Choosing the right type of tests to have can be confusing for patients and you should be guided by your health care practitioner. However, the following information may be useful for you and give you a better understanding of different types of tests.
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.
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. 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.
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.
The benefits include early detection of the problem, accurate diagnosis, can contribute to effective choice of treatment and management of a problem and allows ongoing monitoring.
The risks involved are exposure to radiation, incidental findings which can lead to further unnecessary tests or treatment, cost and emotional stress.
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.
How do the imaging choices compare? Take a look at this helpful guide created by NPS Medicine wise (2016):
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)
(NPS Medicine Wise, Choosing Wisely Australia: Imaging explained, 2016, nps.org.au)