An x-ray is an imaging test that uses small doses of radiation to produce pictures of internal organs and structures of the body.

Some x-rays use a contrast medium to show organs and structures more clearly.

Why an x-ray is done

An x-ray may be done to:

  • follow up suspicious findings from a physical examination or laboratory test
  • find out the size, shape and location of tumours
  • see how far cancer has spread and if it is in other organs and tissues (staging)
  • find out if cancer treatment is working by comparing the size of the tumour before, during and after treatment
  • screen for some types of cancer

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. This means that you don’t stay overnight. The test usually takes 10 to 15 minutes, but it may take longer.

Before you have an x-ray, it is important to tell the x-ray technologist or radiologist if you are pregnant or think you may be pregnant. If a contrast medium will be used, it is important that you tell the x-ray technologist or radiologist if you are breastfeeding.

You don’t usually need to do anything to prepare for a basic x-ray without a contrast medium. If you are having an x-ray with a contrast medium, you may be asked 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:

  • by mouth (orally)
  • by needle into a vein (intravenously)
  • through the rectum (called an enema)
  • through a thin tube (catheter) inserted into different body tissue

You 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. Depending on the area being studied, you will lie on an x-ray table or will stand or sit in front of an x-ray machine. You may have a lead apron placed over your pelvic area to protect your reproductive organs.The x-ray machine is positioned over the area to be imaged.

When the x-ray is taken, you must stay very still and you may be asked to hold your breath. The x-ray technologist leaves the room or goes behind a shield while the x-ray is taken. You will hear a small beep or buzz when the x-ray is finished. You may be asked to change position so that x-rays can be taken from different angles.

Side effects

X-rays use low levels of ionizing radiation. Ionizing radiation is strong enough to damage cells in our bodies and increase the chance of developing cancer. X-rays are strictly monitored and controlled to make sure they use the least possible amount of radiation. Even with multiple and repeated x-rays, the total dose of radiation and the associated risk is small. The benefits of having an x-ray outweigh the risk of exposure to the small amount of radiation received during the scan.

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

What the results mean

The shadow-like images on an x-ray are made from 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 around them in the lungs.

An x-ray cannot always show the difference between a cancerous (malignant) tumour and a non-cancerous (benign) tumour.

What happens if the results are abnormal

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

Special considerations for children

Preparing children before a test or procedure can help lower their anxiety, increase their cooperation and develop their coping skills. This includes explaining to children what will happen during the test, such as what they will see, feel and hear.

Preparing a child for an x-ray depends on the age and experience of the child. Find out more about helping your child cope with tests and treatments.

Expert review and references

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

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