5 ms·

I wonder if there are any risks to spending a cumulative 20 hours in a MRI machine other than the loud noise he mentioned?

ska 11y ago
None that are known or expected, although I don't believe effect of high field and high field gradients are really well understood. For what its worth there are people who have been in for far more than 20 hours (e.g. hundreds of cumulative hours).
- kaybe 11y ago
  The only biological effect that I know of that uses spin is the detection of the vertical component of Earth's magnetic field in bird eyes. [1] I don't think the effect has been reseached further (such as exposing birds to a very strong magnetic field and see if their perception is altered afterwards, not sure whether that would pass an ethics commitee..) The floating frogs were supposedly fine afterwards. [2] Supposedly, if any long term effects occur, they are subtle. There is a lot we do not know yet - for example, cells seem to be able to communicate through glass. (How? no clue. Photons have been proposed.) [1] eg http://www.physicscentral.com/explore/action/pia-entanglement.cfm http://www.physicscentral.com/explore/action/pia-entanglemen... [2] http://www.ru.nl/hfml/research/levitation/diamagnetic/#Whyfrogs http://www.ru.nl/hfml/research/levitation/diamagnetic/#Whyfr... </rant>
  - Practicality 11y ago
    While I applaud your use of citations, do you have another one for cells being able to communicate through glass? That one seems very interesting.
    - kaybe 11y ago
      Sure, lmgtfy: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660427/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660427/ which is a study from 2009 on the phenomenon.
- brechmos 11y ago
  Agreed. I have been scanned around 1,500 hours over the years and I have not had any ill effects (at this point). And that is 1.5T, 3T and 7T MRI scanners
  - relkor 11y ago
    I am curious as to why you have been scanned so many hours over (?) years. How was that funded? Did you learn anything especially interesting other than no ill effects?
- ihnorton 11y ago
  There can be one effect during diffusion-weighted scanning, which is muscle twitching due to induced depolarization when the gradients are ramped hard. I've had that happen a few times and it was a fairly weird sensation, but not discomforting enough for me to stop the scan. No long-term issues that I'm aware of though.
  - ska 11y ago
    This is called peripheral nerve stimulation (PNS), and isn't specific to EPI (e.g diffusion scans). This That's fair though, I really should have been more specific: You can certainly harm a human being with the piece of machinery known as an MR scanner. Much more so than just PNS, you are dumping energy into the body via RF, so there is a specific absorption rate (SAR) limit applied to avoid going into ranges that will damage tissue. What I was refering to was limited only to the effect of exposure to fixed magnetic fields in an MR, and gradients and RF coils as they are constrained for clinical use.
  - russpoldrack 11y ago
    I had peripheral nerve stimulation nearly every time I did the diffusion weighted scans, but for me too it wasn't bad enough to stop the scan
tormeh 11y ago
Almost all people curious about the brain, especially neuroscientists, experiment (ha!) with drugs. I won't assume MRI is safe, but cocaine isn't safe either. That's just my anecdotally supported prejudice.

ska 11y ago

None that are known or expected, although I don't believe effect of high field and high field gradients are really well understood. For what its worth there are people who have been in for far more than 20 hours (e.g. hundreds of cumulative hours).

kaybe 11y ago
The only biological effect that I know of that uses spin is the detection of the vertical component of Earth's magnetic field in bird eyes. [1] I don't think the effect has been reseached further (such as exposing birds to a very strong magnetic field and see if their perception is altered afterwards, not sure whether that would pass an ethics commitee..) The floating frogs were supposedly fine afterwards. [2] Supposedly, if any long term effects occur, they are subtle. There is a lot we do not know yet - for example, cells seem to be able to communicate through glass. (How? no clue. Photons have been proposed.) [1] eg http://www.physicscentral.com/explore/action/pia-entanglement.cfm http://www.physicscentral.com/explore/action/pia-entanglemen... [2] http://www.ru.nl/hfml/research/levitation/diamagnetic/#Whyfrogs http://www.ru.nl/hfml/research/levitation/diamagnetic/#Whyfr... </rant>
- Practicality 11y ago
  While I applaud your use of citations, do you have another one for cells being able to communicate through glass? That one seems very interesting.
  - kaybe 11y ago
    Sure, lmgtfy: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660427/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660427/ which is a study from 2009 on the phenomenon.
brechmos 11y ago
Agreed. I have been scanned around 1,500 hours over the years and I have not had any ill effects (at this point). And that is 1.5T, 3T and 7T MRI scanners
- relkor 11y ago
  I am curious as to why you have been scanned so many hours over (?) years. How was that funded? Did you learn anything especially interesting other than no ill effects?
ihnorton 11y ago
There can be one effect during diffusion-weighted scanning, which is muscle twitching due to induced depolarization when the gradients are ramped hard. I've had that happen a few times and it was a fairly weird sensation, but not discomforting enough for me to stop the scan. No long-term issues that I'm aware of though.
- ska 11y ago
  This is called peripheral nerve stimulation (PNS), and isn't specific to EPI (e.g diffusion scans). This That's fair though, I really should have been more specific: You can certainly harm a human being with the piece of machinery known as an MR scanner. Much more so than just PNS, you are dumping energy into the body via RF, so there is a specific absorption rate (SAR) limit applied to avoid going into ranges that will damage tissue. What I was refering to was limited only to the effect of exposure to fixed magnetic fields in an MR, and gradients and RF coils as they are constrained for clinical use.
- russpoldrack 11y ago
  I had peripheral nerve stimulation nearly every time I did the diffusion weighted scans, but for me too it wasn't bad enough to stop the scan

tormeh 11y ago

Almost all people curious about the brain, especially neuroscientists, experiment (ha!) with drugs. I won't assume MRI is safe, but cocaine isn't safe either. That's just my anecdotally supported prejudice.