I have a pacemaker and was told I cold never have an MRI. Couldn’t they manufacturer the pacemaker out of non-ferrous (or non-ferromagnetic) materials? Why not? I was also told it was perfectly OK to go through an airport metal detector (which doesn’t even always detect it, although some of them do).
It’s not just the metal, it’s the electrical aspects. The MRI could induce a current in the pacemaker wire, and that would be a Very Bad Thing[sup]TM[/sup]. An airport metal detector is using a much, much smaller magnetic field and so it’s not a problem.
Nothing upsetting about it. Besides, as I said, this was a brand-new 300 MHz NMR, not a MRI. But I don’t want to see another NMR quench because of the down time and cost involved. And I wouldn’t want to be inside an MRI when one happened. I’d expect it to be possibly scary (depending on where the gas came out), and a ton of bother. If nothing else, you’d have to make a new appointment for when the instrument was up and running again.
What do you understand is the difference between MRI and NMR? I thought they just changed the name because the “nuclear” in NMR upset some people. In fact, the first time I had it done, they DID call it NMR. They both do imaging with nuclear magnetic resonance, unless you are referring to a device that does NMR of a small sample to produce a single spectrum, at a single point, without imaging. The single-point NMR devices I have seen or used are small, with samples that fit in vials rather than samples that walk in with insurance cards. Even with some huge 30 T field intensity, their dewars wouldn’t hold much, would they?
Thanks for the explanation.
Yeah it was the third MRI I had had with this particular doctor, and so we were quite chatty. We started to go through the metals checklist, and got chatting about my glasses, and their metal content. I guess we skipped a step during the chat!
pdts
Here’s what it takes to remove a chair from an MRI
Loose gurney in room
Small tank vs watermelon
Large oxy tank
I’ve had metal filings in my eyes, haven’t asked a doc yet but was told by other people that once that’s happened they’ll never give you an mri because they’re worried there still might be metal you eye and it’ll spin and make you blind. Any truth to that?
Does it actually hurt if you have a tattoo and get an mri?
I have metal fillings in my teeth and my malar bone has been wired back in place. I’ve had an MRI – no problems.
Usually if someone has a history of metalworking, a plain x-ray of the skull and orbits will be taken to rule out a metallic fragment near the eye, because the magnet could rip the metal piece out.
Tattoos that have enough metal to heat up are not common, but they give the patient a panic button to push if anything starts to go wrong.
.
I have a piece of ferrous metal imbedded in my shin. What it is, exactly, and how I got it are both unknown, but it hasn’t moved through two MRI’s on my knees. It could be very deeply imbedded, or covered by calcium, but I’m not curious enough to let them cut my leg open to find out.
Wasn’t this proved wrong on Mythbusters?
Note that MHz is a measure of frequency, not magnetic field strength.
However, assuming the 500MHz relates to the frequency of proton precession, the field strength can be calculated. For 500MHz, it’s about 12 tesla.
For medical applications, 3T has become pretty standard now, although there are still plenty of 1.5T machines around.
There are a handful of 7T machines around, worldwide, and only one or two of around 11T and the latter are in the testing phase, rather than being used routinely on patients.
It’s much harder to make clinical MRI machines, mainly because of the difficulties of creating a uniform field over the diameter of the patient.
I am well aware of the difference between a clinical MRI and the Bruker NMR I used the other day to analyze a compound I synthesized. All the chemists I know use the language as I have to differentiate between a clinical NMR used in medical imaging and a single-sample NMR to obtain various spectra of chemical compounds.
It doesn’t take much liquid helium to quickly expand to a large amount of gas. I have no idea what the density of liquid helium is, but consider that a mole of helium weighs 4.00 g. After all, one mole of gas is 22.4 L, and a quenched NMR could release up to 100 cubic meters of gas. That’d be more than enough to cause an asphyxiation risk in a small room and I’ve used NMRs kept in some pretty small rooms.
I’m not allowed to get an MRI because of a medical implant. I will definately observe this rule after reading it could rip out of my flesh… :eek: I don’t set of metal detectors though?
So what’s the correct procedure for taking an NMR offline (e.g., to move it)? Power down the magnet while keeping it cold? How do they do that?
The magnet is always on!
This is just about the first thing that will be drilled into your head if you woark anywhere near an MRI room. Other than a quench, there’s really no “off” switch for the magnet.
A paperclip will get up to about 40 MPH with a 1.5T magnet. It may not kill you, but it’s certainly going to sting. A stronger magnet will accelerate things even faster.
It gets really interesting when police officers are involved - there have been a few cases of guns being sucked into the bore. In one documented case, a firearm discharged with the safety on because the massive magnetic field moved the internal firing mechanism.
I don’t think they tested all possible variants of tattoos and inks, but it would in theory require a large tattoo in the proper orientation with a metallic ink. It’s a theoretical risk, but not a daily issue by any means.
The panic button is there for whatever is causing a problem.
In '94 I had to visit the ER because of a steel fleck embedded in my cornea. 12 years later I had to get an MRI, and told them about the fleck. I was pretty sure they had completely removed it in '94, but the MRI folks required an X-ray to verify that there was no ferrous material remaining in my eye. If they’re worried about metal in your eyes, they’ll X-ray you to be sure.
My fear is that I will get in an accident and they will throw me in the MRI machine. If I am unconsious I can’t tell them. Hopefull they will see the scar on my back. I should get a medical ID tag.