MRI Question (Pulling Feeling)

Satur9 · April 21, 2020, 5:57pm

TIL that a 16 Tesla magnetic field can cause small animals and plants to paramagnetically levitate

SammichBrad · April 21, 2020, 5:58pm

That’s pretty neat… and weird… but most neat haha.

NiamhAstra · April 21, 2020, 6:23pm

Apparently human scanners go to 10.5 Tesla

amal · April 22, 2020, 1:35am

Both. It’s impossible to predict how a magnet will interact with an MRI field, and there are many different MRI designs which produce different shaped fields and work somewhat differently as well. Anecdotal evidence suggests that very small magnets (m31) could be “held” in place with external force, but even slightly larger ones caused so much pain trying to move and exit tissue that they had to abort the MRI scan. Of course these stories come from people who hid the fact they had magnet implants from MRI technicians, and of course these stories cannot be confirmed… so we really suggest that this not be something our customers experiment with… if you’re going in for an MRI, have your magnets removed before the procedure.

Most hospitals use 1.5T to 3T machines… labs and universities doing medical imaging studies can get up to 7T.

Pilgrimsmaster · April 22, 2020, 1:44am

Luckily in this case, @David86 only has an xNT

anon3825968 · April 22, 2020, 2:19am

Ah yes, I didn’t think about the pain.

So for smaller magnets, it comes down to pain of removal and replanting vs pain of MRI scanner trying to rip out the magnet.

I wonder if those machines have a “test mode” - as in, provided the technician is sympathetic, you could perhaps walk up to them and ask them to slowly “turn up the volume” and see if it gets too unpleasant before reaching the level needed for the exam proper.

Backpackingvet · April 22, 2020, 2:23am

I work very limited with MRI machines at work. They are always “on” so I am not sure how close you should even get to it with a magnet. The test would just be walking towards it.

NiamhAstra · April 22, 2020, 2:34am

Yes MRIs are “always on” usually. They use super conductors for most MRIs (I think some use permanent magnets) and require “quenching” to turn them off. This can damage the machine and costs a lot of coolant (liquid helium usually).

Stumbled across this earlier and it seemed interesting:

ncbi.nlm.nih.gov

MRI induced torque and demagnetization in retention magnets for a bone conduction implant.

KJ Jansson, B Håkansson, S Reinfeldt, H Taghavi and M Eeg-Olofsson, IEEE transactions on bio-medical engineering, Jun 2014

Performing magnetic resonance imaging (MRI) examinations in patients who use implantable medical devices involve safety risks both for the patient and the implant. Hearing implants often use two permanent magnets, one implanted and one external, for the retention of the external transmitter coil to the implanted receiver coil to achieve an optimal signal transmission. The implanted magnet is subjected to both demagnetization and torque, magnetically induced by the MRI scanner. In this paper, demagnetization and a comparison between measured and simulated induced torque is studied for the retention magnet used in a bone conduction implant (BCI) system. The torque was measured and simulated in a uniform static magnetic field of 1.5 T. The magnetic field was generated by a dipole electromagnet and permanent magnets with two different types of coercive fields were tested. Demagnetization and maximum torque for the high coercive field magnets was 7.7% ± 2.5% and 0.20 ± 0.01 Nm, respectively and 71.4% ± 19.1% and 0.18 ± 0.01 Nm for the low coercive field magnets, respectively. The simulated maximum torque was 0.34 Nm, deviating from the measured torque in terms of amplitude, mainly related to an insufficient magnet model. The BCI implant with high coercive field magnets is believed to be magnetic resonance (MR) conditional up to 1.5 T if a compression band is used around the skull to fix the implant. This is not approved and requires further investigations, and if removal of the implant is needed, the surgical operation is expected to be simple.

NiamhAstra · April 22, 2020, 2:38am

Here is a video of a MRI being quenched if it interests anyone:

anon3825968 · April 22, 2020, 2:43am

Interesting. I didn’t know them machines were on all the time.

I very much hope that plume of white smoke in the video wasn’t helium being vented out. That would be shameful, considering the world will soon run out of the stuff.

NiamhAstra · April 22, 2020, 2:48am

That is exactly what it is (afaik), as I said it wastes a lot of coolant.

I believe it is only intended to be an emergency or end of life event and given machines like that are old I doubt the recycling of the coolant was even considered.

Backpackingvet · April 22, 2020, 2:55am

Very much so. Also need to clear people out in case it doesn’t vent correctly.

anon2520759 · April 22, 2020, 3:04am

This was really cool to watch and learn about, thanks!

amal · April 22, 2020, 4:17am

Yeah but death by helium would sound hilarious.

NiamhAstra · April 22, 2020, 4:18am

Go out on a high note? so to speak?

Backpackingvet · April 22, 2020, 2:01pm

Or we could unintentionally become super human, just like no good, lazy pos, grandpa Joe.

part-2

Satur9 · April 22, 2020, 3:01pm

I don’t always laugh for three minutes, but when I do it’s because that was fucking funny.

David86 · April 26, 2020, 5:26am

Hey All,
So I wanted to update everyone on my MRI.

so I ended up having an MRI on friday after I sent the MRI PDF from Dangerousthings.com and also the link to the testing page.
I spoke with the Technician before I had the scan about it and they said it will be fine.

so I stuck my hand in the machine same as I did on monday and had no effect this time (clearly it was all in my head) My scan went for 30 mins and to say I didn’t enjoy myself would be an understatement.

I was sure I felt my chip move and buzz while I was in the scanner, but my whole body also buzzed while in it.

What I can say is moving forward I won’t worry about having a scan done again.

Also if anyone was wondering, the scan I had was a 1.5 Tesla, it was loud and not fun. After the scan where the chip is in my hand felt warm and itchy to me, to my partner it was cold, so clearly it was all in my head. 2 days later and its fine with no issue at all.

Also my chip still works fine I tested it as soon as I got home.

Thanks to everyone that responded and thanks for all the links and info.

Thanks David

Edit: added Links