The Leeds Teaching Hospitals NHS Trust


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An X-ray is a safe and painless procedure that's often used to produce images of the inside of the body.

X-rays can also be used to examine organs and identify problems. For example, an X-ray can highlight a lung infection, such as pneumonia.

They are also often used by surgeons during therapeutic procedures, such as a coronary angioplasty, to help guide equipment to the area being treated.

How X-rays work

X-rays are a type of radiation. They're similar sources of energy to light. 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 called photons are absorbed at different rates. This pattern shows up on the X-ray images.

The parts of your body made up of dense material, such as bone, show up as clear white areas on an X-ray image. The softer parts, 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. Some specialist radiographers are also trained to make a diagnosis from the examination.

During an X-ray, you'll 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 an imaging plate.

The X-ray will last for a fraction of a second. As the X-rays hit the imaging plate, the plate will capture a snapshot of the image.

The image will then be transferred to a computer so that a radiologist or radiographer can study them and produce a report. Radiologists are doctors who are specially trained to carry out examinations and interpret medical images, such as X-rays and CT scans.


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.


People are often concerned about being exposed to radiation during an X-ray. However, everyone is exposed to sources of natural radiation throughout their life.

Natural radiation is sometimes known as background radiation. Sources of background radiation include:

  • radon – a naturally occurring radioactive gas found in low levels in the atmosphere.
  • cosmic rays – a type of radiation that originates from space (from the sun and stars).
  • the earth – soil and rocks contain various radioactive materials that have been present since the earth was formed; these contribute to our exposure, as do building materials made from soil, rocks and stones.
  • food and water – for example, nuts, bananas, red meat and potatoes all contain tiny traces of radiation.
Cancer Risk

Being exposed to X-rays carries a theoretical risk of triggering cancer at a later date, as does exposure to background radiation.

However, this risk is very low. For example, the Health Protection Agency (HPA) has calculated that:

  • an X-ray of your chest, teeth, arms or feet is the equivalent of a few days' worth of background radiation, and has a less than 1 in 1,000,000 chance of causing cancer.
  • an X-ray of your skull or neck is the equivalent of a few weeks' worth of background radiation, and has a 1 in 100,000-1,000,000 chance of causing cancer.
  • an X-ray of your breasts (mammogram), hip, spine, abdomen or pelvis is the equivalent of a few months' to a year's worth of background radiation, and has a 1 in 10,000-100,000 chance of causing cancer.  It's important to put the risk of developing cancer from X-rays into perspective. More than one in three people in the UK will develop some form of cancer during their lifetime.

Your risk of developing cancer depends on many factors, including your age, lifestyle and genetic make-up.