Hacker News Reader

Hacker News

Comment by kick_in_the_dor | Hacker News Reader

Full thread

kick_in_the_dor

Is it bad for the human brain to receive that much radiation?

(I have no idea if magnetic field == radiation, I was just told from my ENT that doing too many CT scans can be risky)

View on HN

I didn't really know this, but a Computed Tomography scan uses X-rays.

https://en.wikipedia.org/wiki/CT_scan

An MRI is just a great big magnet (generated by a superconductor that is held at low temperatures by liquid helium).

From the safety section of the wiki: "Since MRI does not use any ionizing radiation, its use is generally favored in preference to CT when either modality could yield the same information... MRI uses powerful magnets and can therefore cause magnetic materials to move at great speeds, posing a projectile risk, and may cause [extremely rare, perhaps fatal] accidents."

https://en.wikipedia.org/wiki/Magnetic_resonance_imaging

If you've had a PET scan, then you've been exposed to antimatter (anti-electrons) for Positron Emission Tomography (which ends up as gamma ray radiation).

https://en.wikipedia.org/wiki/Positron_emission_tomography

A magnetic field is not radiation. The changing RF fields used are, but they're not ionizing radiation (the dangerous kind) like that found in CT scans. The radiation used in MRIs should not be able to induce any changes to the molecular structure of your body, but RF burns can still be a risk. (Clothing and even tattoo ink can exacerbate this, fascinating!) The biggest risk seems to be being bonked by loose medical equipment, but I don't think that's what you were asking about.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2705217/

There is a theory that there could be unexplored effects of RF exposure. For example, we can see that glucose metabolism increases in brain tissue exposed to RF. That could be the end of it, or there could be consequences to that under the right conditions. We don't know yet.

This - burns are actually more common than projectile injuries but a well run facility should have very few or zero of either.

CT scans irradiate you, MRIs don't really. Just don't have any metal in you.

More correctly, MRI doesn't use ionizing radiation. They definitely irradiate you with high power RF.

Mental in your body is nearly always fine.

*metal.

Is not radiation. It’s just strong magnetic fields.

Still the question remains, are they dangerous?

I guess some materials in the body have some response to magnetic fields

not at all whatsoever. however if you have gadolinium injected for contrast some people have problems with that. but the magnetic field itself doesn't affect you negatively on its own

Is there a field strength at which the iron in your blood would start to become a problem?

This is probably an adequate answer to that:

https://www.reddit.com/r/AskPhysics/comments/3w03pj/comment/...

Some experiments with magnet, water, blood etc.

https://www.youtube.com/watch?v=E-yHv91Y_oI

We don't have any evidence they are dangerous. There are some phenomenon like magnetophosenes. You could also look up what a magnetar would theoretically do to a body, but nobody is getting close to one of them anytime soon.

Very strong constant magnetic fields don't seem to be dangerous (at least at the kind of levels MRI machines work at, which are within an order of magnitude of the strongest magnets on the planet). A very rapidly changing strong magnetic field can be dangerous, because it induces currents in your body, like in your nerves. There are safety limits (very conservatively set) in MRI machines on how quickly they adjust magnetic fields, as if they were to really go for it there's a risk of heart problems (in the moment, it's not like CT scans where more exposure means more risk later in life).

Reply on news.ycombinator.com