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Looking inside the Human Body: The Science Behind Radiation

How do we see inside the human body?

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Radiation, which in simple terms is ‘the transfer of energy from one place to another’ is very common, you find it everywhere in nature! There are all sort of useful types. If you’ve ever been on holiday, you’d have got your bags scanned to see if you have anything you shouldn’t.

First of all, there’s something called background radiation. It’s radiation that’s found in soil, in our air and water, and in us. Because it occurs naturally, it’s in the food we eat, the water we drink, the air we breathe and the materials we build our homes with. You also get cosmic radiation from the sun, which can be higher when flying in an aeroplane as you get less protection from the atmosphere the higher you are!

And then there’s man-made radiation like medical X-rays which have helped us see inside things for over a hundred years! So you can see that radiation is just part of our universe, and can be very helpful. Some radiation is good for you, and some is bad. Radiation has to be managed very carefully because if you do get too much, there’s a very real danger that you will feel very poorly.

chest-x-rayAs with many of mankind’s monumental discoveries, X-ray technology was invented completely by accident. In 1895, a German physicist named Wilhelm Roentgen made the discovery while experimenting with electron beams in a gas discharge tube. He noticed that a fluorescent screen started to glow when the electron beam was turned on. Now whilst this shouldn’t be surprising – after all, fluorescent materials normally glow in reaction to electromagnetic radiation – Roentgen’s tube was surrounded by heavy black cardboard. He assumed this would have blocked most of the radiation.

X-rays are a wonderful addition to the world of medicine – they let doctors peer inside a patient without surgery, which is much easier and safer than opening a patient up.

But X-rays can also be harmful. In the early days of X-ray science, a lot of doctors would expose patients and themselves to the beams for long periods of time. Eventually, doctors and patients started developing radiation sickness, and people sussed out that something was wrong.

X-rays are very similar source of energy to a light. However, light is absorbed by your skin and mostly stops. A bit like when you throw a water balloon at a wall. But X-rays pass through the human body and out the other side. Imagine that water balloon passing all the way through the wall and out the other side.

As X-rays pass through the body, tiny particles of energy called photons get soaked up at different rates by the atoms in our bodies. Normal light can’t change these atoms much but the protons in X-rays can bash into the atoms and cause damage. That can make you sick because the damage can mess up your body’s DNA, that’s like the instruction book that tells each cell how to grow. And it’s not much use if it’s full of gobbledegook! And to make matters worse, those damaged cells become charged up in a way that make them damage other cells around them too, so it’s a bit like a chain reaction.


Some of the waste from power stations which make electricity for us has very strong radiation which would damage cells in our bodies very quickly. But the waste is very carefully stored so that it can’t harm anyone.

There are lots of things in the world which can be harmful and helpful – managing them safely is what matters. If you think about it, even fire can be dangerous but it would be a chilly world without it!


And that’s why the radiologists and radiographers here are so highly trained! They know how to use just the right amount of radiation to get a good look inside, whilst keeping you safe. In fact, for children they’ll try and use ultrasound wherever possible to avoid radiation exposure. And a great deal of X-rays only use the same amount of radiation as you’d get just hanging out on earth for a few days.

Click here for a virtual tour of a real imaging department!



Click on a topic below to explore more radiology!

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Professor Hallux: Looking inside the Human Body!

Find out what's Inside the Human Body with Professor Hallux

More From Professor Hallux: Looking inside the Human Body!