What is a CT scan?

A computed tomography (CT) scan is a type of x-ray that creates 2- (2D) or 3-dimensional (3D) images of your body. It's also known as a computed axial tomography (CAT) scan.

CT scans provide more details than an x-ray. Your doctor may organise a CT scan to look at your soft body tissues. Soft tissues don't always show up on x-rays.

Because CT scans take many x-rays images, they use a higher level of radiation.

What are the benefits of a CT scan?

CT scans can help a doctor see different parts of your body, such as your:

• bones
• organs such as the brain
• soft tissues
• blood vessels

CT scans can help diagnose medical conditions such as an internal injury from an accident. Diagnosing a condition allows doctors to properly treat it.

Why would I need a CT scan?

A CT scan may be used to:

• look at the structure and anatomy (shape) of parts of your body
• diagnose and monitor different conditions such as a tumour or an infection
• check for injuries after a serious accident
• help plan treatment such as surgery or radiotherapy
• help guide doctors doing a biopsy

Any part of your body can be scanned, such as your:

• head
• chest
• abdomen
• pelvis

Your dentist may also use a special type of CT scan, known as cone beam CT scan (CBCT).

Your doctor may arrange a CT scan if an x-ray shows something that needs to be shown in more detail.

What does a CT scan involve?

When you have a CT scan, a ring-shaped machine moves around you in a circle. While it's moving, it takes x-rays of very thin 'slices' of your body.

A computer can then turn the x-ray images into 3D images. This means that a CT scan gives a view of the inside of your body from different angles.

Where can I get a CT scan?

You can get a CT scan at a hospital or radiology practice. You will need a referral from your doctor before booking an appointment.

How can I prepare myself for a CT scan?

The hospital or radiology practice will send you instructions before your CT scan.

You may need to have a special dye called contrast material. This is given by mouth or by injection. Contrast material is not radioactive. It helps to show your blood vessels and some organs in the scan.

If contrast material is needed, you may have to fast (not eat or drink) before your scan.

During the scan, you will need to lie very still.

If your child needs a CT scan, you can help them practise lying still at home, before their appointment.

What does a CT scan feel like?

The way a CT scan is done depends on the reason for your scan.

Before the scan

Before the scan, you may be injected with contrast material. You may feel some strange feelings from the contrast, like:

• a metallic taste in your mouth
• warm flushes
• feeling like you have wet yourself

These effects should only last for about 20 seconds.

During the scan

You'll usually lie on your back, on a flat bed that goes into the CT scanner. The scanner will rotate around a section of your body as you go through it.

While each scan is taken, you'll need to lie very still and breathe normally. This is so that the images are clear. At certain points in the exam, you may be asked to:

• breathe in
• breathe out
• hold your breath

A CT scan usually takes around 10 to 30 minutes. Most of this time is getting ready for the scan. The scan itself is quite quick.

How soon will I recover

You can usually go home soon after your scan.

Your doctor will talk with you about the results of your scan.

Are there complications of a CT scan?

Talk with your doctor about any risks and benefits of you having a CT.

Allergic reaction

There is a small chance of having an allergic reaction to the contrast material. This may cause symptoms such as:

• a rash
• itchiness
• nausea (feeling sick)
• sweating
• difficulty breathing

If you notice these symptoms during your CT scan, let the radiographer know.

Tell your doctor If you know you have an allergy to contrast material.

Radiation exposure

CT scans use x-rays which are a type of radiation that has been linked to cancer.

CT scans produce more radiation than other types of imaging. If you have a lot of CT scans, you may be at more risk.

Children are more sensitive to radiation as their bodies are still developing.

If your child needs a CT scan, check with the radiographer that they will get a 'kid-sized' radiation dose.

To lower the risks, CT scans should only be used when needed.

Pregnancy

If you're pregnant, or think you might be pregnant, talk to your doctor.

CT scans are best avoided in pregnancy. This is because there is a small chance that the radiation could harm your unborn baby.

Are there alternatives to a CT scan?

Your doctor may consider other types of imaging such as ultrasound and magnetic resonance imaging (MRI).

These tests don't use radiation but they may not give your doctor the information they need.

If you have any questions about CT scans, ask your doctor or radiographer. You can ask them:

• about the benefits and risks of the CT scan
• how to prepare for a CT scan
• what other imaging options could be used, such as an ultrasound
• if you have any older scans that could provide the information needed

What will happen if I decide not to have the CT scan?

If you decide not to have a CT scan this may affect the type of care you will receive.

CT scans can help identify health problems early when you can be easily treated. Delaying a CT scan may mean that you will need more treatment, and it may be harder to recover.

Resources and support

Inside Radiology has a lot of information about CT scans.

Visit Australian Commission on Safety and Quality in Health Care (the Commission) for more information about safety and risks of CT scans.

For more information about CT scans for children visit Australian Radiation Protection and Nuclear Safety Agency (ARPANSA).

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.