How does an MRI work?


I don’t even know the right kind of flair for this question- tech? physics? biology?


eta: thank you everyone! This is all very helpful. I was in the big MRI tube yesterday and had no idea how the technology actually worked. So cool!

In: 7

MRIs work by using very strong magnetic fields to manipulate the protons in your body, and based on how the electrons respond to the magnetic field we can differentiate between different substances. This is why MRIs can do more than X-rays, which can only differentiate between bone and not bone (for the most part): an MRI can tell the difference between fat and water and other different fluids. I’d highly recommend checking out [This Video]( from Real Engineering that does a fabulous job explaining how they work!

[MRI stands for]( “magnetic resonance imaging”, and to understand why we use that tech for medicine, you have to understand a bit of physics.

Everything is a tiny bit magnetic. Iron is *especially* magnetic, but everything’s a little bit magnetic, so if you have a powerful enough magnet, it will “push” a little bit against everything, even the insides of your body. So an MRI machine starts by making an extremely strong **magnetic** field, and literally magnetizing your body. That’s the “magnetic” part.

The “push” of the magnetic field causes all the hydrogen atoms in your body to align in the same direction, like magnets lining up with one another (because that’s what they are, everything is a tiny bit magnetic).

And this is where the “**resonance**” part comes into play. The second step of an MRI machine is that it sends short pulses of a different electromagnetic field, pushing the hydrogen atoms into a slightly different direction. When that second pulse ends, the hydrogen atoms snap back into place, sending out a tiny electromagnetic pulse back of their own.

That feedback information, all the tiny electromagnetic pulses from all the hydrogen atoms snapping back into place… that’s what the machine uses to construct an **image** of the inside of your body.

The link above is to Khan Academy for a deeper overview if you want.

Physics, biology, chemistry, and engineering. And a whole lot of math. has good results but I’ll give a quick rundown.

All medical imaging effectively is sending energy at the subject and seeing what goes through or back. X-ray and CT use X-ray and a detector on the opposite side and you catch where the X-ray energy passed through to find things that are denser.

MRI puts the subject in a magnetic field. Hydrogen atoms line up inside a magnetic field. Radio energy is ‘shined’ on the subject, and the machine ‘listens’ to what it hears back. The computers attached then take the signal and construct an image from that.

Now that your question has been answered, I wanted to point out that you weren’t sure what “flair” to use for the post. One of the MRI modes is called T2 Flair, so you just made an awesome joke haha.