MRI causes interference

[dosw]

As I approached a hospital today, GMRS 17 started buzzing loudly, in some pretty distinct sequences. This started about 3/4ths mile from the hospital. I was on my way to an MRI appointment. And when in the machine I quickly realized what I had been hearing on GMRS 17 was the MRI sequences. For anyone who has had one, the sequences are unmistakable and probably unforgettable.

 

I just found it interesting that the interference started so far away from the hospital, and was so reliably attenuated to channel 17. I didn't hear it on 16 or 18. And the sound my radio made was just like what I was hearing inside the apparatus. And it was an intense level of interference.

 

I don't have a question, just reflecting on the situation.

[bd348]

Once saw the room for proton beam radiation therapy.  Foot thick concrete walls and a bank vault style door.  I don't know what an MRI uses but shielding should be part of the design.  Perhaps some contractor cut corners when it was constructed.

[SteveShannon]

It should probably be reported to the MRI department.  If it’s a shielding problem their techs or someone else might be exposed to too much RF.    I don’t know if that’s a concern, but I notice that they go into a separate room instead of staying in the room when I have an MRI.

Here’s an article on the RF shielding that’s supposed to surround an MRI machine:

https://mriquestions.com/why-rf-shielding.html

[SteveShannon]

13 hours ago, WRQW589 said:

As I approached a hospital today, GMRS 17 started buzzing loudly, in some pretty distinct sequences. This started about 3/4ths mile from the hospital. I was on my way to an MRI appointment. And when in the machine I quickly realized what I had been hearing on GMRS 17 was the MRI sequences. For anyone who has had one, the sequences are unmistakable and probably unforgettable.

 

I just found it interesting that the interference started so far away from the hospital, and was so reliably attenuated to channel 17. I didn't hear it on 16 or 18. And the sound my radio made was just like what I was hearing inside the apparatus. And it was an intense level of interference.

 

I don't have a question, just reflecting on the situation.

Another thought.  I wonder if the communication system in the MRI uses an FRS radio on that frequency and you were simply hearing it.

[tweiss3]

7 minutes ago, Sshannon said:

Another thought.  I wonder if the communication system in the MRI uses an FRS radio on that frequency and you were simply hearing it.

No. I know a gentlemen that did the construction of the MRI rooms and the maximum outside RF levels that were allowed inside the room is extremely low. FRS shouldn't be able to be heard through the shell.

[SteveShannon]

45 minutes ago, tweiss3 said:

No. I know a gentlemen that did the construction of the MRI rooms and the maximum outside RF levels that were allowed inside the room is extremely low. FRS shouldn't be able to be heard through the shell.

No RF should be able to be heard through the shell.  According to the article I linked, RF should be shielded to 100 dB, but according to the OP, something recognizable as RFI matching the sound of the MR scanner is being received 3/4 mile away.  Just for curiosity’s sake, can you ask the gentleman if that sounds right?

[tweiss3]

15 minutes ago, Sshannon said:

No RF should be able to be heard through the shell.  According to the article I linked, RF should be shielded to 100 dB, but according to the OP, something recognizable as RFI matching the sound of the MR scanner is being received 3/4 mile away.  Just for curiosity’s sake, can you ask the gentleman if that sounds right?

Emailed, I'll let you know what he says. Hopefully he responds quickly. If not, I'll nudge him on my way home.

 

I wonder if there could be an issue with the transformer feeding the machine.

[SteveShannon]

1 minute ago, tweiss3 said:

Emailed, I'll let you know what he says. Hopefully he responds quickly. If not, I'll nudge him on my way home.

 

I wonder if there could be an issue with the transformer feeding the machine.

Thanks! That’s a thought.

As I recall, maybe incorrectly, the characteristic sound of an MRI is from a compressor used to supercool magnet coils.  I don’t know if the compressor is inside the magnetic shielding or how that all works, but maybe the VFD for the compressor is causing problems.  Anyway you look at it RFI within a hospital could be bad.

[dosw]

I told the staff operating at the time that it caused interference from 3/4ths mile away as I approached. They seemed underwhelmed and dismissed it as "Yep, these are powerful machines."

