> "I'm saying, 'Could you turn off the machine? Call 911. Do something. Turn this damn thing off!'" [pleaded the victim's wife].
The journalist missed a golden opportunity for education here: 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.
If people don't know about the magnet, or don't know that it can't be turned off (or perhaps assume it's "off" because the scan was over, as I would guess happened here), accidents happen.
If anyone is curious what pushing the button to turn off (AKA "quench) the magnet looks like, there's this video of an MRI machine being decommissioned:
You push the button, then 15 seconds later the liquid helium is vented through a pipe on the roof of the hospital (it's quite a spectacular display), and then the superconductor starts to heat up and no longer be a superconductor so the current that's been flowing through the coils (they are energized once, when the machine is first installed, and then continue flowing forever so long as the superconductor is superconducting since there's no resistance) and the magnetic field decays to nothing.
I’m pretty sure when some guy gets sucked into the machine, the downtimes/lawsuits/etc and pressing the emergency button and having a ton of down time is a sunk cost at that point and you are basically obligated to do everytyhing you can to avoid catastrophe to reduce your legal peril.
There’s also the basic idea that a human life is worth saving. The money can be figured out later. Sadly though the magnetic fields of an MRI don’t disappear by simply powering the machine down. It can take a while even then. The fact a man with an enormous iron chain is allowed to walk into the room under any circumstance is where the lawsuits will come from, and rightly so.
Quenching the magnet takes up to several minutes. There are also alarms to warn people to get away because the rapidly expanding helium could displace oxygen in the room.
It’s not about the cost. If there’s an emergency that necessitates pressing the button they’ll be pressing it as soon as someone can reach it. It still takes time for the magnetic field to dissipate.
Not a physist, but I remember from school when studying electrical resonators, the stronger the inductor the lower the resonant frequency. i.e. the stronger the magnetic field the longer it takes to turn back into current.
I would guess a strong magnet takes a while, probably minutes to shed its field.
Saturation/critical current: zero resistance doesn't mean infinite current. all superconductors gain resistance if the current exceeds a value. This value is temperature dependent.(http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/scbc.html).
In the idealized resonator, the impedance is assumed zero what matters is the inductor strength and the capacity in the capacitor.
In a real MRI, I presume there is no capacitor to take the charge, I am guessing the limiting factor is the impedance of wherever the charge is going to go.
> 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.
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.
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.
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.
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 don't have to voice your opinion just because you have one, if you're an expert people might want to hear what you have to say but otherwise you're just padding the comments with slop.
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.
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."
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.
> The journalist missed a golden opportunity for education here: most MRI scanner magnets cannot be turned off like that.
Thanks for that - and it reminded me of the sad state media is today. I read the same story in about 4 papers and nowhere was written _why_ they couldn't turn off the machine.
Miss the days where journalists actually read what they have written.
They can be quenched (as you note), but there was that one time that GE didn’t connect the quench button to prevent accidental/expensive usage and n India, and someone died.
Surprise! It turns out there is a reason it should be connected.
MRI techs do not think about it cost when life is at danger. If someone is in life danger due to the magnet, you quench. This is standard MRI education.
I think the big question here is why they didn’t..
That's a huge deal. I read the article and assumed the machine was mistakenly thought to be turned off or was "winding down". That's especially frustrating as the patient seems to be blaming the hospital staff for the incident.
The patient would be 100% correct to blame the hospital staff for this incident. The only possible explanation is human error by the staff. The only reason this doesn't happen every day in hospitals around the world is MRI staff are not incompetent.
In the US the federal government uses numbers around $10 million for the statistical value of a human life when doing cost benefit analysis for various programs or interventions. Any sort of lifesaving medical care can easily come in at more than $50,000. The operators shouldn't be hesitating to shut down that machine to save someone's life, and I would be willing to be that they are trained to do so.
Now you are at the Trolley problem: shut down the machine to (maybe) save one person, but preventing all MRIs for the next x weeks, causing y indirect deaths?
The Trolley problem is only a problem because there is perfect information in the hypothetical about the consequences of your actions. In real life, you have far less information to go on, which often leads to a more obvious right answer. Shutting down the machine to try to save the one person right in front of you that you know is in immediate danger is the right answer, versus the far less knowable hypothetical future where some number of people may or may not have delayed or relocated scans which may or may not have delayed treatment that may or may not have been immediately necessary as a life-saving matter. As a private MRI operator, you are not morally responsible for keeping your machine functional in order to help keep (figurative) passers-by alive. But you are morally responsible for the health and safety of the patients and visitors on your premises.
It'll need to be shut down anyway to pull the giant metal chain out. You might as well do it right away. Patients can and will be rescheduled to other MRI facilities.
> 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,
I now nothing about MDI so please tell me: why does it need to refuel the helium? Aren't the magnets “just” superconductive electromagnets? Why can't the current powering the magnet be stopped?
Edit: thanks everyone for your explanations, I appreciate it.
They require extremely low cooling from the helium to achieve superconductivity.
And with superconductivity, by definition, current flows without resistance; it continues even without energy, so turning off the power won't stop it. Nor will it heat up and decay from resistance. Modern MRIs are well-insulated enough to maintain their field without power from days to weeks.
