PET (or Positron Emission Tomography) is a branch of Nuclear Medicine imaging that uses special radio-active materials (positrons), in conjunction with a low-dose CT scan, to produce three dimensional images of the body.

PET is a very specialised imaging technique that has various roles including aiding in the detection of cancer, staging cancers prior to surgery, monitoring the response to chemotherapy and also detecting the recurrence of tumours.

It is most commonly used for tumours like lymphoma, melanoma, bowel and oesophageal cancer and head and neck tumours but can be useful in a wide variety of other tumours and occasionally heart and brain imaging.

The radioactive tracer used for PET scans is delivered on a daily basis. Due to it’s short active life, variables in manufacture and possible delays in transport which are beyond our control, we are unable to confirm scan times until the day before the appointment. Therefore, we need to be able to contact you at any time of the day before and the day of the appointment. If you miss your appointment time (or are late) we may have to reschedule your scan on a later day.



On arrival, you will go through a series of questions with a staff member. A plastic needle will be placed into a vein in your arm and your blood sugar level will be checked. You will then lie down in a special uptake room where the tracer will be injected in to your blood stream (through the needle in your arm). There are no side effects from this injection.

Once the injection has been given, you will be asked to rest quietly for an hour. During this time you may listen to music or watch TV, unless we are scanning your brain.

After the uptake hour, the PET scan will be performed. This takes around 30 minutes.

The total duration of the test that you will need to be in the department is 2 – 2.5 hours


You are required to fast for 6 hours before your PET examination and are also required to drink at least 500ml of water before coming in for the test (though you may still go to the toilet).

You should also not undertake strenuous work or exercise for 24 hours before the test.

If you are diabetic, please let us know when you book in for the test as we may need to make special arrangements regarding your diabetic medications.

We will usually contact you the day before the test to confirm your appointment (the tracer we use is ordered in specially for each test and is expensive).

If you suffer from severe claustrophobia, please discuss with us prior to your scan. If sedation is required, you will need to arrange for someone to drive you home.

After the scan you may eat and drink as normal. If you were given sedation for the scan, you will need to arrange for someone to drive you home.

Side Effects

The injection does not hurt and there is no iodine in it so you should not have any flushing or funny feelings. Side effects such as nausea, vomiting or a rash are very uncommon, occurring in approximately 1 in 10,000 people. After the procedure you are able to drive a car and eat and drink normally.

Pregnancy and / or Breastfeeding

If there is a possibility of pregnancy we prefer to delay the test unless it is absolutely necessary.

If you are breastfeeding we may reduce the dose of tracer administered and you will need to cease breastfeeding for 12 hours.

Radioactive Tracer

The radioactive tracer breaks down by itself in a short time. By the time you leave the department, over half will have already left your body. By the end of the day, most of the tracer will be gone. The radiation dose is equivalent to having a diagnostic CT scan.