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Imaging explained

Imaging plays an important role in modern medicine. Modern imaging techniques – including X-rays, ultrasound, CT scans and MRI – can show structures inside your body in great detail. 

6 min read

What is imaging?

Imaging is a range of tests used to create images of parts of the body. These can help:

  • screen for possible health conditions before symptoms appear
  • diagnose the likely cause of existing symptoms
  • monitor health conditions that have been diagnosed, or the effects of treatment for them.

Imaging is also called radiology. Doctors who specialise in imaging are called radiologists. 

There are many different types of imaging, such as X-rays, CT scan (computed tomography scan), MRI (magnetic resonance imaging) and ultrasound. Each imaging type uses a different technology to create an image. 

This increasing range of imaging types provides health professionals with many options for showing what is happening inside your body.

Radiology technicians or imaging technologists are health professionals who are trained to use specific imaging types, such as radiographers for X-rays or sonographers for ultrasound imaging.

Is imaging the best option for me?

Like any medical procedure or treatment, imaging should be chosen to suit your individual needs. This means it shouldn’t be used routinely when you see a health professional.

For example, the first and most important step when making an accurate diagnosis of an injury is for your health professional to take your medical history and perform a physical examination. Imaging tests can help with a diagnosis, but they don’t replace this step.

Each decision involves weighing up the benefits and risks of having an imaging test.

Early detection of problemExposure to radiation
Accurate diagnosisIncidental findings leading to possibly unnecessary testing or treatment
Ongoing monitoringEmotional stress
Contribution to choice of effective treatmentCost
Improved management of condition 

In the end, an imaging test should only be performed if it’s likely to help with diagnosis and improve the management of your health condition or injury.


  1. Government of Western Australia. Diagnostic Imaging Pathways. About imaging: About guidance. [Online] (accessed 30 October 2016).
  2. Choosing Wisely Australia. What is Choosing Wisely Australia? [Online] (accessed 30 October 2016).

What are my imaging choices?

Common types of imaging include:

  • X-rays
  • CT scan (computed tomography scan)
  • MRI (magnetic resonance imaging)
  • ultrasound
  • nuclear medicine imaging, including positron-emission tomography (PET)

Each one uses a specific technology. They differ in how well they show what is happening in certain body tissues. For example, X-rays are often best at finding a break of a bone, whereas an MRI may be better for identifying a ligament injury. When your health professional decides what kind of imaging to recommend to you, they take the different strengths of each imaging type into account. 

No type of imaging is always better. Each has different potential advantages and disadvantages, including exposure to radiation with some types of imaging. Your health professional should discuss with you which type of imaging is most appropriate for you.

How do the imaging choices compare?

Here are different types of imaging - X-rays, CT scans, nuclear medicine imaging including positron-emission tomography (PET), MRI and ultrasound – with explanations on how they’re used, and some advantages and disadvantages of each one.

Imaging typeAdvantages & disadvantages
Plain X-ray

Uses X-rays to show images of bones, some tumours and other dense matter

  • Quick, non-invasive and painless
  • Can help diagnose various diseases and injuries, including broken bones, some cancers and infections

  • Very small increased risk of cancer in future from exposure to ionising radiation (X-rays). Risk is greater for children
Computed tomography (CT scans)

Uses multiple X-rays to produce cross-sectional layers that show detailed images inside the body, including bones, organs, tissues, and tumours

  • Quick and painless
  • Can help diagnose and guide treatment for a wider range of conditions than plain X-ray
  • Can detect or exclude the presence of more serious problems
  • Can be used to check if a previously treated disease has recurred

  • Small increased risk of cancer in future from exposure to ionising radiation (X-rays). Risk is greater for children
  • Uses higher doses of radiation than plain X-ray, so the risks (while still small) are generally greater than for other imaging types
  • Injection of a contrast medium (dye) can cause kidney problems or result in allergic or injection-site reactions in some people
  • Some procedures require anaesthesia
Nuclear medicine imaging including positron-emission tomography (PET)

Involves injecting, inhaling or swallowing a radioactive 'tracer'. The gamma-rays emitted by this material are used by the scanner to show images of bones and organs

  • Usually painless
  • Can help diagnose, treat, or predict the outcome for a wide range of conditions
  • Unlike most other imaging types, can show how different parts of the body are working and can detect problems much earlier
  • Can check how far a cancer has spread and how well treatment is working

