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Comment by peter303 | Hacker News Reader

Something called Transcranial Magnetic Stimulation alters brain activity at about one Tesla (10,000x earth's field). TMS has been shown to induce euphoria, amnesia, and relieve depression. Unclear what stronger magnetic fields could do. A ten Tesla magnet can levitate a small animal.

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I work in this sector, and what you say is correct, however it is important to note that in TMS the fields are pulsed over millisecond time intervals. In doing so they can induce an electric field which can cause neurons to fire. The time varience is crucial. A 3T static field from the magnet of an MR scanner is far less dangerous than a 1T field pulsed in the vicinity of your brain. That is providing that there aren't any ferromagnetic objects close to the MR scanner!

Radiologist here. We regularly image patients in 3T MRI scanners. As long as they don't have certain metal surgical implants, a pacemaker, or metallic foreign bodies, there is no problem.

Some institutions have research magnets up to 7T: http://www.healthcare.philips.com/main/products/mri/research...

My research institute has a 11.7T (for small animals).

Although I must say, using MRI, even such a powerful one, for research is not as useful or cool as you'd expect since it takes so long to do one scan.

> there is no problem

We are just beginning to investigative the post operative changes from anaesthesia in adults [1]. Can we be sure that there is no post MRI changes ?

While I'm not suggesting there is any cause for alarm I don't think we should dismiss the possibility out of hand.

[1] http://www.scientificamerican.com/article/hidden-dangers-of-...

tattoos can be a problem, right?

Yes, certain inks contain enough metal to cause significant tissue heating.

http://www.youtube.com/watch?v=A1vyB-O5i6E Not sure if the video is trustworthy, but here's a 97 paper saying 16T can lift a frog http://iopscience.iop.org/0143-0807/18/4/012

http://www.critic.co.nz/columns/article/3703/science-bitches...

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