Many people just learning about MRI safety and hazards ask very similar questions. One of most frequent is, “why do I have to remove all metal before an MRI,” or it’s corollary, “can I get an MRI with some metal on (or in) me?” To answer these questions, let’s start at the very beginning…
As far as the MRI machine is concerned, there are two different types of metal, ferromagnetic and non-ferromagnetic. You may remember back to high school chemistry and the periodic table of elements where many of us learned (and then promptly forgot) that Fe is the symbol for iron.
Fe - Iron from the Periodic Table
“Fe”, the symbol, is derived from ferrum, the Latin word for iron. Ferromagnetic does not mean that a metal contains iron, but rather that the material has magnetic properties as iron can.
Ferromagnetic metals are iron, cobalt and nickel. These raw ingredients are common in many, many things made from metal, including (likely) the steel grommets in your shoes, to the zipper in your pants, to components in your wristwatch. Another common area to find these metals is in batteries, such as those found in your hearing aid, cell phone and iPod. There are a few non-metal ferromagnetic materials, but these are not very common.
Alright, alright, already… enough chemistry. What does this mean?
When exposed to magnetic fields, ferromagnetic materials become magnets themselves. You can prove this yourself with a fridge-door magnet and a few paper clips. You’ll probably find that paper clips right out of the box aren’t capable of magnetically ‘sticking’ to one another. If you stick one to a chunky fridge-door magnet, however, that paper clip is now magnetized and will likely be able to magnetically ‘stick’ to another paper clip. The length of the magnetic chain of paper clips you can create is a function of how strong the fridge-door magnet is and the magnetic properties of the paper clip steel.
Now, the exact same thing happens with ferromagnetic metals approaching the MRI, but a crucial difference is the distance at which the materials get attracted. With your fridge-door magnet test, the paper clip needs to be touching (or very nearly so) the magnet before the attractive effects are felt. MRI’s, by virtue of the fact that they’re both 1,000′s of time stronger and larger than your fridge-door magnet, can exert profound attractive force at a good distance away from the magnet.
The size and strength of MRI magnets is so great that people have been trapped, injured, and even killed by the force of ferromagnetic objects attracted to the MRI. From concealed roller-skate tennis shoes, to steel-reinforced furniture, to conventional hospital wheelchairs and gurneys, to steel oxygen cylinders, all of these normally harmless (outside the MRI suite) items become life-threatening when subjected to the enormous pull of the MRI’s magnet.
Not all metals are ferromagnetic. In fact, in an MRI suite a concerted effort is usually made to rid the area of ferromagnetic materials and use non-ferromagnetic replacements whenever possible. Non-ferromagnetic metals include aluminum, titanium, brass, copper, and many others. These (and other) non-ferromagnetic metals can present other problems and hazards during MRI imaging, but that’s a topic for another day.
It is almost impossible to determine whether a material is ferromagnetic just by looking at it. In fact, even sometimes when you know what an object is made of, it still isn’t enough to know whether it’s ferromagnetic or not. Stainless steel, is one of these examples.
Stainless steel is not a metal, but rather a family of recipes for metal. Some stainless steel ‘recipes’ (alloys) call for ingredients with ferromagnetic properties. Others which include ferromagnetic ingredients are specially formulated to change the structure of magnetic materials into non-magnetic versions of the material. These special ‘de-magnetized’ stainless steels can become ferromagnetic if the steel is manipulated (shaped, bent, heated, or stressed), so even magnetically ‘safe’ stainless steels can become ‘unsafe’ under certain circumstances (a change that isn’t observable to the eye).
It is remarkably difficult to distinguish magnetically ‘safe’ metals from magnetically ‘unsafe’ metals, either by simply looking at them or, sometimes, even if you know what the metal is. As a result, MRI facilities must assume all metals to be magnetically unsafe unless and until they’ve been verified to be non-magnetic.
So, how do MRI facilities distinguish magnet-unsafe metals? They can use magnets, which shouldn’t be used on patients or sensitive equipment, limiting their applicability. The safer option (and arguably more effective, to boot) is to use a ferromagnetic detector, at least on patients and sensitive equipment.
Ferromagnetic detection instruments, such as the Mednovus products, should be used to help identify magnetically-unsafe materials. This is the standard established by the American College of Radiology, the VA’s MRI Design Guide, and even recommended by the Joint Commission in Sentinel Event Alert #38.
