Looking inside the Human Body: How MRI works

How does an MRI scanner work?

hallux - radiology

Body has accidentally swallowed Professor Hallux’s keys to the fridge! Whoops!

Now Body isn’t very well and he’s in lots of pain! The only thing is, they need to know exactly where the keys are in Body’s body, and they need some cool gadgets to help. Professor Hallux, Nurse Nanobot and Body have made their way to the Imaging department at their local hospital.

There are different types of radiology technology to see inside your body when you’re feeling poorly. There’s one type of radiology that uses powerful magnets to see inside our bodies. It’s called MRI!


MRI stands for Magnetic Resonance Imaging. Footballers with muscle injuries have these types of scan all the time.

  • They’re also used for spine and brain injuries too because they’re very complex parts of the body and MRIs give the most detail of all.


MRI uses VERY strong magnets and radio frequency pulses to generate signals from the body. Every hydrogen atom in your body acts like a tiny magnet and an MRI scanner uses a huge magnet and radiowaves to generate signals from the hydrogen ions. The signals are detected by a radio antenna within the scanner and are processed by a computer to create really detailed images of the inside of your body.

Now, as Body has a lot of metal inside him, having an MRI scan might not work out too well!



The magnets inside the scanner are so strong that they would pull any magnetic objects towards the machinery! Even a bucket or a metal bin in the same room would fly like a missile onto the big magnets. People have been injured by objects flying around like that! To keep everyone safe, patients and staff, no metallic or electronic things are allowed in the room.

  • You have to take off all your jewellery, watches and belts.
  • You will also usually be asked to change into a gown. This helps to make sure that there’s nothing left in your pockets before you enter the MRI room.
  • Even make-up and hairspray aren’t allowed because they might have tiny bits of metal in them, and if they get hot they might interfere with the equipment.

Before you go for a MRI scan, you might have to fast for a little bit – that means not having anything to eat for a few hours.  This is to ensure that no food in the way of the pictures.

The MRI scanner is generally shaped like a VERY fat doughnut with a tunnel passing through it!

  • There’s a table on which you lie which slides into the tunnel. Don’t worry, both ends of the tunnel are open and don’t close, and the tunnel has lights in it and sometimes a mirror.
  • Before you go into the tunnel, some wires and monitor pads might be stuck to your body or sometimes some wires are wrapped around part of your body.


The radiographer will make them as comfy as possible. An important thing to know is that the MRI scanner is very noisy whilst it’s scanning, so you’ll be given earplugs or headphones to reduce the noise to a nice safe level.

  • MRI scanners usually have CD and DVD players so you can watch a movie or listen to some music whilst you’re being scanned.

You have to stay very still for your scan, sometimes for a few minutes, other times for longer. You might even have to hold your breath too for a few seconds. But don’t worry if you get a really bad tickle or are feeling worried or sick, you can press a buzzer and talk to the radiographer or take a break!

It might sound complicated but radiographers are trained to explain it all and make you feel super comfortable about what’s going on. And MRIs are very safe – they don’t use X-ray radiation so can be used on young children and even on ladies with babies inside their tummies too.

How much radiation?

  • As MRI doesn’t use X-ray radiation, it has no known long-term harmful effects. Avoiding the need for exposure to X-rays is a big benefit for children, especially if they need more scans to follow up their illness.
  • The danger from the MRI is with metal objects around the magnetic fields. Metal objects can move, as well as get hot, and electrical currents can be produced and lead to malfunction of a device, so radiographers are very strict about making sure you have no metal hidden on you!.

Click here for a virtual tour of an Imaging Department!



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