Question: How do you do an MRI scan?

Cameron Manning answered on 10 Dec 2020:

An MRI scan uses very powerful magnets to change the magnetic properties of water molecules in your body. When you are inside the scanner, the water molecules magnetic moment will align in the same direction of the strong magnetic field of the scanner – so the water in your body will all point the same way!
If we then use another smaller magnetic field, we can ‘poke’ the water molecules out of alignment, then they will ‘relax’ back to the direction of the big field.
As the water molecules ‘relax’ they induce a current in a coil, which we interpret as a signal. Putting all the signals together tells us about the quantity and behaviour of water molecules in your body, and gives us an image.

We need really strong magnetic fields to make all this happen, so we use a metal compound called Niobium-Titanium, and cool it down to less than minus 260 degrees celsius, so we can put thouasands of volts through it!