As a patient, it is vital to take seriously the admonitions against wearing or carrying metal into the MRI suite. If you have shrapnel, penetrating metal injuries (particularly in the eye), or any surgeries, implants or prosthetics, it’s critical to have the full information on each to share with your MRI provider. Metal inside the body may not fly across the MRI room like a loose oxygen cylinder (don’t believe what you see on House), but the twisting an pulling that the magnet will exert on an internal ferromagnetic object can be just as dangerous. Active implanted devices, such as pacemakers or nerve stimulators, present particular problems because of both the magnetic attraction and potential interference with the normal function of the device.
Patients should also actively seek out MRI providers that conform with the contemporary safety recommendations, including the use of ferromagnetic detection. You can even contact Mednovus when you want to find providers near you who have this technology available.
Providers of MRI services should make sure that the pre-screening and safety services they provide are in accord with the contemporary best practices, including the use of ferromagnetic detection. With available ferromagnetic detection products equal in cost to only a few hours worth of technical revenue, there’s no financial rationale for not providing this valuable safety benefit to patients and staff. Plus, when weighed against the costs of ferromagnetic object accidents, these instruments of safety are clearly effective risk-management investments.
In all cases, metal brought to the MRI suite (either inside or outside the body of the visitor) should be scrutinized by a trained MRI staff person. This investigation should be aided through the use of ferromagnetic detectors, both to help characterize the hazards of any particular object and to help find ferromagnetic materials that weren’t caught in the prior screening process.
Tobias Gilk, President & MRI Safety Director Mednovus, Inc. Tobias.Gilk@Mednovus.com www.MEDNOVUS.com
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I was browsing for related blog posts for my project research and I happened to stumble upon this. Thanks for the great info.
I have been an MRI Assistant for 7 years, and I am often confronted by patients that don’t understand the potential for harm from implants, metal on clothing/metallic accessories, shrapnel-related injuries, etc. I really appreciate that this information is available for those who are interested.
I have weave extensions that are sowed in a black plastic sreen in my hair… would that effect my MRI?
Yvette,
Sometimes weaves / extensions are attached to existing hair with wires which could be plastic coated. Any metal (whether it’s a magnetic metal or not) can affect the outcome of an MRI scan if it’s near enough to the area being scanned. Yes, it is possible that this could affect your scan.
Tobias Gilk
I am about to be scheduled for a MRI on my shoulder. About 2 years ago a stent was placed in my galbladder duct. As recent as 9 months ago an X-ray was made which showed the stent is still in place. Question: Can the Doctor who placed the stent tell me if it is safe for me to have the MRI? I of course, will advise the MRI folks of this problem.
Any suggestions?
Thank you, Joe Davis
Joe,
The conditions in which a particular device (or stent) are safe or dangerous often depend on a number of factors (magnet strength, orientation relative to the magnetic field, anatomy being imaged, the types of MRI coils – like antennae – being used, etc…). The doctor who put the stent in probably doesn’t have the first clue about how the radiologist will want the MRI study done, so I would be dubious of any blanket statement from the referring physician about the safety of the stent.
What I would expect the referring physician to provide is complete information on exactly what that stent is (manufacturer, model, serial number, length, position, etc…). With this information, the radiologist can determine what would be the best way to get you your MRI, or whether it’s an unnecessary risk because of the stent.
I hope this helps.
What about patients who used to have Cobalt/Chromium implants and now have metallosis?
Could an MRI potentially pose a risk from the metal levels in their blood stream?
I think that the only way that small magnetic particulate could be of potential risk would be if there was enough aggregate material which, if it collected in a single artery or vein, held in place by the magnet’s magnetic field, and caused a blockage. I don’t know that there would be any other unique potentially harmful interactions between an MRI and free-flowing metal particulate.
Tobias Gilk
I am a General Contractor working on a new MRI suite at a Joint Commission Hospital in Northern Virginia and I have run into a problem. The stainless steel parts for the cabinet drawers (the drawer slides) are not compatible with the MRI’s magnetic field, and I am having trouble finding a suitable replacement part. Could you direct me to any companies that provide MRI safe hardware or materials? Your article on the ferromagnetic metals was very informative as well.
Thank you,
Patrick Bolton
ADI Construction
Patrick,
Generally stainless steel is only very weakly ferromagnetic and should not be a threat if (a) it is firmly secured and, (b) not very near the magnet. I would recommend using non-ferromagnetic screws (because even if the glides are largely non-ferromagnetic, it doesn’t mean that the fasteners are). If you remain concerned, you can use a continuous rail guide of whatever material the casework is made from. Often melamine on melamine (with a touch of talcum powder, if it needs a little lubricant) creates a fine glide for drawers. If you’ve got a particularly heavy load in a drawer or on the glides, then finding the least magnetic ball-bearing glide is your best bet.
