# No metal in MRI--why are headphones OK? **URL:** \ **Category:** Factual Questions\ **Created:** [December 6, 2016, 2:23pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018 "2016-12-06T14:23:05Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [December 6, 2016, 2:23pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/1 "2016-12-06T14:23:05Z")
I had an MRI earlier this year and was cautioned about having any metal on me, and they wanted a full inventory of any medical metal I might have in my body (none). But then they put a pair of headphones on me so I can listen to music (every genre except jazz :smack:) during the test. Why are headphones OK in an MRI machine but not any other metal? Headphones even have magnets in them. ---
**Author:** ![Ispolkom](https://avatars.discourse-cdn.com/v4/letter/i/e47774/32.png) [@Ispolkom](https://boards.straightdope.com/u/Ispolkom)\ **Post date:** [December 6, 2016, 2:30pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/2 "2016-12-06T14:30:59Z")
The headphones you use in an MRI are nonmetallic. They are connected to an external speaker by a hollow tube – very low-tech. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 6, 2016, 3:04pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/3 "2016-12-06T15:04:53Z")
> [@Ispolkom](#): > > The headphones you use in an MRI are nonmetallic. They are connected to an external speaker by a hollow tube – very low-tech. [Here’s one,](http://www.mriequip.com/store/pc/viewPrd.asp?idproduct=317) with a fairly complete technical description. The reminds me of the headphones you used to get on international flights back in the 1970s; they were all-plastic construction, just pneumatic tubes that you plugged into the armrest, with the whole system functioning a bit like a [speaking tube.](https://en.wikipedia.org/wiki/Speaking_tube). Always wondered where the driver was that was moving that air. Surely there wasn’t one speaker for every seat? Maybe one for every row? ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [December 6, 2016, 3:20pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/4 "2016-12-06T15:20:08Z")
I always wonder about the gold in my teeth. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [December 6, 2016, 3:38pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/5 "2016-12-06T15:38:28Z")
> [@Ispolkom](#): > > The headphones you use in an MRI are nonmetallic. They are connected to an external speaker by a hollow tube – very low-tech. That explains the shitty sound quality. ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [December 6, 2016, 4:34pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/6 "2016-12-06T16:34:19Z")
> [@Chefguy](#): > > I always wonder about the gold in my teeth. Well, at least it gives you something to think about during the 20 minutes of absolute immobility during the test. THRUM THRUM BANGBANGBANG MRRRRRRRRRR VIPVIP THRUM Gold isn’t magnetiTHRUM BANGBANG … what was I saying again? Oh yea, neither is titanMRRRRRRRR CLICKCLICK MRRRRRRRRRRRRRRRR… titanium. or medical stainlesBRACCCCCKKKK MRRRRR ok that was a loud one. ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [December 6, 2016, 6:09pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/7 "2016-12-06T18:09:16Z")
> [@Just\_Asking\_Questions](#): > > Well, at least it gives you something to think about during the 20 minutes of absolute immobility during the test. Which is much better than have an allergic reaction to the contrast dye. Ask me how I know… ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [December 6, 2016, 6:13pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/8 "2016-12-06T18:13:57Z")
> [@Just\_Asking\_Questions](#): > > Well, at least it gives you something to think about during the 20 minutes of absolute immobility during the test. THRUM THRUM BANGBANGBANG MRRRRRRRRRR VIPVIP THRUM > > Gold isn’t magnetiTHRUM BANGBANG … what was I saying again? Oh yea, neither is titanMRRRRRRRR CLICKCLICK MRRRRRRRRRRRRRRRR… titanium. or medical stainlesBRACCCCCKKKK MRRRRR ok that was a loud one. You might be interested in this article about how MRI design was modified at a children’s hospital [Creative Confidence: A new book from IDEO's Tom and David Kelley](http://www.slate.com/blogs/the_eye/2013/10/18/creative_confidence_a_new_book_from_ideo_s_tom_and_david_kelley.html) ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [December 6, 2016, 6:21pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/9 "2016-12-06T18:21:57Z")
> [@Andy\_L](#): > > You might be interested in this article about how MRI design was modified at a children’s hospital [Creative Confidence: A new book from IDEO's Tom and David Kelley](http://www.slate.com/blogs/the_eye/2013/10/18/creative_confidence_a_new_book_from_ideo_s_tom_and_david_kelley.html) I want the space ship one. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [December 6, 2016, 6:36pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/10 "2016-12-06T18:36:27Z")
> [@Machine\_Elf](#): > > The reminds me of the headphones you used to get on international flights back in the 1970s; they were all-plastic construction, just pneumatic tubes that you plugged into the armrest, with the whole system functioning a bit like a [speaking tube.](https://en.wikipedia.org/wiki/Speaking_tube). Always wondered where the driver was that was moving that air. Surely there wasn’t one speaker for every seat? Maybe one for every row? I’d see those on domestic flights, too, until fairly recently (I think it’s only been the past few years where they finally gave up on that system). I’d always wondered about the tech behind those, too. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 6, 2016, 6:47pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/11 "2016-12-06T18:47:05Z")
