MRI - Well that was an experience.....

[fossyant]

Had my MRI on my spine / shoulder last night.

That was an experience. The scanner hole looks quite big....from the outside....but once you are slid into position it's very tight - not much wider than your shoulders, and the top is no more than 3-4 inches off your face.... - fortunately I don't suffer from Claustrophobia !

As you are put into place, there are some low lights inside the scanner - looks a bit like a runway strip....

Well, the flipping noise...sheesh..... and with ear plugs...Had it been a machine with moving parts you'd think it was terminal. The good thing was I'd sat outside going over the 'safety questionnaire' - no metal bits in body, no metal shards in eyes etc..... and I could hear the machine being used on another patient.

It goes something like this... CLICK.... CLICK....CLUNK...CLUNK.............
GRRR..NRRRRR
GRRR..NRRRRR
GRRRR..NRRRR...etc.....
and DDDDD.....DDDDD
......DDDDD.....DDDDD
......DDDDD.....DDDDD

Had six scans in total, two short ones of 30 seconds and 4 3 minute ones... not too bad, but if you are a large person, or don't like confined spaces...argh......

The images are outstanding - I was having a nosey at the patient before me as the images were being processed.

So now you know what it goes like !

 

[Globalti]

Any brain cells found lodged in there?

 

[fossyant]

Ooops - Admin can you fix...the GRRR NRR's have buggered up the formatting - all gone off the page...

Ah I've fixed it now

 

[fossyant]

Any brain cells found lodged in there?

Nah

 

[magnatom]

I'm a MRI physicist so it's always interesting to hear what people make of the experience. Now for todays lecture...


There is one very strong magnet in the scanner that is always on, but to get the pictures out smaller electromagnets need to be switched on and off very, very quickly (and radiofrequency pulses need to applied and detected). Each time these magnets are switched on they vibrate a little, so that is what creates the noise. Did you also notice the tweet, tweet sound as you went into the room? That is the compressor. The compressor helps to keep the liquid helium, liquid. Yes indeedy, you were surrounded by very cold liquid helium which keeps the main magnet very cold and allows it to produce the very strong magnetic field (superconducting magnet which is usually between 30,000 and 60,000 times the earths magnetic field).

The two short scans that you had would have been localisers, i.e. they shows where your body is in the scanner and allow the other scans to be planned. The other scans would have looked at your tissues in slightly different ways (T1 weighted, T2 weighted etc). Each scan can show slightly different things that the radiologist can look at.

Anyway, it looks like times up for this mornings lecture. Next week I will go into more detail about pulse sequences (spin echo, gradient echo, and echo planar imaging), and I will touch on some of the more advanced techniques like angiography, functional MRI and spectroscopy.

Any questions?

(MRI is fun! )

 

[phil_hg_uk]

Yes when can we expect a quieter version out

 

[magnatom]

Funny you should ask, because there is a push at the moment to make them quieter. This is despite the fact that as the technology advances the demands on the scanners are increasing, so without the added sound damping they would be getting much nosier.

Amazing pieces of kit, you know!

 

[magnatom]

Uncle Mort,

Are you sure that wasn't the MRI scanner. Depending on what sequences they run it can really sound like some sort of techno music. Depending on the age of the scanners some are more tube like than others. The newer scanners tend to feel more open.

In fact a conference I went to a number of years ago had a special session where people were invited to set their scanners up to make music etc. They managed to fill a whole session with groups who set their scanner up to play like a piano, play techno music etc.

I should add that none of the groups who were in this session were from the NHS or from the UK!

 

[dan_bo]

I'm a MRI physicist so it's always interesting to hear what people make of the experience. Now for todays lecture...

Any questions?

(MRI is fun! )

Have you ever had a power dump tom and had to evacuate before you suffocate?

 

[magnatom]

Have you ever had a power dump tom and had to evacuate before you suffocate?

Aha, good question. Your talking about a quench!

If the power goes down, the way the scanner is designed the helium can stay cold for a reasonable length of time, but it will start to boil off slowly. There are routes where the helium can escape safely. Usually the scanner can survive reasonably happy like this for a couple of days.

A quench (where the liquid helium suddenly heats up and the superconducting wire gets hot and stops producing the magnetic field) can happen, though they are very rare. In the past it was possible for the helium to blow back into the room, possibly suffocating anyone in it! Don't panic though, there are now measures in place to make sure that can't happen.

I have intentionally quenched a magnet once, that was fun!

 

[magnatom]

They were probably Belgians then!

Funny you should say that, I think one group were!

 

[redjedi]

Have you ever had a patient forget about something metallic they had on/in their body?

If so was it messy?

 

[dan_bo]

Aha, good question. Your talking about a quench!

If the power goes down, the way the scanner is designed the helium can stay cold for a reasonable length of time, but it will start to boil off slowly. There are routes where the helium can escape safely. Usually the scanner can survive reasonably happy like this for a couple of days.

A quench (where the liquid helium suddenly heats up and the superconducting wire gets hot and stops producing the magnetic field) can happen, though they are very rare. In the past it was possible for the helium to blow back into the room, possibly suffocating anyone in it! Don't panic though, there are now measures in place to make sure that can't happen.

I have intentionally quenched a magnet once, that was fun!

Durham Uni had a quench on thier finnegan FT once whilst I was working on one of thier other MS. Chuffing expensive fun that Tom!

 

[magnatom]

Have you ever had a patient forget about something metallic they had on/in their body?

If so was it messy?

Yes. It happens, but no we have only had minor incidents as we have a good safety checklist here and some great staff who enforce it. Complacency is not an option!

It has got messy elsewhere, and there have been deaths. There is a law suit running in the US over a case where a child was killed by someone bringing the wrong type of oxygen cylinder into the MR scanner room.

 

[redjedi]

Yes. It happens, but no we have only had minor incidents as we have a good safety checklist here and some great staff who enforce it. Complacency is not an option!

It has got messy elsewhere, and there have been deaths. There is a law suit running in the US over a case where a child was killed by someone bringing the wrong type of oxygen cylinder into the MR scanner room.

Ahhhh....that's sad, not at all funny like I hoped it would be