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Comment by didntknowya | Hacker News Reader

yeh one of the common injuries around MRI are not the magnetic field affecting your body but the hidden little metal jewelries in people pockets flying around the room. once we had a metal chair get stucked in and had to shut everything down to remove it.

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Projectile hazards get all the attention, but burns are by far the most common injury in MRI, and account for about 60-70% of adverse events.

https://www.auntminnie.com/index.aspx?sec=ser&sub=def&pag=di...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6734033/

> Among the 133 projectile events were 35 reports (26%) involving patient walkers, wheelchairs, stretchers, and chairs, 13 incidents (10%) with gas cylinders, 13 cases (10%) of magnet components exposed during servicing, 10 events (8%) with workmen's tools.

Yeah, but a gas cylinder or a hammer flying across the room is way cooler.

Oh for sure.

When a crisis occurs in the MRI department (a collapse, arrest, drug reaction etc) someone better man the door, or even better, lock it.

Every emergency seemingly has someone helpfully attempt to take something into the magnet. A wheelchair, oxygen cylinder, defibrillator, stethoscope, or most often, scissors.

Somebody told me that they knew of a case where a hospital porter decided to push a gas cyclinder through the MRI room while the machine was on (shortcut?). The gas cyclinder went through a wall.

It says at: https://www.hospitalmanagement.net/features/feature51496/

"Gas cylinders are a particular risk in the MRI environment. Such cylinders can weigh from 30lb to 150lb when full. Ferromagnetic gas cylinders are especially dangerous in a magnetic environment, where they can be uncontrollably accelerated. Potential hazards include gas-propulsive missile impaction, explosion and fire. If the cylinder regulator valve is damaged on initial impact, the cylinder may propel away from the magnet, only to return for a second impact."

> Somebody told me that they knew of a case where a hospital porter decided to push a gas cyclinder through the MRI room while the machine was on (shortcut?).

The trap is that they are pretty much never ‘off’, they are magnetic when not scanning.

This issue may be reduced with technology such as the Philips Blue Seal thing where you can remove (reduce?) the field at the flick of a switch. However things like this where the danger goes from being ‘always’ to ‘sometimes’ can actually increase accidents. It’ll be an interesting space to watch.

https://www.medgadget.com/2018/09/philips-helium-free-mri-sy...

I assumed it was an electromagnet. Do MRIs all have permanent magnets?

Most are superconducting electromagnets, so.. sort of? They have shipped full of liquid helium then get ramped up (or at least, this is how Siemens do it). With any luck they stay up for many years.

Yeah, undetected metal can certainly be an issue.

I was with my wife in the MRI room, when it was done I handed her her shoes--and felt the magnet pulling on them. I have no idea how there was metal in there, she specifically picked them because they were soft at all points. The pull wasn't strong (had I let go they would have gone to the floor, not to the magnet) but it definitely was there.

From that second article it sounds like manufacturers should be required to put on the label whether a garment was MRI safe or not.

All patients/volunteers going into the scanner should change into a gown and remove their shoes. Places that don’t do this have a vastly greater accident rate in my experience.

It’s surprising what is conductive or magnetic. Many garments now include silver or other anti-microbial materials. I’ve encountered clothing with electronics inside or with metal in the labelling.

Burns are the most common accident in MRI and in someone sedated or under anaesthesia you will cause massive harm. It’s all scary, so I change everyone.

‘MRI safe’ is a risky claim to make, as something safe on one scanner is unsafe on another.

Do you still have to quench the magnet to shut it down? I read back in the day, older magnets could suffer irreversible damage so it would often total the whole machine.

>we had a metal chair get stucked in

You mean like this? https://youtu.be/6BBx8BwLhqg

In an experimental setting, I was once given a screwdriver to feel the field around an MRI machine. They asked me to be very careful of course, because loosing the grip would indded have ment the machine would need to be shut down...

I have a meteorite wedding band and we were passing it around outside the bore to feel how strong the pull was. A grad student lost their grip and the ring shot into the bore like a bullet. No damage luckily but it really drove home how dangerous these can be.

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