> [@kenobi\_65](#): > > I’d see those on domestic flights, too, until fairly recently (I think it’s only been the past few years where they finally gave up on that system). I’d always wondered about the tech behind those, too. According to [Wikipedia,](https://en.wikipedia.org/wiki/In-flight_entertainment#History) Delta was the last airline still using them, and stopped in 2003. Apparently pneumatic headphones used to be dirt-cheap, but over time it became economical to hand out electric ear buds like candy. More info [here,](http://aviation.stackexchange.com/questions/14536/why-were-there-pneumatic-headphones-on-airliners-in-the-70s-and-80s) and here: [Pneumatic Airline Music, Greatly Missed](http://www.brandlandusa.com/2008/06/07/pneumatic-airline-music-greatly-missed/) ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [December 6, 2016, 6:49pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/12 "2016-12-06T18:49:18Z")
You think that’s disconcerting… Try having to answer “Yes” to “Have you ever had metal filings in your eyes?” Then they ask you a couple of questions about it, shrug, and conclude “It should be OK.” ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [December 6, 2016, 7:00pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/13 "2016-12-06T19:00:24Z")
> [@Machine\_Elf](#): > > According to [Wikipedia,](https://en.wikipedia.org/wiki/In-flight_entertainment#History) Delta was the last airline still using them, and stopped in 2003. Apparently pneumatic headphones used to be dirt-cheap, but over time it became economical to hand out electric ear buds like candy. > > More info [here,](http://aviation.stackexchange.com/questions/14536/why-were-there-pneumatic-headphones-on-airliners-in-the-70s-and-80s) and here: > > [Pneumatic Airline Music, Greatly Missed](http://www.brandlandusa.com/2008/06/07/pneumatic-airline-music-greatly-missed/) Hmm, longer ago than I realized. Thanks! ---
**Author:** ![Emergency911](https://avatars.discourse-cdn.com/v4/letter/e/43a26b/32.png) [@Emergency911](https://boards.straightdope.com/u/Emergency911)\ **Post date:** [December 6, 2016, 7:11pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/14 "2016-12-06T19:11:32Z")
> [@Sparky812](#): > > You think that’s disconcerting… > Try having to answer “Yes” to “Have you ever had metal filings in your eyes?” Then they ask you a couple of questions about it, shrug, and conclude “It should be OK.” I feel your pain. I had some bulging disc issues a few years ago and ended up having several MRI’s. They were all at the same place, but I never managed to get the same person, so I had to go through all the questions each time. By the time I finished getting all the MRI’s, I think I knew the questions better than they did. The thing I disliked the most about the MRI questions were how many times I was asked if I was claustrophobic. Them: “Are you claustrophobic?” Me: “no” Them: “Have you ever been claustrophobic?” Me: “no” Them: “Have you ever had problems with tight/enclosed spaces?” Me: (Sigh)…“no” Them: “Are you sure you aren’t claustrophobic?” Me: (Siiiiighhhh)…“I am sure” By the time they are done trying to convince me that I might be claustrophobic, I am beginning to wonder if I could be claustrophobic and just didn’t know it. Then they slide me in the tube and tell me to be as still as possible. Since I have been in so much pain for so long, I wasn’t sleeping well, so any time I sat still, I would fall asleep; then I would move, which would hurt, which would wake me up. Being that there isn’t a lot of room to move and they would strap me in, I was able to lie fairly still and would fall asleep within a few minutes, which would always amaze these folks. They would always say they have never had someone fall asleep in the machine, I would beg them to put something in my chart that would tell the next person that I was truly comfortable with enclosed spaces and there was no need for all the claustrophobic questions, but they never did. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [December 6, 2016, 8:35pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/15 "2016-12-06T20:35:35Z")
> [@Chefguy](#): > > I always wonder about the gold in my teeth. The magnetic fields in MRI machines only affect [ferromagnetic](https://en.wikipedia.org/wiki/Ferromagnetism) materials, the most common of which include iron, nickel, cobalt, and their alloys. [Cite](https://www.biac.duke.edu/research/safety/tutorial.asp). So your gold teeth are fine unless they are alloyed with a ferromagnetic material. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 6, 2016, 9:26pm UTC](https://boards.straightdope.com/t/no-metal-in-mri-why-are-headphones-ok/774018/16 "2016-12-06T21:26:11Z")
> [@robby](#): > > The magnetic fields in MRI machines only affect [ferromagnetic](https://en.wikipedia.org/wiki/Ferromagnetism) materials, the most common of which include iron, nickel, cobalt, and their alloys. [Cite](https://www.biac.duke.edu/research/safety/tutorial.asp). > > So your gold teeth are fine unless they are alloyed with a ferromagnetic material. From your cite, the static magnetic field only affects ferromagnetic materials. But the [time-varying magnetic field can induce electrical currents in other metals:](https://www.biac.duke.edu/research/safety/tutorial.asp#TVM_2) > [@Duke](#): > > As reviewed in the section on RF fields, interference with an implanted medical device may result from both RF fields and by induction of currents within the device by dB/dt. Also, currents may be induced within implanted control wires, even if the device has been removed. > > These examples were reported to the FDA. > •MDR-351516: A patient with an implanted cardiac pacemaker died during an MR exam. (12/2/92) > •MDR-175218: A patient with an implanted cardiac pacemaker died during or shortly after an MR exam. The coroner determined that the death was due to the interruption of the pacemaker by the MR system. (9/18/89) > > The best means to address these risks are the same as for avoiding the risks associated with RF fields, carefully screen subjects and exclude those with implanted medical devices.