Even better than built-ins are rolling casework for the magnet room. If this is an option for you, I know that Mass Medical (Mass Cabinets) makes MR-friendly rolling casegoods.
Tobias Gilk
I plan MRI of thyroid gland and have two problems:
1. my dental prostheses ( so called bridge made of stainless steel)
2. uterine spiral implant Copper T (model T Cu 380A)
Most dental implants are not, by themselves, contraindications for MRI exams. Typically these are made of low-magnetic materials and are not dangerous. Regardless of this generalization, it is essential that you share as much information about these implants with the technologist / radiographer who will be administering your MRI exam.
Depending on the coils that they use for your exam (these are essentially focusing tools to take ‘pictures’ of particular parts of the body), the uterine implant may (or may not) be subject to the heating risks. Again, it’s critical to discuss this with the tech / radiographer prior to your exam to make sure that the safest and most effective means of getting the clinical image are planned out.
I hope this helps.
I’ve just returned from an MRI, which I had to abandon, due to a panic attack. I panicked because I thought I felt something moving in one eye during the process (only way I can describe it is as if someone was drawing a pen line on my eyelid, but inside my eyeball – every half minute / minute or so? I had to get out of there after the 3rd time this happened).
Since childhood, I’ve often got things in my eyes (including bits of metal), but always thought this had been removed (I never went to hospital for this, which is one reason I didn’t mention it on the hospital form – the question was have you ever had metal in your eye that a hospital was unable to remove). So when asked by the tech. as to whether I had any metal in my eye, I said not to my knowledge. I couldn’t remember where/when I had incidents, so had no definite info. to give the hospital, also
Of my experiences with metal in the eye, this was mostly copper or aluminium, but I had a vague recollection of getting ferrous metal in my eye. When I got home, in talking to my husband, I remembered this was when I used a wire brush to remove rust from a radiator a few years ago
So I’m now a bit concerned that I still have something in my eye, and that having an MRI has done some damage. However, if I do, wouldn’t such ‘movement’ have hurt? (I still have full sight, and there is no pain) Should I mention it to the Dr when I next see him?
OK, so you knew that there was a concern about metal objects in your eye, and you knew that you’d had metal objects in your eye, but you parsed the intended meaning of the question to exclude the answer that you think that the radiographer was looking for???
I think that the fact that you don’t appear to have damage to your eyesight, and your eye didn’t inflame, is a product of pure luck. Don’t push that luck any further than you already have.
Our eyes don’t have pain receptors like those elsewhere in the body, so yes, it is entirely possible to have something in there that you didn’t feel before the exam, and that the ‘movement’ that you did feel during the MRI didn’t have pain associated with it.
I would unequivocally recommend that you discuss this with your doctor. If your doctor wanted you to get an MRI exam, you should still work towards that objective (he or she proscribed for a reason, after all). But you should be thoroughly screened for a metallic foreign body in your eyes (even the one in which you didn’t feel the movement) before you re-attempt the MRI.
Small metal fragments can be difficult to see on a conventional X-ray, so your doctor may want to proscribe a set of thin-slice CT images through your eyes to see if they can better find this culprit.
Please do return after you’ve had this talk with your doctor and let us know how that turned out.
Tobias
Thanks for the information, Tobias.
I should have mentioned that I have learning difficulties, and have problems with understanding and answering questions – I tend to take things very literally, and I also have very poor memory. Though I’m ususally not aware of how I am. Sadly due to cut-backs, I am no longer entitled to welfare support to help me out with such situations (my disabilities prevent me working). As far as I was aware, I did as I supposed to, answering the questions on the form, and by the staff, properly (but I realise I didn’t do good).
When I tell people I don’t understand forms and need help filling them in (due to learning difficulties), they firstly laugh; then they just slowly shout the questions at me, exactly as printed on the forms. I hasten to add that I had to do this before I reached the MRI dept. – the MRI staff were lovely
And I was so pleased to have (in my mind!) done what exactly they asked of me – finding clothes containing no metal: not that easy! So I’m disappointed I messed up with communications : (
Thanks for the info. on the CT vs. x-ray. I was having the MRI to double check that I don’t have MS, but as this was seen as being unlikely by the Neurologist, I’m electing not to go back for an MRI. It was all too frightening for me.