 

The sound follows the sequence, and is most likely not a cooling compressor, as it pulses and buzzes at various audible frequencies based on the sequence they're running. A compressor wouldn't be so precise; it would be more of a steady drone, not a sharp buzz at various pitches. I suspect it's the rapid cycling of the magnets. But I'm clearly an untrained armchair amateur. 

 

Anyway, the results are in and I'm fine.

[SteveShannon]

7 minutes ago, WRQW589 said:

Anyway, the results are in and I'm fine.

That’s really the important thing! 

[dosw]

43 minutes ago, Sshannon said:

No RF should be able to be heard through the shell.  According to the article I linked, RF should be shielded to 100 dB, but according to the OP, something recognizable as RFI matching the sound of the MR scanner is being received 3/4 mile away.  Just for curiosity’s sake, can you ask the gentleman if that sounds right?

Yes, that's correct.

 

The MRI sequences produce a loud buzzing sound, in pulses, at various audible frequencies. Very sharp; like if you produced a series of staccato clicks at frequencies that produce tones. A little like listening to sound effects on an old Apple ][ computer but amplified loud enough that you have to wear noise cancelling headphones. The sounds are unmistakable. As I approached, from a distance, I thought I was hearing someone transmitting a digital signal on GMRS, and was thinking "How are they getting away with a continual data transmission?" Then as I laid there in the machine, my first time ever having an MRI, hearing that sound, I realized that's what I had been hearing on GMRS/FRS 17.

 

The facility in question is the Park City Intermountain Healthcare hospital.

[dosw]

For those who haven't had the pleasure of laying in one of these for 40 minutes, here's the sound:

 

https://www.youtube.com/watch?v=TIsrOtSSUQY

[SteveShannon]

10 minutes ago, WRQW589 said:

For those who haven't had the pleasure of laying in one of these for 40 minutes, here's the sound:

 

https://www.youtube.com/watch?v=TIsrOtSSUQY

My wife has had maybe 40 of these (MS and they used to track the progress by scanning multiple times, with and without gadolinium enhancement) and I’ve had 3 or 4. I always wonder which of those sounds mean I need to hold my breath.  You can’t hear it very well on that video, but the background sound that sounds like a fetal heartbeat is what I imagined/misunderstood you were hearing on the radio.  

[tweiss3]

From my friend:

The RF room shielding of an MRI is between 90 and 100 db.

For a MRI scanner any RF in the 400 Mhz range  the field strength would
be in the 10 Tesla   range this is way above the frequencys MRI uses 21
to160 Mhz .5 to 4 Tesla (41 Mhz per Tesla).

Don't think it's a MRI Scanner.

 

 

 

 

[WRKC935]

9 hours ago, tweiss3 said:

From my friend:

The RF room shielding of an MRI is between 90 and 100 db.

For a MRI scanner any RF in the 400 Mhz range  the field strength would
be in the 10 Tesla   range this is way above the frequencys MRI uses 21
to160 Mhz .5 to 4 Tesla (41 Mhz per Tesla).

Don't think it's a MRI Scanner.

 

 

 

 

It wouldn't need to be directly on frequency.  Could be a second or quite possibly a third or fourth harmonic (triple or four times the originating frequency)  which would fall in that range. 

It would also explain why it's only being heard at that distance. 

 

 

[WRUX266]

The simple answer is a lazy MRI tech. It's not unusual for a tech to scan a patient with the MRI suite door open. This defeats the purpose of the RF room shielding. If the resulting RF interference isn't causing an issue with anything else within the facility, no one would be the wiser or find keeping the suite door open unusual. 

[kidphc]

As I approached a hospital today, GMRS 17 started buzzing loudly, in some pretty distinct sequences. This started about 3/4ths mile from the hospital. I was on my way to an MRI appointment. And when in the machine I quickly realized what I had been hearing on GMRS 17 was the MRI sequences. For anyone who has had one, the sequences are unmistakable and probably unforgettable.
 
I just found it interesting that the interference started so far away from the hospital, and was so reliably attenuated to channel 17. I didn't hear it on 16 or 18. And the sound my radio made was just like what I was hearing inside the apparatus. And it was an intense level of interference.
 
I don't have a question, just reflecting on the situation.

I have had several head mri's. Couldn't tell you what they sound like. Was wearing ear plugs, still defeaning. When people ask I don't know, like putting you head next to a jet engine with rocks in it?!



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