Just had an MRI, and during the 90 minute torture session, I had much time to think… and try as I might, I couldn’t come up with a valid reason for the machine to be so loud as to require earplugs and still give you a ringing headache.
It seems that each test or picture has its own little pattern of beeps, grinds, whistles, and clatter. Can’t they just turn the damn sound off and let the technician run the show from the room?
Oh, and I love the “Don’t move, or we start over” bullshit. I have an itch! I have to go to the bathroom!
Wikipedia has this, although it’s not exactly clear.
“Switching of field gradients causes a change in the Lorentz force experienced by the gradient coils, producing minute expansions and contractions of the coil itself”
There are alternative technologies for looking at what is inside your brain. And cheaper ones, morevover !
One consists in introducing electrodes through a little hole in the skull. One can do it through a big hole, too. Another one involves lots of formaldehyde, a drill, some scalpels and a slicer. Tell me which one you prefer ! I’d be glad to help.
Because the procedure isn’t exactly uniform. Different things are happening throughout the procedure. And, more often than not, you are having more than one type of scan. There are T1 and T2 scans. And within those scans, there are many sequences you can do as well.
I have had various MRIs over the years. Most of them have involved the dreaded tunnel. It has never really bothered me until today. Maybe it was the one and one-half hour wait before the MRI. Guess that’s why they call it a waiting room. Anyway, the sound today was absolutely deafening. Are you telling me that they can build a Magnetic Resonance Imaging System and they can’t build a muting system? B.S. I think it’s a conspiracy. The truth is, they make it ridiculously loud so you can’t possibly fall asleep. Fall asleep and you may move. Move, and it’s time to start over. See? That was easy…and believable. Magnets, my ass. Oh, by the way, I still don’t believe Oswald acted alone.
The press release doesn’t say much, but it does say noise is “virtually eliminated at the source”. I’m familiar with noise produced by inductors, which I’d suppose is similar in that the magnetic field physically squeezes the coils and causes them to vibrate. One solution is to reduce the peak frequencies so that the inductors are squeezed more gently. Probably GE is doing something along the same lines.
A question to MRI experts. I can’t have an MRI scan because I had open heart bypass surgery, and apparently have a metal ring on my new Aorta. I never got around to asking what would happen if I was given a MRI. Does anyone know?
I don’t know, but I do know it will demagnetize a brand new MetroCard you may have bought that morning for $20 and absentmindedly stuck in your shirt pocket and forgot about. So, there’s that.
I might be able to dig up a cite for this if necessary, but I know a bit about MRIs because my ex worked on them. Basically, an MRI is a massive magnet, strong enough to effect even non-ferrous metals. Depending on what metal it is, the effect could vary from getting extremely hot - not something you want internally - to being moved around, which could be very quickly lethal.
I’ve heard anecdotes about people with, er, “intimate” piercings that they didn’t mention because they were there with their parents who didn’t know about them, and major problems coming from that. Don’t know if it’s actually true though, but I can’t imagine it would be comfortable.
Stink Fish Pot, sorry about your experience. Hopefully you won’t have to have another anytime soon.
I’ve had a handful of MRIs, though, and I find them rather soothing and usually doze off/zone out a bit. Never found them to be that loud (even when I had a head scan) and there were no earplugs, just regular headphones through which the tech tells you when to breathe. Maybe you had older equipment?
Duke of York, chances are you would get rather torn up internally. :eek: My mom, who is a nurse, told me a story about her hospital where another patient’s O2 tank, in the next room, hit the wall nearest the MRI room due to the magnetic flux. I’ve no doubt the story was exaggerated (aren’t those machines/rooms shielded? what about pens/clipboards/electrical plugs/gurneys in the radiology room itself?) but you definitely do not want to get an MRI with your hardware. My husband forgot his wedding ring for his, and even though it’s mostly gold, had to stop the procedure so he could remove it due to his hand vibrating.
Former MRI tech here - and the simple answer is that the metal ring in/on aorta or wherever would likely experience a torque/twisting-effect when the person is placed within the field (which is always ‘on’). When the various imaging sequences are begun, the changing forces of torque upon the metal can easily cause the ring to bend/move as a whole and possibly tear it out of its normal place. It is also possible to have an induced current produced in circular objects (like rings on hands or things within body like pacemaker leads that happen to have looped during placement, etc). I’ve had plenty of patients tell me their finger’s rings (platinum, gold, titanium,whatever) got warm during scan sequences along with them feeling it trying to turn in various directions/alignments upon their finger while the field was being changed rapidly by scan parameters.
Even non-ferrous items can experience the torque of attempting to line up with the magnetic poles; an aluminum ladder I used to access top of the gantry would try to rotate in my hands as I moved it from one side of gantry to other. Rather odd feeling as one end of 10’ tall ladder would be pulled more than other, but not towards magnet - just a rotation-type movement. There was one nurse who had a necklace with lots of plastic ‘charms’ that had some type of shiny metal ‘paint’ upon them, and whenever she would come to start a difficult IV in scan room, all the charms on her necklace/bracelets would turn and align in same direction but not noticeably being pulled toward gantry at all.
It is usually the torque effect that affects things first (noticeably anyways), and of course there are instances of getting ferrous stuff too close and then becoming missiles flying to the magnet. Surgical implants are always a big worry mostly due to the torque of objects trying to align with field, and if they are shaped in a loop or such then ‘electrical effects’ like heating of the metal from induced current are worrisome.
My father-in-law is one of the directors of a company which makes sophisticated / sensitive metal detectors, specifically for MRI suites. MRI suites are, in theory, shielded to prevent issues with metal items outside of the suite, but some may be better than others. Within the suite, you don’t want any ferrous metal, and other sorts of metal can be problems, as well. Even small items can become projectiles, or become heated by the magnetic field.