HealthInfo Waitaha Canterbury
PET-CT (positron emission tomography and CT) scan
A PET (positron emission tomography) scan uses a special type of camera that detects radiation and a small amount of a radioactive substance (called a radiotracer). The scan is used to pick up disease or abnormal function in your tissues and organs.
A PET scan usually examines your entire body from skull to thighs, but some PET scans can be limited to certain organs such as your brain or heart. Different types of radiotracers are used depending on the reason for the scan.
During the test, the radiotracer is injected into a vein in your arm. As it travels around your body, it accumulates in areas where there is a higher level of metabolic activity. If a disease-specific radiotracer has been used, it accumulates in parts of your body where there is a high concentration of the disease being examined. The radiation released by the radiotracer is detected by a PET camera and a highly sophisticated computer reconstruction then produces images of the area being examined.
Images from the PET scanner are generally combined with those of a CT scanner taken at the same time. The combined images (PET-CT) allow more accurate detection and location of disease.
PET-CT scans are mainly done to assess cancers, brain diseases and heart-related diseases.
Before Your Scan
Tell your healthcare provider if:
- you've ever had an allergic reaction to a CT contrast dye
- you've recently been sick
- you have a medical condition, for example, diabetes, kidney disease or asthma
- you're taking any medicines, herbal supplements or vitamins
- you're pregnant or might be pregnant
- you're breastfeeding
- you get claustrophobic (scared of small spaces).
When you get your appointment time, you'll be given instructions on what you need to do to prepare for your scan. You'll usually be asked to:
- avoid strenuous exercise for a couple of days before your scan
- stop eating four hours before your scan.
During your scan
Generally, you'll be given the radiotracer injection 45 to 60 minutes before your scan and will have to rest quietly while the tracer circulates within your body (this is called the uptake time).
After the uptake time, you'll lie on a padded table that slides into the short tunnel of the PET-CT scanner. It's important that you keep very still so the images aren't blurry. The scanner is relatively quiet most of the time and you will not feel any pain during the scan.
You may need to have an injection of a contrast dye for the CT scan accompanying your PET scan. As a few people react to the contrast dye, you'll be asked about any previous experiences you've had with iodine contrast before you have your scan.
The contrast dye for the CT scan may give you a momentary warm sensation through your body or metallic taste in your mouth.
The entire procedure usually takes up to two hours.
After your Scan
- The amount of radioactive tracer used during the PET scan is small and will be flushed out of your system in a few hours. During this time, it's recommended that you minimise contact with others.
- You may be advised to minimise contact with children and pregnant women until the following day.
- Drinking plenty of fluids will help to flush the tracer out of your body.
- 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. They will send their report to the health professional who asked for the test, who will then discuss the test results with you during a follow-up appointment, over the phone or by email or text message.
Risks of the scan
A PET-CT scan is a safe procedure that is regularly performed all around the world. There are no known serious complications of the scan.
If you need 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.
HealthInfo recommends the following pages
- Royal Australian and New Zealand College of Radiologists
- Computed tomography (CT)
This page has more detailed information about CT scans.
- PET scan
This page has more detailed information about PET-CT scans.
- Computed tomography (CT)
Content shared between HealthInfo Canterbury, KidsHealth and Health Navigator NZ as part of a National Health Content Hub collaborative. Page created December 2022.
SourcesReview key: HISXN-86976
