Item — HN Reader

> most MRI scanner magnets cannot be turned off like that. For the few that can, it's going to cost >$50,000 just to refill the liquid helium, not to mention the real and opportunity costs associated with rendering the machine offline for days or weeks.

I thought these days, most MRIs did have an emergency quench button.

2 comments

Yeah I would say all modern MRIs do. However one misconception is that loss of field strength is instantanous, it's not. The field strength drops off over about 15s or so as the helium boils off and the magnet losses superconducting properties.

So the emergency quench is less useful than it sounds in these situations... it's very likely if an MRI is going to kill you it's going to do it fast enough for it not to be relevant.

Surely you'd hit the quench button straight away? I cannot imagine policy being "check if the victim is dead, and if not hit the button."

I also wonder what the field decay is like. If it takes 15s and it's linear it's much worse than if it's 15s but decays exponentially. You don't need to field to be gone, you need the field to diminish enough to stop strangling the poor guy.

In this case, he died after being removed from the machine and taken to a hospital.

The damage was likely done almost immediately; a heavy 20 pound "necklace" is going to apply a lot of crushing force.

And for the other readers: It wouldn’t be applying twenty pounds of force, it would be applying…

My rule of thumb calculation came to 3,000 lbf, which seems like a lot, but perhaps that’s actually accurate.

Seems spot on to me.

Figure half that to start since most of the loop is gonna wind up laying flat and only the half of it is prevented from doing so by one's neck. Then maybe cut it by 2/3 again since the sides aren't gonna do a ton of direct squishing. That still leaves you with hundreds of pounds, which roughly aligns with the timeline of suffocation in the article High hundreds low thousand likely would be neck snapping or otherwise instantly incapacitating.

Damage was mostly done at wall impact after distance-square acceleration, not just the slamming against the wall but 1.2 Tera-gauss force inches away from superconducting magnet coil applied at least 3,200 lbs/ft forces on the 20lb gold chain crushing nearly everything on the poor victim's neck, artery, veins, tendons, muscle ... beyond any possible surgical repair.

Apparently he was lucid and speaking for some time before he passed out.

Good for 15 seconds ... after releasing your futile grip to free yourself by the virtue of circulation to the brain.

> The damage was likely done almost immediately;

Not disagreeing, just saying the tech running the machine couldn't have known that and should have quenched the machine in case the damage was survivable.

Right. You - a person who wasn't there, has had no training, has seen no photos and doesn't understand any of the details of the circumstance - are certainly better positioned to know that than the trained staff who were present.

The article says 1hr before it was turned off. That’s long enough to start questioning.

Magnet is ALWAYS ON, 24/7.

Until that big red emergency button gets pressed to the tune of $25,000 to $50,000 each time (couple that with 1-2 weeks downtime and a messed up scheduled for 1,000 of patients.

The person I was replying to wasn't asking questions. He specifically said the operator "should have" quenched the machine. He's just another comment section expert.

You're in luck. Video of an MRI magnet being quenched that I posted above:

https://www.youtube.com/watch?v=9SOUJP5dFEg

Yeah so this video shows exactly what I am talking about, the chair and other objects don't fall immediately, it takes ~15s for them to drop to the ground after the quench starts.

Takes more than 15sec to strangle someone. 30 shouldn't cause any serious damage beyond whatever mechanical damage there is from being tugged around. Heck, 2-3min is probably fine if the MRI is located at a hospital.

Edit: Per the article that I would like to remind everyone is well worth reading, he had time to say goodbye to his wife, that would seem to me to imply he wasn't tossed hard enough to be incapacitated.

strangle? dude's neck was probably crushed. if I had to guess this was a near decapitation, not a strangling.

honestly, probably, yeah, but the guy running the MRI can't know that and should have quenched immediately. You don't just go "oh well he's probably dead, nothing I can do about it now."

my point is even if he had quenched ASAP the damage might've been done already.

Causing severe head trauma or crushing the trachea can be almost instant. A lot of the more serious MRI related injuries are objects flying across the room and hitting someone, especially over the head.

With 3,200 lb/ft forces inches away from 1.2 tera-gauss magnet, all damages were already done to artery, veins, tendons, muscle, by the 20 lbs necklace, all beyond surgical repair.

Per the article, his wife claims that he had time to wave goodbye to her.

A man getting dragged by the neck and hitting an MRI machine head-first is going to make all sorts of hand movements that his grieving widow might interpret as waving goodbye in hindsight.

At distance-sqaured law, he literally accelerated beyond 16 G-force (gravity) and slammed against the machine surface.

After GE got their shit together, yes. https://www.diagnosticimaging.com/view/everything-you-need-k...