At some point, we’ve all heard of someone having an MRI, a CT or a PET scan.

But when your doctor suggests that you need a medical scan, especially if it is your first one, it can be incredibly daunting.

How does it work? What can it show? Will it hurt?

It’s completely normal to feel anxious, but understanding what is involved can help so we thought we’d take a look at the different types of scans and help answer some of the most common questions people have.

CT/ CAT Scan

What does a CT/CAT Scan stand for? Computerised Tomography scan/ Computerised Axial Tomography scan.

How does it work? It takes cross-sectional images (x-rays) of various parts of the body in 2D. With the assistance of computer processing, the images are stacked together to create a 3D image of the whole body. It is particularly useful for scanning the pelvis, chest and abdomen. Whilst it causes radiation exposure, the Royal Australian and New Zealand College of Radiologists told the ABC there is an estimated 0.04% increase in the risk of developing cancer from it.

What does it scan?

  • Soft tissue, blood vessels, organs, and bones.

What can it reveal to the doctor?

  • Bone and joint problems, like complex fractures.
  • The size and location of tumours.
  • Blood clots, excess fluid or infection.
  • Evidence of cancer, heart disease, emphysema or liver masses.
  • Organ tears and injuries, even bleeding in the brain.

What to expect from a CT Scan: You will lie on a bed that slowly moves through the gantry while the x-ray tube rotates around the patient, shooting narrow beams of x-rays through the body. The doctor may tell you to stop eating and drinking for a period of time before your scan. You may also have to take a contrast agent as a drink, enema or injection, which will mark some tissues or blood vessels more clearly.

MRI Scan  

What does an MRI scan stand for: Magnetic Resonance Imaging scan

How does it work? It is a non-invasive imaging procedure that captures 2D and 3D images of the body using powerful magnets to examine soft tissue. Unlike the x-rays from a CT scan, it does not use radiation.

What does it scan? Soft tissue.

What can it reveal to the doctor?

  • Tumours, including cancer
  • Soft tissue injuries such as damaged ligaments
  • Joint injury or disease
  • Spinal injury or disease
  • Injury or disease of internal organs, including the brain, heart and digestive organs.

What to expect from the MRI scan: You will be asked to remove all metal objects, including wristwatches, keys and jewellery. You will lie on the scanner’s table wearing a cotton gown.  The table will slide into the cylinder. An intercom inside the MRI scanner will allow you to talk with staff. Lie very still, as movement will blur or distort the images. The machine will make loud noises, so the clinician will give you earphones or earplugs to protect your ears. Let the doctor know if you start to feel claustrophobic.


What does a PET/SPECT Scan stand for? Positron Emission Tomography/Single Photon Emission Computerised Tomography scan.

How does it work? PET and SPECT scans are types of nuclear imaging. They use small amounts of radioactive material, called radio tracers, that are detected by the camera and then sent to a computer.

What does it scan? While CT and MRI scans show the structure of a body part, PET and SPECT scans can see how well it is functioning, such as measuring blood flow, and oxygen use.

What can it reveal to the doctor?

  • Cancer
  • Brain tumours
  • Seizures
  • Heart disease
  • Memory disorders such as Alzheimer’s.

What to expect from the PET/SPECT Scan? Radiotracers are injected, swallowed or inhaled before the scan. The tracers go to the body part being examined, and cameras detect and capture this. Because of the radiotracers, there is a low exposure to radiation, however, this risk is far outweighed by the potential information provided by the scan.