  • Involves exposure to ionising radiation (gamma-rays)
  • Radioactive material may cause allergic or injection-site reactions in some people
  • PET scanners cause some people to feel claustrophobic, which may mean sedation is required
Magnetic resonance imaging (MRI)

Uses magnetic fields and radio waves to show detailed images of organs, soft tissues, bones, ligaments and cartilage

  • Usually non-invasive and painless
  • Uses no ionising radiation
  • Can help diagnose and guide treatment for a wide range of conditions
  • Can provide similar information to CT in some types of investigations

  • Can be a lengthy and noisy procedure
  • Slight movement can ruin the image, requiring retesting
  • Can make some people feel claustrophobic
  • Sedation or anaesthesia may be required for young children or others who can't remain still
  • Injection of a contrast medium (dye) if needed can cause kidney problems or result in allergic or injection-site reactions in some people
  • Can't be undertaken in some situations (e.g. when a heart pacemaker is present)

Uses high-frequency sound waves to produce moving images onto a screen of the inside of the body, including organs, soft tissues, bones, and an unborn baby

  • Usually non-invasive, safe and relatively painless
  • Uses no ionising radiation
  • Does not usually require injection of a contrast medium (dye)
  • Can help diagnose a range of conditions in different parts of the body, such as the abdomen, pelvis, blood vessels, breast, kidneys, muscles, bones and joints
  • Can be used to check on the health of a baby during pregnancy

  • Quality and interpretation of the image highly depends on the skill of the person doing the scan
  • Other factors can affect image quality, including the presence of air and calcified areas in the body (e.g. bones, plaques and hardened arteries), and a person's body size
  • Use of a special probe (e.g. for the oesophagus, rectum or vagina) is required in some ultrasounds
  • Special preparations may be required before a procedure (e.g. fasting or a full bladder)

How should I talk to a health professional about imaging?

It's important to be well informed before making a decision about having an imaging test.

You need to know your imaging choices, find out the advantages and disadvantages of each type of imaging and talk to your health professional about any questions or concerns you may have.

Ask these 5 questions about any imaging test.

  • Do I really need this test?
    A test should enable you and your health professional to detect or determine a problem or monitor its progress, and/or decide on the most effective and safest treatment.
  • What are the risks?
    Examples include side effects and getting results called incidental findings that aren’t related to your problem but may lead to unnecessary tests or treatments.
  • Are there simpler, safer options?
    For example, a medical history and physical examination may be just as accurate as an imaging test, or another type of imaging that doesn’t involve radiation may be safest.
  • What happens if I don't do anything?
    Ask whether your condition could get worse – or better – if you don’t have the imaging test right away.

  • What are the costs?
    Costs can be financial, emotional or just the waste of your time. Where there is a cost to the community, perhaps there’s a cheaper alternative.


Choosing Wisely Australia. 5 questions to ask your doctor or other healthcare provider. [Online] (accessed 30 October 2016).

More information

Choosing Wisely Australia

Choosing Wisely Australia is an initiative that brings the community together to start important conversations among healthcare providers and consumers. These conversations aim to improve the quality of healthcare through reconsidering tests, treatments and procedures where evidence shows they provide no benefit or, in some cases, lead to harm.

Facilitated by NPS MedicineWise, it is led by a large cross-section of colleges, societies and associations that have identified practices that warrant scrutiny, and by examining the evidence and drawing on the expert opinion of their members, have developed lists of recommendations.

Three colleges and associations make recommendations on the use of X-rays for ankle injuries:


Produced by Australian and New Zealand radiologists and other health professionals about imaging (radiology) tests and procedures. It contains information for health consumers and treating health professionals, endorsed by the Royal Australian and New Zealand College of Radiologists (RANZCR).


Public information resource for patients about imaging (radiology) tests developed by physicians from the Radiological Society of North America and the American College of Radiology.

Better Health Channel

Fully funded by the Victorian Government, this website provides health and medical information about imaging and related health conditions and injuries that is quality assured and reliable, up to date, locally relevant and easy to understand.


Jointly funded by the Australian Federal Government and the governments of the Australian Capital Territory, New South Wales, Northern Territory, South Australia, Tasmania, and Western Australia, this website provides services, including high quality information about imaging and related health conditions and injuries, by acting as a portal to reliable and reputable sources.  

6 min read