IEC 60601-1: EMC problems: Confused about 915MHz ISM band in Europe

B

bustaxica

#1
Just joined the forum today. Have this confusion about 915MHz ISM band in Europe. It is clearly stated in CISPR 11 that 902 to 928MHz is not part of the ISM band in region outside the US.

However, I see many medical systems such as Hyperthermia or Microwave ablation (for prostate, uterus ablation, cancer, etc) in the market using that exact 902-928MHz band in Europe. Did I miss something here?

I can give you an example like the BSD-500 from BSD medical, they use high power (up to 400W) at 915MHz and they got their CE mark.

Also, if it is not part of the ISM band, we just need to show that the emission is lower than the one shown in CISPR11. However, with a high power therapeutic system, it is quite tough to pass that.

Anyone has insight on that? I am working on a project on this and we have to get the CE mark for a 915MHz microwave therapeutic system.

Thanks!
 
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Stijloor

Staff member
Super Moderator
#2
Just joined the forum today. Have this confusion about 915MHz ISM band in Europe. It is clearly stated in CISPR 11 that 902 to 928MHz is not part of the ISM band in region outside the US.

However, I see many medical systems such as Hyperthermia or Microwave ablation (for prostate, uterus ablation, cancer, etc) in the market using that exact 902-928MHz band in Europe. Did I miss something here?

I can give you an example like the BSD-500 from BSD medical, they use high power (up to 400W) at 915MHz and they got their CE mark.

Also, if it is not part of the ISM band, we just need to show that the emission is lower than the one shown in CISPR11. However, with a high power therapeutic system, it is quite tough to pass that.

Anyone has insight on that? I am working on a project on this and we have to get the CE mark for a 915MHz microwave therapeutic system.

Thanks!
Can a Medical Device Expert help?

Thank you very much.

Stijloor.
 

Marcelo

Inactive Registered Visitor
#3
Another bump here. I´m not an expert in EMC and radio frequency, so i cannot help. I´ve made some searches in the net but could not arrive at any conclusion.

Anyway, just as a general comment, CE marking does not mean much regarding a lot of things, which might include frequency bands. Also, CISPR 11 is a standard, and standards are voluntary. I assume there are other regulations on raqdio frequency on the EU, but i can easily see a manufacturer having CE mark and not having followed the regulations..in this case, he might be doing something wrong.

On the other side, this might be a case where there are some options of compliying with the regulations and not being inside the band mentioned.
 
B

bustaxica

#4
Thanks for the insight and comments.

After spending quite some time with the 601 standards it seems like we understand more about all these EMC leakage issues. I think it is worthwhile to share this with the others and see if they have more insight to that.

It seems like there are two standards which are close to the applications we discuss:

1) 60601-2-2: this is the safety requirements for high frequency surgical device

2) 60601-2-6: this is the safety requirements for microwave therapy equipment

Now, the murky thing is that 60601-2-2 is revised constantly. I think the most updated revision is 2009.

In contrast 60601-2-6 has not been revised since 1984. Now, there is no distinction between High frequency or microwave surgical or therapeutic device. The standards for Microwave therapy equipment also excludes hyperthermia device. Now, in 1984, there was no clear distinction between ablation or hyperthermia. The latter just means using energy to increase the tissue temperature. When researchers use higher power, they realize not only you can increase the temperature, if it is high enough, you can create necrosis in the tissue. So, you can "kill" the abnormal tissue if that is what you want. Then it comes the distinction between hyperthemia (lower temperature) and ablation (high temperature)

Now, the dilemma is that many microwave devices can be considered HF surgical devices. Yeah, the frequency is higher, but the results are the same. Also, the def of HF is >200KHz in 60601-2-2. So, there is no clear cut of what is HF or microwave. So, which standards to follow?

You just depend on the mercy of the test house. Unfortunately, it seems like they are as confused as everyone. You basically have to do all the homework and show it to them.

I think the reason is that in the field of using energy to ablate or coagulate human tissues (e.g. treating cancer, bph, etc), "radio frequency" or RF ablation is much more popular than microwave. In pure electrical definition, there is no clear distinction between radio frequency or microwave. But in medical field, microwave is generally referred to higher frequencies (e.g. 915MHz, 2.45GHz). RF means lower frequency (e.g. 500KHz). Now, electrical engineers will laugh at this kind of distinction because these microwave frequencies are just part of RF.

Now, since more companies are using RF (lower) frequency, I think the IEC committee updated the 60601-2-2 standards timely. On the other hand, microwave ablation is less popular and the 60601-2-6 has not been revised since 1984.

So, when we looked at the standard for 60601-2-2, it clearly says in section 36 that yes, the EMC emission will surpass the one is CISPR 11, but since the RF ablation is relied on radition or emission to cure the patient and the POWER on time is very short (i.e. in seconds to minutes), they are exempted from the test when the RF power is ON. They just did the test in standby mode.

Now, I think the same justification is used for microwave frequencies (such as 915MHz): Because it is such a short period of time, and the technology relies on emission to create this therapeutic effects. It should be exempted when the microwave power is ON.

This is the only reasoning behind all these high power devices using 915MHz in Europe.

Imagine you have to design an applicator or an antenna that won't emit energy so that it passes the EMC test. Yes, it passes the EMC test but since it can't emit energy, it can't cure the patient, then what is the point?

People tend to think that you can do the test in saline or liquid phantom. But imagine this, the power you use to ablate is in the levels of tens of even hundred of Watts. The CISPR standard is referring the typical telecommunication which is using mW level at max. This just makes no sense to check the emission when you are ablating.
 
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