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An x-ray is an imaging test that uses small doses of radiation. The term “x-ray” is used to describe the rays of radiation, the test and the images they create of internal organs and structures of the body.

An x-ray is also called a radiograph or radiogram.

Examples of basic x-rays
Type of x-rayWhat is studied

chest x-ray

chest, lungs, heart and surrounding bones

bone x-ray




Some x-rays use a contrast medium to produce better images. For example, the contrast medium barium sulphate is used to make organs and structures show up clearly on the x-ray image of an upper gastrointestinal (GI) series.

Why an x-ray is done

An x-ray may be done to:

  • follow up suspicious findings from a physical examination or laboratory test
  • diagnose cancer
    • X-rays can help doctors assess a tumour’s size and determine the stage (find out how far the cancer has spread and if it is present in other organs and tissues).
  • compare the tumour before (baseline), during and after treatment
  • screen for certain types of cancer (in some cases)

How an x-ray is done

An x-ray is usually done as an outpatient procedure in the x-ray (radiology) department of a hospital or clinic. The test usually takes 10–15 minutes, but may take longer.

  • It is important for women to tell the x-ray technologist or radiologist if they are pregnant or think they may be pregnant before having any type of x-ray. If a contrast medium will be used, it is important for women to tell the x-ray technologist or radiologist if they are breast-feeding.
  • The person will be asked to remove clothing, jewellery and other objects that will be in the x-ray field and may interfere with the quality of the x-ray.
  • No preparation is usually needed for a basic x-ray without contrast medium.
  • Special preparation may be needed for an x-ray with contrast medium.
    • The person may be ask to:
      • not eat or drink anything for a certain number of hours before the test
      • take a laxative
      • have an enema
    • The contrast medium may be given:
      • orally
      • though the rectum (enema)
      • by injection
      • through a thin tube (catheter) inserted into different body tissue
  • Depending on the area being studied, the person will lie on an x-ray table or will stand or sit in front of an x-ray machine.
  • A lead apron may be placed over the pelvic area to protect reproductive organs.
  • The x-ray machine is positioned over the area to be imaged.
  • When the x-ray is taken, people must stay very still and may be asked to hold their breath.
  • The x-ray technologist leaves the room or goes behind a shield while the x-ray is taken.
  • A small beep or buzz will be heard when the x-ray is finished.
  • The person may be asked to change position so that x-rays can be taken from different angles.
  • The person may be asked to wait until the x-rays are developed and the staff is sure that the image is clear.

Potential side effects

X-rays involve low levels of ionizing radiation, which has the potential to cause cancer and other defects. The number and complexity of x-rays needed to diagnose and determine the extent of a disease can vary. Even with multiple and repeated x-rays, the total dose of radiation and the associated risk is small. X-rays are strictly monitored and controlled to make sure they use the smallest amount of radiation possible. The expected benefits of the x-rays must always outweigh any possible risk for the x-rays to be done.

On rare occasions, the contrast medium may cause an allergic reaction.

What the results mean

The shadow-like images on an x-ray are the result of radiation being absorbed differently by different body tissues.

  • Bones absorb the most radiation and appear white.
  • Fat and other soft tissues absorb less radiation and appear in various shades of grey.
  • Air absorbs the least radiation and structures filled with air (such as the lungs) appear black.

X-rays can be used to look for and examine some types of tumours.

  • Most tumours are soft tissue and do not show up well on x-ray.
  • Lung tumours show up well because of the air in the lungs around them.
  • An x-ray cannot always tell the difference between a cancerous (malignant) tumour and a non-cancerous (benign) tumour.

What happens if a change or abnormality is found

The doctor will decide whether further tests, procedures, follow-up care or additional treatment are needed.

Special considerations for children

Being prepared for a test or procedure can reduce anxiety, increase cooperation and help the child develop coping skills. Parents and caregivers can help prepare children by explaining to them what will happen, including what they will see, feel and hear during the test.

  • The child will probably be alone in the room.
  • An x-ray is completely painless.
  • The child will have to stay still for a few seconds while the x-ray is taken.
  • If a contrast medium is used, the child may have an intravenous injection, enema or catheter, depending on the type of study being done.

The preparation you can provide for an x-ray depends on the age and experience of the child. See the following for more age-specific information on helping children cope with tests and treatment.

contrast medium

A substance used in some diagnostic procedures to help parts of the body show up better on x-rays or other imaging tests.

In most cases, contrast medium is injected into or around the structure to be examined.

Also called contrast dye or contrast agent.


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