47

Can MRIs have any deleterious effect on one's health? Or would it be safe to have say 5 MRIs per year?

Rodrigo de Azevedo
  • 1
  • 3
  • 10
Franck Dernoncourt
  • 10,309
  • 7
  • 40
  • 78

2 Answers2

46

One of the greatest benefits of MRI scans is their safety. Unlike PET, X-ray, CT and most other scans, MRIs use the properties of body tissues in magnetic fields to produce an image. The MRI machine produces a powerful magnetic field which interacts with body tissues to produce radio waves, which are in turn interpreted by a computer to determine the location of the tissues.1

This does not, however, mean MRIs are completely without risk. First and foremost, an MRI machine is basically a giant magnet. If one has metal in his or her body, from a medical implant, car accident, or even an improperly done tattoo, the MRI machine can move it, potentially violently. In the case of medical implants, an MRI machine can easily destroy any electrical components.2 There are a number of different reasons metal might be present in the body.3 This is why MRI technologists are trained to ask, repeatedly, about any metal that may be present.

In addition to metal, some MRIs involve contrast media, chemicals injected or consumed that increase visibility of certain tissues in MRI scans. These chemicals are normally removed by the body rather quickly, and except in individuals with reduced kidney function, are for the most part safe. However, there have been cases of allergic reactions and side effects.4 Also, recently, questionable studies have presented possible links between gadolinium-based contrast agents and nephrogenic systemic fibrosis, though the American FDA has stated that this link is only significant in patients with kidney disease, as "NSF has not been reported in patients with normal kidney function".5

In Short

In healthy individuals, with properly-functioning kidneys, no medical implants, no improperly-done tattoos, and no metal embedded in the body, MRIs are completely safe, once or even quite often.

Community
  • 1
TheEnvironmentalist
  • 3,366
  • 15
  • 31
  • 2
    Good answer, thanks. Explicitly annotated links would be helpful, so people can see what they are about to click. – Faheem Mitha Mar 31 '15 at 21:56
  • @FaheemMitha Bottom left corner of the screen in most browsers, and I'm working on Meta now to implement a better reference system – TheEnvironmentalist Mar 31 '15 at 22:07
  • 1
    Yes, I know I can see the link. :-) I meant, it is helpful if the link is annotated in the question itself, with a title or other suitable material. If you don't want to interrupt the flow of text in the answer, perhaps you could put it at the bottom, like a footnote? – Faheem Mitha Mar 31 '15 at 22:10
  • @FaheemMitha I'd like the references to appear at the bottom of each question, or even (though I'm not sure it's implementable by moderators) upon hovering over the link. The idea is to have references which are available if necessary but do not interrupt the flow of the text. The method I use is the standard in a number of scientific journals. It's even been implemented by Wikipedia, which points to its merit in use by typical internet users. Unfortunately, the best method (visible when hovering) might not be possible here. – TheEnvironmentalist Mar 31 '15 at 22:15
  • I think it is possible to add the links at the bottom and link to them from the main text. But I don't think I've actually done it myself, so I can't tell you how to do it. – Faheem Mitha Mar 31 '15 at 22:23
  • @FaheemMitha that's what I've done here, but while the links appear at the bottom on the question edit page, they don't actually appear in the public question. I would like to move this conversation however to the meta question – TheEnvironmentalist Mar 31 '15 at 22:24
  • Oh, I see. That's unfortunate. – Faheem Mitha Mar 31 '15 at 22:27
  • @TheEnvironmentalist I've edited your question to change around the way the references are presented. It is up to you, but I prefer the way it looks over the previous one, and I think that it flows fairly well. – Tim Apr 09 '15 at 13:09
  • @Tim this question is the basis of a reference debate, so while I certainly acknowledge the usefulness of this method, changing it affects more than just the question. Sorry about that, and thanks a bunch for the input. – TheEnvironmentalist Apr 09 '15 at 15:22
  • @TheEnvironmentalist do feel free to roll back. What do you think of this as an alternative method? – Tim Apr 09 '15 at 15:53
  • I have edited the meta post to have a screenshot of the original, which solve the problem (indirectly). However, it is still 100% your choice of course! – Tim Apr 09 '15 at 16:00
  • 1
    @Tim While I certainly appreciate the effort, it's been nagging me that the meta post now seems like self-promotion. My intent was to present an improvement for the community, not to brag about my answers. My position remains the same. For that reason, as well as improvements in flow and consistency with the medical standard, I have rolled back both. I felt you had every right to know, given the time you put into both. – TheEnvironmentalist Apr 16 '15 at 04:05
  • I think it's useful to add to this answer that noise during MRI scan is very high, making use of earbuds a standard procedure. If earbuds drop during exam, that can lead to damage to sensible or already injured eardrums, though not enough to be permanent.

    Also it's interesting to note that some people with panic syndrome or claustrophobia may need some sedation before the exams.

     – fernacolo Jul 04 '16 at 22:31
  • @TheEnvironmentalist reference [5] link document is removed and no longer available (even on Web Archive). – dev101 Jan 07 '19 at 23:22
  • 1
    @dev101 Noted, and source replaced. I also added some details from the alternative source (FDA) for additional information. – TheEnvironmentalist Jan 08 '19 at 20:52
29

While they're sometimes confused by the public, X-Ray CT (computed tomography) and MRI (magnetic resonance imaging) work by entirely different priniciples. X-Ray radiation is harmful, and any unnecessary exposure should be limited. MRI works by putting the subject into a very strong magnetic field and using radiowaves to excite specific nuclei.

The potential dangers of MRI are equivalent to the dangers of strong magnetic fields and radiowaves (and potentially any contrast medium that is used, which can cause allergic reactions).

According to the FDA:

There are no known harmful side-effects associated with temporary exposure to the strong magnetic field used by MRI scanners.

Due to the strong magnetic field you need to avoid bringing any metal objects near the MRI, they will be attracted by the magnet and become dangerous projectiles.