That makes sense: so the alignment doesn't shift as the gradient coils operate and heat up, right? Those aren't the superconducting coils, they have Ohmic heating.
Body and gradient coils I believe. They get a lot of current through them. 3x 200 amps at 2000 volts if I recall correctly. They have cooling pipes too.
If a cable wiggles loose it’s a big deal with that much power in use, they start to smoke. Running that that current is a large force on any connections.
Having had quite a few MRIs, the idea of being stuck in the MRI machine and it starting to smoke is quite terrifying.
For people who haven't had the experience, generally getting an MRI involves being stuck in a narrow tube (I'm just under 6'5" so with the proportions of my shoulders I literally just fit in) inside the machine for a long time. Everyone else leaves the room and goes into a nearby operating room and communicates with you over a headset. So if the machine was to catch fire you would literally be trapped inside it and unable to move, which is a really horrific thought.
Any excessive heat would usually be at the gradient connection points in the faraday cage, the gradient cabinets (different room) or edge of scanner. Not a lot better, but fractionally so.
We get Vesda [1] alerts when the air pressure changes or when combustion products are detected. It’s ludicrous how sensitive a Vesda is, you won’t get burnt. If you open to door aggressively you can trigger an alert.
New scanners are now mostly 70cm diameter and some are 80cm. They can be quite relaxing. I recommend a large lunch and being scanned while paid for your time.
I honestly always fall asleep inside them[1] in spite of the fact that the noise is very loud even with the cans on. I'm not sure why I find the experience so relaxing.
[1] Has happened about 5 out of about 6 MRI scans so not "always" but very often.
