What do movies always get wrong about your job/hobby?
What do movies always get wrong about your job/hobby?
185 comments
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MRIs
Far too many movies and TV shows use the magnet to cover for their lazy writing by treating it like something that can be turned on and off like a light.
The magnet in an MRI is one of the coolest things in medicine, and writers get it wrong all the time. In the vast majority of cases, it's always on.
In simple terms, an electromagnet works by running a current in a circle and creating a magnetic field. In an MRI, the current is flowing in what is essentially a closed loop of wire. However, in this case the wire is cooled with liquid helium so it becomes a superconductor.
They induce a current in the wire which creates the magnetic field ("ramp up" the magnet). Because it is superconducting, the current doesn't stop. Once it's ramped up, it no longer requires any external power. As long as the current is flowing the magnetic field remains.
There are only two ways to "turn off" the magnet.
One way is to "ramp down". Essentially the opposite process that is used to get it running in the first place. That's what they do if they need to stop it for service.
The other way is to quench the magnet. You hit the emergency stop and vent off the liquid helium. Without the helium, the wire warms and resists the current and the flow stops.
Quenching a magnet is a magnificently dramatic process. Someone hits the panic button, and there is a loud roar as the helium escapes. Clouds of condensation form around the exterior of the building as the cold gas escapes. In the event some construction crew screwed up and accidentally sealed the vents, there could be an explosion from the rapidly expanding gas.
If writers want to use an MRI as a plot device, have an accident and require someone to quench the magnet to save a life. You'd have the immediate drama from the accident and the quench, and then you'd have the long term drama of the hospital trying to figure out where the money to fix the MRI would come from.
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I remember reading an article from a few years ago a cop brought a handgun into the room after ignoring staff warnings... Then, hit the quench button.
EDIT: it was last year. https://ktla.com/news/local-news/lapd-officer-lost-gun-in-mri-machine-during-mistargeted-raid-report-says/
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that is SO cool, can you write dick wolf
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Dick won't accept my correspondence!
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The magnet in an MRI is one of the coolest things in medicine
Literally and figuratively!
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I used to install and maintain MRIs (as well as some other medical imaging modalities) and this seems to be wrong any time I've ever seen it in media.
- people will be shown in the magnet room with steel wheelchairs/patient tables/chairs/etc. or even their phones. None of that should be entering the room at all.
- the images shown on the diagnostics will be like a radiogram or PET or something that would not show from an MRI.
- the scan only takes a minute for a "picture", when in reality having an MRI scan can easily take an hour. You may have some people taking only 15 minutes or so, but those are the quick ones. Clinicians will order a whole list of scans and each one takes several minutes.
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Years ago where I work a resident decided to be helpful and move a patient into the room with the MRI.
Of course, the patient was supposed to be transferred off the ferrous metal gurney before coming into the room. The resident didn't know that.
The MRI pulled the gurney into the room and it slammed into the scanner. Luckily it didn't actually flip up and crush the patient.
They told the patient to stay where he was and they loaded the gurney down with a bunch of full five gallon water bottles. Once they had enough weight on it, they transferred the patient off the gurney. A bunch of guys pulled the gurney out of the room, amazingly without any damage to the scanner.
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Yes I had two separate occasions of having to remove a ferrous table from a magnet. One was able to be removed with 5 of us pulling (using a tie strap for safety to make sure it didn't fling when we repositioned it), but the other we had to ramp down the magnet to remove from the room.
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How about small things like paperclips and staples? My guess is that it won't be too hard to pull but not so easy to get a good hold.
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Unfortunately they did get in the room sometimes. For the most part, techs are really good about keeping the magnet room clear and not bringing ferrous items inside. However, even when things like that did get inside they really aren't a problem to just pick up with your hands (or sometimes our titanium tools like pliers or a screwdriver to get a better grip on them). The pull is strong, but based off the amount of ferrous material so those things that are just a few grams are not really notable.
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I had no idea that once the current was in the magnet, no more power was required to keep it going.
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Superconducting magnets... superconductors are one of those areas where science gets weird.
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That is insanely interesting never knew that
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It wouldn't be nearly as fast, but why would you not just stop the condenser pump so the helium stops cycling through, causing the freezing, instead of venting it off? Sure, venting it off would be faster, but in the lack of an actual emergency, you'd think you could wait like 5 minutes.
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If it's not an emergency, then you let the vendor follow the procedure they have in place for shutting down the magnet.
Edit:
For example: We had a flood in an MRI room. The vendor was called out to ramp the magnet down so that they could deal with the flood.
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185 comments