What TECHNOLOGY fact made you think "NO, REALLY"?

by Ollie Tizzard on Quora

MRI Scanners. When I read how they work I literally put my tea down and sloshed it everywhere and said “it does what?!” out loud.

I long thought Magnetic Resonance Imaging scanners worked along similar lines to X-Rays or CT scans and used projected radiation.

Nuh-uh. (standby for some layman-speak)

We human meatbags are about 70% water. It’s a substrate in all our tissues.

Water is Hydrogen and Oxygen. Two atoms of the first and one the latter. Our Hydrogen atoms are one proton and one electron. We’re not so interested in those.

Our body’s hydrogen protons are usually all buzzing around like a classroom full of unruly kids with a timid supply teacher.

Their magnetic fields are all over the place and thus we, as humans, are generally not magnetic.

* Enter enormous electromagnetic stargate-bed *

Inside that thing is, among other things, a series of immensely powerful electromagnets.

The primary magnet, literally makes all of our body's hydrogen protons sit up, pay attention, and align themselves with the magnetic field.

It wraps you up in a forcefield and plays with the very atoms of your being.

The “kids” (protons) now sit round and face teacher, fidgeting in their seats in anticipation, and you are now magnetic.

The magnetic field direction is “longitudinal”, or from your feet to your head.

…Except for a few protons. Some are at higher energy states and resist aligning themselves to the field, and face the opposite direction (or what is called, being “anti-parallel”)

What happens next is a radio frequency generator sends a radio pulse that exactly matches the spin frequency of the protons, or resonance.

This gives a little energy boost to the protons that are aligned in the direction of the magnetic field, until 50 percent of the protons are flipped with the magnetic field, and 50 percent aren't. The magnetic fields cancel each other out.

The protons themselves also now spin together at the same pace and are all at the same points in their orbit or are in phase

protons actually spin around an axis a little like a spinning top, which is known as precession. Imagine our protons are the tip of this spinning top and the line of the magnetic field is the bottom point on which it spins around)

As the protons are all spinning in a common direction, this creates another magnetic field, and in turn this movement generates a small electrical current in antennae which can be measured.

The RF frequency is then shut off. The protons return to their previous state, i.e. half facing their respective directions in the magnetic field, and now following their own points of orbit, no longer in phase.

The protons “relax” back into this state, and the difference between them switching from one state back to the first is what is measured.

Different tissues, like muscle or fat, have different water densities and electrical resistance, so the time taken for the protons to shift will differ, so we can contrast different tissues very clearly.

The signatures picked up by the machine of all this magnetic jiggery-pokery are calculated into images by some algorithmic magic, and is astonishingly detailed.

MRIs use the above process in contrast to the absorption of radiation such as in X-Rays and CT scans, and as such produce more detailed images of soft tissues and bodily structures in general.

In my mind it may as well be straight out of Star Trek.

***I've been without sensible Internet for a bit: 10k upvotes, wtf?! Humble thanks! ***