Matawai irirangi ā-rorohiko CT (computed tomography) scan

A CT scan gives much more detailed images than normal x-rays. CT can show the detail of bones, organs and some soft tissue. CT scans are used when this detail is needed.

Normal x-rays are best used to look at your bones and sometimes to see changes in your lungs. There are special types of x-ray used for other purposes, like the mammograms used to detect breast cancer.

You will be asked to lie on a motorised table for your CT scan. The table slides into the opening of a large, ring-shaped scanner. The scanner produces x-rays and has detectors that rotate around the ring. You will hear a whirring noise as they rotate.

The person doing the scan will be able to see and hear you at all times. You can speak with them through an intercom. It is important to stay as still as you can throughout the scan.

CT scans in children

Your healthcare provider may recommend a CT scan to help understand what is happening inside your child's body. KidsHealth has information on CT scans for tamariki and how to prepare them.

CT scans for children — KidsHealth (external link)

You will usually not need to do anything to prepare for your CT scan.

But for some scans you will need to fast (not eat or drink) before your appointment. Fasting for 2 to 4 hours is common.

You might be told to fast if your scan needs you have a contrast dye injected into a vein. Fasting makes it less likely the dye causes you to feel sick (nausea) or throw up (vomit). You will get instructions on what you need to do when you get your appointment letter.

Unless you have been told not to take them, you should take all your normal medications on the day of your CT scan.

If you are pregnant or think you may be pregnant, discuss this with your healthcare provider and the staff performing the CT scan. You will not be able to have a CT scan if you are pregnant — the radiation could harm your pēpi. Your healthcare provider will decide on what other tests they could do.

Contrast dye for CT scans

For some CT scans you may need an injection or drink of contrast dye before the scan. This is an iodine solution that helps highlight some of your body's internal structures. It is usually injected into a vein in your arm through a small plastic tube — you may feel a warm flush through your body during the injection.

Iodine-containing contrast medium — Inside Radiology (external link)

A specialist doctor (radiologist) will view the images and write a report about what the CT scan shows. They will send their report to the healthcare provider who requested your test.

You will be able to discuss the scan results with your healthcare provider at a follow-up appointment, over the phone or by email or text message.

A CT scan uses a small amount of radiation. It is more than you would get from a normal x-ray but it is still a small amount. The low dose of radiation you are exposed to during a CT scan has not been shown to cause harm.

Radiation risk of medical imaging for adults and children — Inside Radiology (external link)

If you have a contrast dye injection there is a small chance of an allergic reaction. This is usually mild, but if you have a more severe reaction the staff doing the CT scan will treat it.

You will need to be referred for a CT scan by your healthcare provider. You cannot self-refer.

This procedure can be done in the public health system or privately.