PET-CT (positron emission tomography and CT) scan

A PET scan shows areas in the body where cells are very active. This makes it particularly useful for showing up cancer, as cancer cells are very active cells.

A PET scan can also be used to look for other types of abnormal function in your body's tissues and organs.

You might have a PET scan to check to see if treatment you have been having has worked to slow down the activity or growth of the cells.

PET scans and CT scans are often used together (PET-CT scans) to assess cancers, brain diseases and heart-related diseases.

CT (computed tomography) scan

A PET scan usually examines your whole body, from your head to your thighs. Sometimes it scans just certain organs such as your brain or heart.

PET and CT scans can be combined

Images from the PET scanner are often combined with those from a CT scanner. They are taken at the same time. The combined images (PET-CT) allow diseases to be detected and located more accurately.

PET scans use a radiotracer

A radiotracer is what shows up on the PET scan. The radiotracer is injected into a vein in your arm. It travels around your body and gathers in areas where there is higher metabolic activity. These are areas where the cells are very active, which might mean the cells are growing or multiplying.

Different types of radiotracers can be used, depending on the reason for the scan. If the radiotracer targets a specific disease, it accumulates in parts of your body where that disease is most concentrated.

The radiation released by the radiotracer is picked up by a PET camera. A computer then produces images of the area being scanned.

CT scans may use a contrast dye

You may need to have an injection of a contrast dye for the CT scan that is done with your PET scan.

A few people can react to the contrast dye. You will be asked about any previous experiences you have had with iodine contrast before you have your scan.

Iodine-containing contrast medium — Inside Radiology

You will usually be given the radiotracer injection 45 to 60 minutes before your scan. You will need to rest quietly while it circulates around your body.

Then you will lie on a padded table that slides into the short tunnel of the PET-CT scanner. The scanner is reasonably quiet most of the time, and painless. It is important you keep very still so the images are clear.

The whole process usually takes up to 2 hours.

Tell your healthcare provider if you:

• have ever had an allergic reaction to a CT contrast dye
• have recently been unwell
• have a medical condition, for example, diabetes, kidney disease or asthma
• are taking any medicines, herbal supplements or vitamins
• are pregnant or might be pregnant
• are breastfeeding
• get scared of small spaces (claustrophobic).

When you get your appointment time, you will be given instructions on what you need to do to prepare for your scan. You will usually be asked to:

• avoid strenuous exercise for a couple of days before your scan
• stop eating 4 hours before your scan (you can still drink water).

• The amount of radioactive tracer used for your PET scan is small and will flush out of your body in your wee in a few hours.
• Drinking plenty of fluids will help to flush the tracer out of your body.
• During these few hours, it is recommended that you limit contact with others until the radiotracer has been flushed out.
• You may be advised to limit contact with tamariki and pregnant women until the following day.
• You can get back to your usual activities and eating straight after the scan.

A specialist doctor (radiologist) will view the images and write a report about what the scan shows.

The radiologist will send their report to the healthcare provider who asked for the test. They will then discuss the test results with you during a follow-up appointment, over the phone or by email or text message.

A PET-CT scan is a safe procedure. There are no known serious complications of the scan.

The radioactivity is from a safe type of chemical and only a very tiny amount is used.

If you are pregnant or think you might be pregnant, or are breastfeeding, you should tell your healthcare provider. They will let you know if you need to take any precautions, delay the scan or have a different test instead.

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 CT staff will treat it.

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

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