X-ray is a safe and painless procedure often used to produce images of the inside of the body.
It is a very effective way of looking at fractured bones, such as a broken arm or wrist.
An X-ray can also be used to examine organs and identify problems. For example, an X-ray will show up an infection in your lungs, such as pneumonia.
X-rays are also often used during therapeutic procedures, such as a coronary angioplasty, to help the surgeon guide equipment to the area being treated.
Read more about when X-ray is used.
How X-rays work
X-rays are a type of radiation. Light and X-rays are similar sources of energy. However, light has a much lower frequency than X-rays and is absorbed by your skin. X-rays have a higher frequency and pass through the human body.
As X-rays pass through the body, energy particles in them (called photons) are absorbed at different rates. This pattern shows up on the X-ray images.
The parts of your body that are made up of dense material, such as your bones, show up as clear white areas on an X-ray image.
The parts of your body that are made of softer material, such as your heart and lungs, show up as darker areas.
Having an X-ray
X-rays are carried out by radiographers who are healthcare professionals trained to use imaging technology, including X-ray machines, computerised tomography (CT) scanners and ultrasound scanners.
During an X-ray you will be asked to lie on a table or stand against a flat surface so that the part of your body being examined is positioned between the X-ray machine and a photographic plate.
The X-ray will last for a fraction of a second. As the X-rays hit the photographic plate, the plate captures a snapshot of the image.
The resulting image will be transferred to a computer so it can be studied on a screen and printed out if necessary.
Read more about how an X-ray is taken.
Safety
Exposure to high levels of radiation can be very harmful. However, the X-rays used for medical purposes are safe because the dose of radiation is very small.
The strength of radiation in relation to long-term risk is measured using units called millisieverts (mSv). Some examples of typical exposures are:
- chest X-ray: 0.02 mSv
- a year’s worth of medical tests: 0.4 mSv
- average annual exposure to natural radiation: 2.2 mSv
In the UK, 20 mSv is the limit that someone who works with radiation is allowed to be exposed to in any given year. Most workers receive considerably less than this.
Read more about the risks of X-rays.