The only thing that collapses the field is to warm it up to where superconductivity stops, which can be done slow and expensively, or in an emergency, fast and even more expensively.
By venting the supercooled gases in what's called a quench, you can turn it off faster, but the time it needs can depend on the model. It could be 20 seconds, or it could be 2 minutes, which, depending on the emergency, may be insufficient.
A quench itself can be dangerous, though usually less so than a patient pinned to the magnet. There's a chance that poor ventilation can flood the room with helium, causing loss of consciousness in seconds. The increase in pressure can also make it impossible to escape if the door's not built for that. You'd have to break a window. On top of which, it's dangerously cold, and the explosive bang can rupture your eardrums.
You actually don't need to actively supply current -- it just keeps going round and round, and you can't "short" it out because the path of least resistance will always be the superconducting winding.
You also can't open a switch to stop the current because it's basically a giant inductor, it really wants to keep the magnetic field (and current) constant. Meaning if you suddenly disconnected the winding, it would arc across the gap (continuously, for quite a while until the stored energy was spent).
So what they do is vent/boil off the liquid helium which is keeping the magnet cold, such that it's no longer superconducting and the current will die off. You can't reclaim the helium, hence you need a fresh refill to chill down the magnet again.
"Any change to the current through the magnet must be done very slowly, first because electrically the magnet is a large inductor and an abrupt current change will result in a large voltage spike across the windings, and more importantly because fast changes in current can cause eddy currents and mechanical stresses in the windings that can precipitate a quench [...]. So the power supply is usually microprocessor-controlled, programmed to accomplish current changes gradually, in gentle ramps. It usually takes several minutes to energize or de-energize a laboratory-sized magnet."
For what it’s worth I just learned this from chatgpt. But the magnet is a superconducting electromagnet, and it’s started up by cooling the superconducter to around 4 Kelvin, and then electricity is turned on, and then once it’s going at the desired current, there is some kind of superconducting switch that disconnects the power source. After that no more power is supplied to the magnet—it will run with that same current for years, as long as you keep it cold enough to be super conducting. Apparently the resistance is actually truly zero, not just almost zero.
So there is no current to turn off. The current in the magnet is running on its own from when it was first supplied. The only way to stop it is to heat up the superconductor.
I thought maybe you could draw it off and use it up somewhere else, but then if I’m remembering right electricity will always take the last of least resistance, so none of it would leave a superconductor. Right?
It also makes me wonder, if someone is ever able to build a warm superconductor, how would we ever stop electricity we’ve put into a system like that?
I wrote 100% of my post myself. There’s no bragging going on. I’m warning people that I learned it from chatgpt so they know it may not be trustworthy. Still in my experience the vast majority of what I learn from ChatGPT/gemini/claude is correct, and in this kind of case where the knowledge is interesting but not something I’m going to need to rely on for anything, the benefits of quickly learning are so high for me that I thought someone else might appreciate it too. I’m sorry if I offended you.
> the vast majority of what I learn from ChatGPT/gemini/claude is correct
Roughly 90% according to benchmarks. Which means you're learning 10% bullshit.
> the benefits of quickly learning are so high for me that I thought someone else might appreciate it too
ChatGPT has been there for two and a half years already, of course everyone on this forum knows about it, you don't have to tell people how cool it is… Rather you can safely assume that if someone asks a question here, and not as a ChatGPT prompt, it means they doesn't want an answer from ChatGPT!
I didn’t give you an answer from chatgpt. I’m not telling anyone how cool it is. I’ve been here for years and I’m well aware of the level of exposure to LLMs there is for people on HN .
I did give out a warning to people that I had learned something from chatgpt, not from some other source, so they could take it for what it was worth.
I’m so tired of seeing people in other forums try to help someone and having someone give them a shit response. One thing I like about HN is the fact that that doesn’t happen much here. I still think what I wrote in response to your question was helpful and thoughtful. Back up a minute and just think it over, please.
I’d love to see which benchmarks you’re talking about, and if they apply to all three of those specific LLMs, and which version of their models, and if they differentiate topics. My guess is that in the case of LLM output that is a response to a purely factual question, or a response to a question asking a technological question where I present it with something I know occurs but want to know the means by which it occurs, the amount of hallucination is much less than 10%. And if you have some background in the area you are asking about, you can easily filter out some of what is hallucinated, making the learned material well about 90%. But I’m just guessing based on my experience of asking LLMs a lot of questions about both things I already know quite well and others that I don’t. So, which benchmarks are you talking about?
There is some small losses, it does not run 'forever'.
However the superconducting switch is pretty neat. It's a small section of superconductor between the ends of the coil, but is wrapped in a heating element. When the coils is first powered up the element is heated and the material has a resistance. When the coil is ready the heating element is turned off and the shorted conductor cools down and starts superconducting.
If it's a loop of superconducting material, which seems likely as that's how you prevent losses, then you don't have to supply current so there's no current to stop supplying.
The journalist missed a golden opportunity for education here: 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.
If people don't know about the magnet, or don't know that it can't be turned off (or perhaps assume it's "off" because the scan was over, as I would guess happened here), accidents happen.