁干扰会在较宽的频率范围内发生在ECG电极上。心电上的电磁干扰是通过心电电极引起的。在切割和凝血两种情况下，对心电电极绳产生的噪声表现出一种特殊的性能曲线。因此，我们提出了一种抑制心电干扰的方法。它是在心电电极码和心电发送器之间加一个低通滤波器。我们已经注意到，在ECG上的EMI噪声的起源发生在一个远低于1kHz的频率。我们检查了这些文章，并确定了截止频率为1kHz的电性能曲线的特性。我们建议增加一个滤波器电路，它可以容纳一个箝位电路和一个限流电路。此外，截止频率应在200Hz至1kHz的较低频率范围内给出，因为心电物理信号的频谱除直流外甚至低于30Hz左右。因此，它们比在相同频率下发生的电磁干扰水平小得多。为此，我们提出了具有实时性的DSP滤波器。

We had studied the Electromagnetic Interference (EMI) with the electrocardiograph (ECG) in case of using an electric scalpel, which is a recent problem in medical operation rooms and is a current issue Japanese Association for Operating Room Technology. We pointed out that the noise induced on the AC-line and the noise radiated from an electric scalpel to ECG can be measured by spectrum analyzer or oscilloscope. As a result, it proved that EMI occurs in a wide frequency range on the ECG electrode cord while an electric scalpel is being operated. And EMI on the ECG proved to be induced through the ECG electrode cord. The noise induced on the ECG electrode cord indicates a special performance curve in case of operation both for cutting and for coagulation. Therefore, we made a proposal for the way of suppressing EMI on the ECG.It is that a low-pass filter is added between the ECG electrode code and the ECG transmitter. We have noticed that the origin of EMI's noise on the ECG occurs in a much lower frequency than 1kHz. We inspected these articles and the characteristic- of electric performance curves which were determined to 1kHz for the cut-off frequency. We suggest an added filter's circuit which accommodates a clamp circuit and a limited circuit. Furthermore, the cut-off frequency should be given at the lower frequency from 200Hz through 1kHz, because the spectrum of physical signals of ECG is even lower than about 30Hz except DC.Therefore, they are much smaller than EMI level occurring at the same frequency. As a result, we proposed DSP filter, which has the real-time operation.