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Imaging is the creation of pictures of areas inside the body that could not otherwise be seen. There are many different technologies used to create images. Images are created by the way different tissues react to x-rays, radioactive particles, sound waves or magnetic fields. Sometimes a contrast medium is used to create a better picture.

Common imaging tests
Type of imaging testHow images are producedExamples

x-ray (radiograph)

  • x-rays (with or without contrast medium)
  • mammogram
  • barium enema
  • sound waves
  • breast ultrasound
  • pelvic ultrasound

nuclear medicine imaging studies

  • radioactive isotopes or radiopharmaceuticals
  • bone scan
  • positron emission tomography (PET) scan
  • x-rays (with or without contrast medium)
  • CT scan of the chest
  • CT scan of abdomen
  • magnetic fields (with or without contrast medium)
  • MRI of the brain
  • MRI of the spine

Why an imaging test is done

Imaging is done to:

  • check the structure and function of body tissues and organs
  • detect abnormalities caused by various diseases, including cancer
  • help make a diagnosis of cancer
  • guide doctors to an abnormality or suspected tumour so they can take a biopsy sample  or remove the abnormal tissue
  • determine the stage (how far cancer has spread and if it is present in nearby organs or tissues)
  • help plan cancer treatment
  • find out if cancer treatment is working (if the tumour has increased or decreased in size)
  • check if cancer has come back (has recurred) after treatment

How an imaging test is done

Each test uses a different technology and imaging machine. Depending on the type of imaging test, it may be done in a doctor’s office, clinic, imaging centre or hospital. Some tests require special preparation.

  • Sometimes a contrast medium is given before the test:
    • orally
    • by enema (a procedure used to inject a liquid into the colon and rectum through the anus)
    • intravenously (injected into a vein in the hand or arm)

The images are captured on x-ray film or a computer. They are read and interpreted by a doctor who specializes in imaging techniques (a radiologist) or a nuclear medicine doctor.

What the results mean

An imaging test can show:

  • a change in the structure of an organ that could be due to injury or disease
  • a mass, lesion (an area of abnormal tissue) or area of increased activity that could be a tumour or something caused by another disease
  • the spread of cancer to other organs
  • a decrease or increase in the size of a tumour (depending on how well treatment is working)

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.

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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