Thanks for the info. regarding eyes & pain – I shall speak to my GP
And Tobias, as someone who has problems in understanding, I congratulate you on your clear presentation and explanation of facts, which are very interesting 8 )
Polly,
I’m sorry to not have known about your challenges with regard to forms and I hope I didn’t come across as sanctimonious.
If your GP thinks that the MRI exam will be helpful, I would encourage you to get it (with the eye screening first, of course). If, together, you elect not to go forward with the MRI, I would still strongly recommend that you get the eye screening.
Tobias
Thank you Tobias,
No, you didn’t come across as sanctimonious – I understand that it must be frustrating when anyone doesn’t abide by the safety rules, for whatever reason – especially when it’s for their own good!
As my eye did feel uncomfortable on the night of the MRI, and it now actually feels as if there’s something there (hasn’t stopped itching since – just in the place where a tiny grey speck has appeared), I’m going to have my eye screened as soon as I can.
But maybe my story will encourage other readers to think about their own history of eye injuries, before they have an MRI, and if there’s any chance they’ve EVER had metal in their eye, to tell the MRI dept. about it, in advance, so they can have it checked out first!! This was a frightening experience that I wouldn’t want others to go through, and I realise I’m lucky
Thanks again for the advice
i had a mri today and forgot to take off my watch.. no burn but itchy wrist. is there a long term concern? thanks
It’s always best to remove everything metallic before an MRI scan (actually, before you even enter the room). Your watch band may have vibrated during the scan, which could have triggered the itching sensation. I wouldn’t be worried about any lasting effects. While MRI-related burns can take upwards of an hour to materialize, any mild irritation is likely not very serious.
If it persists, or gets worse, you should see your doctor… In no small part because whatever you’re experiencing may be serious, though completely unrelated to your MRI scan.
I went for a brain MRI yesterday and completely forgot to take off my cartliage earing.Ive had it in since i was a kid and never take it off. I actually forgot i even had one. Is that going to effect the results of the test?
Kait,
You’re probably ok. Yes, metal near the anatomy being imaged can interfere with the scan. How much depends on quite a number of factors, including the size, shape, and metallurgical makeup of the earring, as well as the strength of the magnetic field of the MRI and the specific image parameters they were using.
Hopefully, the tech would have noticed the problem, had there been one. If you are concerned, ask your physician when he or she reviews the scan with you.
Next time, however, make sure to remember to remove *all* metal. Not only is it much safer, it can also help to protect the quality of your MRI scan image.
I would like a response please. Today I had an MRI of my spine and the tech ask what kinds of surgery had I had and I told them they explained that I had a lot of metal fragments left behind from surgery’s no one has ever told me this before I am having lots of pain in the right side of my stomach and back I thought maybe it could be from old adhesions causing the continual pain in my stomach and into my back but could these metal fragments be causing problems and needs to be removed? You can’t get a doctor to talk to you about removing old adhesions I had a complete hystorectomy at the age of 20 and was told I had endometrosis so bad every thing had to be scraped moved and placed back in and that I would have problems later now no one will listen I need some relief do you have any ideas who I should see?
Please answer if you can.
Thank you, Bonnie
Bonnie,
I’m sorry to hear about your difficulty. Metal, particularly magnetic metals, have a substantial affect on MRI images, which is likely what lead them to say what they did.
I’m not a doctor, so I can’t suggest a diagnosis or treatment to help you. I do hope that you find a physician who can help you, and I wish you the best. I’m sorry I can’t be more direct help to you.
Hi, i googled MRI and found here.
I have leg pain and MRI on my back is scheduled. But i had gold needle insertion in my back 10 years ago. I forgot to mention to my doctor. Mri center said gold is ok. But my concern is the gold needle may not be pure gold. It could have been 24k or some mixed gold. The needles were 1-2mm long, 10-20 were inserted, and the acupuncurist said it will melt. But i don’t think that’s the case. I never took X-ray since then, so I don’t they are still in my back. Would the acupuncture needle be affected by mri machine? (are they going to move inside my spines?) If so, should I take CT instead?
If you are concerned, you could ask the MRI center about getting an X-ray of your back… that could show whether those needles are there. I don’t know how a metal needle would ‘melt’ in your back.
If the needles are only 1 to 2 mm long, that’s pretty tiny. Even if they were raw iron, the most magnetic metal, at such a small size I don’t think that they would experience much attractive force. They might vibrate during an MRI exam, and feel odd (even uncomfortable), but I think that it’s definitely within the realm that a radiologist with the MRI center should (perhaps with the benefit of an X-ray) work with you to make an informed decision about whether or not to proceed with the MRI scan.
I hope this helps.