Study of Electromagnetic Interference with Medical Engineering Equipment

我们研究了在使用电刀的情况下对心电图机（ECG）的电磁干扰（EMI），这是医疗手术室中最近出现的问题，也是日本手术室技术协会的当前问题。本文指出交流线上的噪声和电刀对心电图的辐射噪声可以用频谱分析仪或示波器测量。结果证明，当手术刀正在操作时，在ECG电极线上的宽频率范围内发生EMI。心电图上的电磁干扰被证明是通过心电图电极线感应的。在切割和凝固操作的情况下，ECG电极线上感应的噪声指示特殊的性能曲线。因此，我们提出了一种抑制心电图机上电磁干扰的方法，即在心电图机的电极编码和心电图机发射端之间加一个低通滤波器。我们已经注意到，ECG上的EMI噪声的起源发生在比1kHz低得多的频率中。我们检查了这些物品和特性的电性能曲线，确定为1kHz的截止频率。我们建议增加一个滤波器的电路，它容纳一个钳位电路和一个限制电路。此外，截止频率应在200 Hz至1 kHz的较低频率处给出，因为ECG的物理信号的频谱除DC外甚至低于约30 Hz。因此，它们远小于在相同频率下发生的EMI水平。因此，我们提出了DSP滤波器，它具有实时操作。

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.